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1.
Cureus ; 16(5): e59717, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38841005

RESUMO

Interscalene nerve block (ISB) is an effective and low-risk local anesthetic (LA) procedure that is commonly employed for shoulder surgery. While phrenic nerve involvement occurs to some degree in every ISB procedure, the incidence of hypoxemia and other clinical signs of diaphragmatic disruption is much lower. This is a case of a 36-year-old female with no underlying respiratory disease who developed hypoxemia requiring a night of observation following an ISB for a rotator cuff repair procedure in an ambulatory surgical center. Her hypoxemia was easily treated with supplemental oxygen and she made a full recovery by the next day. The use of ultrasound guidance, reduced LA volume, less potent medication, sterile fluid for optimal visualization, and extrafascial administration should be considered for all patients receiving an ISB to prevent respiratory complications.

2.
Cureus ; 16(4): e58042, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38738030

RESUMO

Glucagon-like peptide-1 (GLP-1) agonists are very popular and useful medications for the treatment of type 2 diabetes mellitus and obesity. Potent gastric emptying delay is common with these medications, serving as a major contributor to the postprandial glycemic control and weight loss benefits of these medications. Recently, multiple case reports and studies indicating safety risks for these medications and their use in patients planning to undergo general anesthesia have been published, as retained gastric contents can lead to intraoperative aspiration. New guidelines for these medications have been released to guide clinical practice for anesthesiologists. Some degree of preoperative cessation of these medications is required. At this time, the ideal window for cessation of these medications to optimize clinical efficacy while reducing aspiration risks has not yet been well elaborated on. Aspiration of gastric contents can still occur despite appropriate preoperative fasting in patients taking GLP-1 agonists. Gastric ultrasound appears to be an effective and objective way of preoperatively assessing a patient's stomach contents to make decisions regarding anesthetic management for patients prescribed these medications. This practice is limited by a general lack of training and implementation in current anesthesiology practice.

3.
Anticancer Res ; 44(5): 1807-1815, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38677738

RESUMO

BACKGROUND/AIM: Recently developed vaccines for the SARS-CoV-2 virus utilize endogenous production of the virus' spike protein (SP), allowing the host to develop an immune response. As a result of the novelty of this virus and its vaccines, little is known overall about the potential effects of the SP on the pathogenesis of neoplasia, either from vaccination or from infection. This study was designed to investigate whether SARS-CoV-2 SP has any direct effect on SiHa cervical cancer cells. MATERIALS AND METHODS: The effects of SARS-CoV-2 SP on cervical cancer cell proliferation and apoptosis were investigated by using clonogenic cell survival assay, quick cell proliferation assay, and caspase-3 activity kits in a widely-used cervical cancer cell line, SiHa. RT-PCR and immunohistochemistry were also performed to determine the potential molecular mechanisms. RESULTS: The growth and proliferation of SiHa cancer cells were inhibited by SARS-CoV-2 SP. SARS-CoV-2 SP also induced apoptosis in SiHa cancer cells. The anti-proliferative effect of SARS-CoV-2 SP on SiHa cancer cells was associated with the up-regulation of the anti-proliferative molecule p53. The pro-apoptotic effect of SARS-CoV-2 SP on SiHa cells was associated with the up-regulation of the pro-apoptotic molecule TRAIL. CONCLUSION: SARS-CoV-2 SP inhibits the growth of cervical cancer via up-regulation of p53 and TRAIL. Further studies are needed to elaborate on the potential effects of the SARS-CoV-2 SP on other cancer cell lines and normal physiological cell lines for comparison.


Assuntos
Apoptose , Proliferação de Células , SARS-CoV-2 , Glicoproteína da Espícula de Coronavírus , Neoplasias do Colo do Útero , Humanos , Neoplasias do Colo do Útero/virologia , Neoplasias do Colo do Útero/patologia , Neoplasias do Colo do Útero/metabolismo , Feminino , Glicoproteína da Espícula de Coronavírus/metabolismo , Glicoproteína da Espícula de Coronavírus/genética , Linhagem Celular Tumoral , SARS-CoV-2/fisiologia , COVID-19/virologia , COVID-19/metabolismo , COVID-19/patologia , Proteína Supressora de Tumor p53/metabolismo , Caspase 3/metabolismo
4.
Wiley Interdiscip Rev RNA ; 15(2): e1832, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38448799

RESUMO

MicroRNAs (miRNAs) are small non-coding RNAs that play a fundamental role in enabling miRNA-mediated target repression, a post-transcriptional gene regulatory mechanism preserved across metazoans. Loss of certain animal miRNA genes can lead to developmental abnormalities, disease, and various degrees of embryonic lethality. These short RNAs normally guide Argonaute (AGO) proteins to target RNAs, which are in turn translationally repressed and destabilized, silencing the target to fine-tune gene expression and maintain cellular homeostasis. Delineating miRNA-mediated target decay has been thoroughly examined in thousands of studies, yet despite these exhaustive studies, comparatively less is known about how and why miRNAs are directed for decay. Several key observations over the years have noted instances of rapid miRNA turnover, suggesting endogenous means for animals to induce miRNA degradation. Recently, it was revealed that certain targets, so-called target-directed miRNA degradation (TDMD) triggers, can "trigger" miRNA decay through inducing proteolysis of AGO and thereby the bound miRNA. This process is mediated in animals via the ZSWIM8 ubiquitin ligase complex, which is recruited to AGO during engagement with triggers. Since its discovery, several studies have identified that ZSWIM8 and TDMD are indispensable for proper animal development. Given the rapid expansion of this field of study, here, we summarize the key findings that have led to and followed the discovery of ZSWIM8-dependent TDMD. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Turnover and Surveillance > Turnover/Surveillance Mechanisms RNA in Disease and Development > RNA in Development.


Assuntos
MicroRNAs , Riboswitch , Animais , MicroRNAs/genética , Interferência de RNA , Proteínas Argonautas/genética
5.
bioRxiv ; 2023 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-37873200

RESUMO

Glioblastomas (GBMs) are highly aggressive, infiltrative, and heterogeneous brain tumors driven by complex driver mutations and glioma stem cells (GSCs). The neurodevelopmental transcription factors ASCL1 and OLIG2 are co-expressed in GBMs, but their role in regulating the heterogeneity and hierarchy of GBM tumor cells is unclear. Here, we show that oncogenic driver mutations lead to dysregulation of ASCL1 and OLIG2, which function redundantly to initiate brain tumor formation in a mouse model of GBM. Subsequently, the dynamic levels and reciprocal binding of ASCL1 and OLIG2 to each other and to downstream target genes then determine the cell types and degree of migration of tumor cells. Single-cell RNA sequencing (scRNA-seq) reveals that a high level of ASCL1 is key in defining GSCs by upregulating a collection of ribosomal protein, mitochondrial, neural stem cell (NSC), and cancer metastasis genes - all essential for sustaining the high proliferation, migration, and therapeutic resistance of GSCs.

6.
Mol Cell ; 83(21): 3818-3834.e7, 2023 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-37820733

RESUMO

N6-methyladenosine (m6A) modifications play crucial roles in RNA metabolism. How m6A regulates RNA polymerase II (RNA Pol II) transcription remains unclear. We find that 7SK small nuclear RNA (snRNA), a regulator of RNA Pol II promoter-proximal pausing, is highly m6A-modified in non-small cell lung cancer (NSCLC) cells. In A549 cells, we identified eight m6A sites on 7SK and discovered methyltransferase-like 3 (METTL3) and alkB homolog 5 (ALKBH5) as the responsible writer and eraser. When the m6A-7SK is specifically erased by a dCasRx-ALKBH5 fusion protein, A549 cell growth is attenuated due to reduction of RNA Pol II transcription. Mechanistically, removal of m6A leads to 7SK structural rearrangements that facilitate sequestration of the positive transcription elongation factor b (P-TEFb) complex, which results in reduction of serine 2 phosphorylation (Ser2P) in the RNA Pol II C-terminal domain and accumulation of RNA Pol II in the promoter-proximal region. Taken together, we uncover that m6A modifications of a non-coding RNA regulate RNA Pol II transcription and NSCLC tumorigenesis.


Assuntos
Carcinoma Pulmonar de Células não Pequenas , Neoplasias Pulmonares , Humanos , RNA Polimerase II/genética , RNA Polimerase II/metabolismo , Carcinoma Pulmonar de Células não Pequenas/genética , Fator B de Elongação Transcricional Positiva/genética , Neoplasias Pulmonares/genética , RNA Nuclear Pequeno/genética , Transcrição Gênica , Células HeLa , Metiltransferases/genética , Metiltransferases/metabolismo
7.
Cureus ; 15(3): e35795, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37025738

RESUMO

Squamous cell carcinoma of the gallbladder is a profoundly rare tumor. It is one of the most aggressive and deadly forms of gallbladder cancer, often being diagnosed at a later stage. There are no definitive risk factors described for this specific type of gallbladder tumor when compared to other forms of gallbladder carcinoma. This case is regarding a 64-year-old female who was found to have primary squamous cell carcinoma of the gallbladder during an attempted cholecystectomy. Her tumor was found to have invaded her liver. The tumor displayed characteristic qualities of a pure squamous cell carcinoma and was positive for CK7 and p63 upon pathological analysis. Best results for treatment for this condition are achieved via R0 resection. Adjuvant therapy with chemoradiation has not been well-defined nor very effective in prior cases.

8.
PLoS One ; 18(3): e0279144, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36928885

RESUMO

Early Plasmodium falciparum and P. vivax infection requires parasite replication within host hepatocytes, referred to as liver stage (LS). However, limited understanding of infection dynamics in human LS exists due to species-specificity challenges. Reported here is a reproducible, easy-to-manipulate, and moderate-cost in vivo model to study human Plasmodium LS in mice; the ectopic huLiver model. Ectopic huLiver tumors were generated through subcutaneous injection of the HC-04 cell line and shown to be infectible by both freshly dissected sporozoites and through the bite of infected mosquitoes. Evidence for complete LS development was supported by the transition to blood-stage infection in mice engrafted with human erythrocytes. Additionally, this model was successfully evaluated for its utility in testing antimalarial therapeutics, as supported by primaquine acting as a causal prophylactic against P. falciparum. Presented here is a new platform for the study of human Plasmodium infection with the potential to aid in drug discovery.


Assuntos
Doenças Transmissíveis , Hepatopatias , Malária Falciparum , Malária Vivax , Malária , Plasmodium , Camundongos , Animais , Humanos , Fígado/parasitologia , Malária/tratamento farmacológico , Malária Falciparum/parasitologia , Hepatócitos/parasitologia , Plasmodium falciparum , Esporozoítos
9.
Physiother Theory Pract ; 39(11): 2490-2500, 2023 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-35608622

RESUMO

BACKGROUND: End-stage ankle osteoarthritis is one of the leading causes of chronic disability in North America. The main purpose of this case report was to describe the functional recovery of a person following total ankle arthroplasty (TAA) surgery using the INFINITY™ system for end stage osteoarthritis of the left ankle. CASE DESCRIPTION: We report a case of a 55-year-old male who had attempted conservative management for end stage ankle osteoarthritis in his left ankle but ultimately elected to undergo TAA using The INFINITY™ Total Ankle System. He not only had significant left ankle pain limiting his daily function, but also had developed severe right knee pain. We performed gait analysis both before and 6 months after his TAA surgery to examine the sagittal and frontal-plane motions of bilateral ankle, knee, and hip joints during gait. OUTCOMES: At 6 months post-surgery, the patient demonstrated a 44-point improvement in his Foot and Ankle Outcome questionnaire scores as well as an increase in both left knee and left ankle motion in the sagittal and frontal planes. Kinematic deviations in the left ankle, hip, and knee joints during gait also reduced post-surgery. Despite improvement in his left ankle and overall function, the participant's right knee pain and altered kinematics of the right limb during gait worsened after surgery. DISCUSSION: Interventions, either before or after ankle surgery, should consider bilateral lower extremities simultaneously in order to optimize patient care and minimize future secondary complications for individuals with unilateral ankle osteoarthritis.


Assuntos
Artroplastia de Substituição do Tornozelo , Osteoartrite , Masculino , Humanos , Pessoa de Meia-Idade , Tornozelo/cirurgia , Marcha , Articulação do Tornozelo/cirurgia , Extremidade Inferior , Fenômenos Biomecânicos , Amplitude de Movimento Articular
10.
J Robot Surg ; 17(3): 719-743, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36413255

RESUMO

The use of robotic surgery has increased exponentially in the United States. Despite this uptick in popularity, no standardized training pathway exists for surgical residents or practicing surgeons trying to cross-train onto the platform. We set out to perform a systematic review of existing literature to better describe and analyze existing robotic surgical training curricula amongst academic surgery programs. A systematic electronic search of the PubMed, Cochrane, and EBSCO databases was performed for articles describing simulation in robotic surgery from January 2010 to May 2022. Medical Subject Heading (MeSH) terms and keywords used to conduct this search were "Robotic," "Surgery," "Robotic Surgery," "Training," "Curriculum," "Education," and "Residency Program." A total of 110 articles were identified for the systematic review. After screening the titles and abstracts, a total of 36 full-text original articles were included in this systematic review. Of these, 24 involved robotic surgery curricula designed to teach general robotic skills, whereas the remaining 12 were for teaching procedure specific skills. Of the 24 studies involving general robotic skills, 13 included didactics as a part of the curriculum, 23 utilized virtual reality trainers, 3 used inanimate tissue, and 1 used live animal models. Of the 12 papers reviewed regarding procedure specific curricula, seven involved urologic procedures (radical prostatectomy and nephrectomy), two involved general surgical procedures (colectomy and Roux-en-Y gastric bypass surgery), two involved obstetrics and gynecology procedures (hysterectomy with myomectomy and sacrocolpopexy, hysterectomy with pelvic lymphadenectomy) and one involved a cardiothoracic surgery procedure (robotic internal thoracic artery harvest). With the rapid implementation of robotic surgery, training programs have been tasked with the responsibility of ensuring their trainees are adequately proficient in the platform prior to graduation. However, due to the lack of uniformity between surgical training programs, when it comes to robotic surgical experience, a strong need persists for a standardized national robotics training curriculum.


Assuntos
Procedimentos Cirúrgicos Robóticos , Robótica , Humanos , Animais , Feminino , Gravidez , Masculino , Procedimentos Cirúrgicos Robóticos/métodos , Currículo , Colectomia , Simulação por Computador
11.
Glob Chang Biol ; 28(23): 7094-7107, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36107442

RESUMO

Mixotrophs, organisms that combine photosynthesis and heterotrophy to gain energy, play an important role in global biogeochemical cycles. Metabolic theory predicts that mixotrophs will become more heterotrophic with rising temperatures, potentially creating a positive feedback loop that accelerates carbon dioxide accumulation in the atmosphere. Studies testing this theory have focused on phenotypically plastic (short-term, non-evolutionary) thermal responses of mixotrophs. However, as small organisms with short generation times and large population sizes, mixotrophs may rapidly evolve in response to climate change. Here, we present data from a 3-year experiment quantifying the evolutionary response of two mixotrophic nanoflagellates to temperature. We found evidence for adaptive evolution (increased growth rates in evolved relative to acclimated lineages) in the obligately phototrophic strain, but not in the facultative phototroph. All lineages showed trends of increased carbon use efficiency, flattening of thermal reaction norms, and a return to homeostatic gene expression. Generally, mixotrophs evolved reduced photosynthesis and higher grazing with increased temperatures, suggesting that evolution may act to exacerbate mixotrophs' effects on global carbon cycling.


Assuntos
Aclimatação , Fotossíntese , Temperatura , Processos Heterotróficos/fisiologia , Ciclo do Carbono
12.
Acc Chem Res ; 54(19): 3710-3719, 2021 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-34565142

RESUMO

Redox reactions that take place in enzymes and on the surfaces of heterogeneous catalysts often require active sites that contain multiple metals. By contrast, there are very few homogeneous catalysts with multinuclear active sites, and the field of organometallic chemistry continues to be dominated by the study of single metal systems. Multinuclear catalysts have the potential to display unique properties owing to their ability to cooperatively engage substrates. Furthermore, direct metal-to-metal covalent bonding can give rise to new electronic configurations that dramatically impact substrate binding and reactivity. In order to effectively capitalize on these features, it is necessary to consider strategies to avoid the dissociation of fragile metal-metal bonds in the course of a catalytic cycle. This Account describes one approach to accomplishing this goal using binucleating redox-active ligands.In 2006, Chirik showed that pyridine-diimines (PDI) have sufficiently low-lying π* levels that they can be redox-noninnocent in low-valent iron complexes. Extending this concept, we investigated a series of dinickel complexes supported by naphthyridine-diimine (NDI) ligands. These complexes can promote a broad range of two-electron redox processes in which the NDI ligand manages electron equivalents while the metals remain in a Ni(I)-Ni(I) state.Using (NDI)Ni2 catalysts, we have uncovered cases where having two metals in the active site addresses a problem in catalysis that had not been adequately solved using single-metal systems. For example, mononickel complexes are capable of stoichiometrically dimerizing aryl azides to form azoarenes but do not turn over due to strong product inhibition. By contrast, dinickel complexes are effective catalysts for this reaction and avoid this thermodynamic sink by binding to azoarenes in their higher-energy cis form.Dinickel complexes can also activate strong bonds through the cooperative action of both metals. Norbornadiene has a ring-strain energy that is similar to that of cyclopropane but is not prone to undergoing C-C oxidative addition with monometallic complexes. Using an (NDI)Ni2 complex, norbornadiene undergoes rapid ring opening by the oxidative addition of the vinyl and bridgehead carbons. An inspection of the resulting metallacycle reveals that it is stabilized through a network of secondary Ni-π interactions. This reactivity enabled the development of a catalytic carbonylative rearrangement to form fused bicyclic dienones.These vignettes and others described in this Account highlight some of the implications of metal-metal bonding in promoting a challenging step in a catalytic cycle or adjusting the thermodynamic landscape of key intermediates. Given that our studies have focused nearly exclusively on the (NDI)Ni2 system, we anticipate that many more such cases are left to be discovered as other transition-metal combinations and ligand classes are explored.


Assuntos
Complexos de Coordenação/química , Iminas/química , Níquel/química , Piridinas/química , Complexos de Coordenação/síntese química , Ligantes , Estrutura Molecular , Oxirredução
13.
BMC Pulm Med ; 21(1): 223, 2021 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-34247594

RESUMO

BACKGROUND: Ciliated muconodular papillary tumor (CMPT) is an incredibly rare pulmonary tumor. Currently, little is known about CMPT, and it has not yet been classified by the World Health Organization. The clinical manifestation of CMPT is nonspecific and the diagnosis is only based on pathology. CMPT has been documented in limited reports as a benign tumor, thus the treatment is typically with surgical excision if a solid tumor is identifiable. The prognosis of CMPT is very positive, as no recurrence has been reported in the limited literature available. However, CMPT accompanied with adenocarcinoma in situ has not been reported previously in the literature. CASE PRESENTATION: In this report, we presented a case of a 53-year-old male smoker with CMPT associated with adenocarcinoma in situ. This diagnosis was confirmed by pathological examination, including immunohistostaining. No solid resectable lesion was identified on CT scan; therefore, no surgery was performed. The patient's adenocarcinoma in situ was disseminated in both lungs, thus chemotherapeutic treatment with cisplatin and pemetrexed was given. The patient will be continually followed up closely on a wait-and-watch basis. CONCLUSIONS: In summary, our report reveals a unique case of CMPT in conjunction with adenocarcinoma in situ, potentially revealing an association between CMPT and malignancy which has not been previously reported. More similar case studies will be beneficial to determine the authentic relationship between CMPT and adenocarcinoma in situ.


Assuntos
Adenocarcinoma in Situ/patologia , Carcinoma Papilar/patologia , Neoplasias Pulmonares/patologia , Adenocarcinoma in Situ/diagnóstico por imagem , Antineoplásicos/uso terapêutico , Carcinoma Papilar/tratamento farmacológico , Cisplatino/uso terapêutico , Humanos , Neoplasias Pulmonares/tratamento farmacológico , Masculino , Pessoa de Meia-Idade , Pemetrexede/uso terapêutico , Tomografia Computadorizada por Raios X , Resultado do Tratamento
14.
Anticancer Res ; 41(7): 3337-3341, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34230129

RESUMO

BACKGROUND/AIM: Glioblastoma, also known as glioblastoma multiforme (GBM), is the most aggressive type of primary brain tumor and a cornerstone in its treatment is radiotherapy (RT). However, RT for GBM is largely ineffective at clinically safe doses, thus, the study of radiosensitizers is of great significance. MATERIALS AND METHODS: With accumulating evidence for the anticancer effect of compounds from cranberry, this study was designed to investigate if cranberry extract (CE) sensitizes GBM to RT in the widely used human glioblastoma cell line U87. We utilized clonogenic survival assays, cell proliferation assays, and caspase-3 activity kits. Potential proliferative and apoptotic molecular mechanisms were evaluated by reverse transcription-polymerase chain reaction. RESULTS: We found that CE alone had little effect on the survival of U87 cells. However, RT supplemented by CE significantly inhibited proliferation and promoted apoptosis of U87 cells when compared with RT alone. The proliferation-inhibitory effect of RT/CE might be attributable to the up-regulation of p21, along with the down-regulation of cyclin B and cyclin-dependent kinase 4. This pro-apoptotic effect might additionally be attributable to the down-regulation of survivin. CONCLUSION: These results warrant further study of the potential radiosensitizing capacity of CE in glioblastoma and other cancer types.


Assuntos
Neoplasias Encefálicas/tratamento farmacológico , Glioblastoma/tratamento farmacológico , Extratos Vegetais/farmacologia , Radiossensibilizantes/farmacologia , Vaccinium macrocarpon/química , Apoptose/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Regulação para Baixo/efeitos dos fármacos , Humanos , Regulação para Cima/efeitos dos fármacos
15.
Cancer Lett ; 518: 94-101, 2021 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-34153401

RESUMO

In recent years, tumor metabolism has become a prevalent research topic for scientists and pharmaceutical companies. As research in the field has progressed, the metabolism-based therapy of tumors has ushered in new opportunities. Most tumors emerge and evolve under selective pressure from their microenvironment, which promotes the diversification of both neoplastic and non-neoplastic compartments of the tumor microenvironment (TME), and finally reaches a certain degree of intratumoral heterogeneity. As a result of the tumor intratumoral heterogeneity, tumor cells often possess a complex energy metabolism phenotype. During tumor progression, the metabolism for both tumor parenchyma and stroma is reprogrammed. The tumor stroma mainly consists of the extracellular matrix, fibroblasts, and immune cells. Interestingly, tumor-infiltrating immune cells utilize different metabolites based on their subtype and function, and these immunometabolic pathways can be modified in the TME. In particular, interleukins play a vital role in the activation and differentiation of immune cells and have exhibited multiple effects on tumor cell neoplasia, invasion, and metastasis. In this review, we summarize the common mechanisms of interleukins affecting the tumor and tumor-infiltrating immune cells metabolically and discuss how these mechanisms may lead to novel therapeutic opportunities. This review might contribute to the novel development of cancer immunotherapy.


Assuntos
Interleucinas/imunologia , Interleucinas/metabolismo , Redes e Vias Metabólicas/imunologia , Neoplasias/imunologia , Neoplasias/metabolismo , Animais , Diferenciação Celular/imunologia , Metabolismo Energético/imunologia , Matriz Extracelular/imunologia , Matriz Extracelular/metabolismo , Humanos , Imunoterapia/métodos , Neoplasias/terapia , Microambiente Tumoral/imunologia
16.
J Phys Chem B ; 124(32): 6963-6971, 2020 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-32667795

RESUMO

Characterization of the internal mechanical state of model lipid membranes is essential to understand the microscopic underpinnings of biological functions such as membrane fission and organelle shaping within the context of elastic theories such as the Helfrich framework. Here, we compute lateral stress or pressure profiles from molecular dynamics simulations of lipid bilayers and water-vacuum interfaces to understand the role that solvent treatment and force-field parametrization plays on the local mechanical features of membranes. We focus on two atomistic models, GROMOS 43A1-S3 and CHARMM36, and several variants of the MARTINI coarse-grained force-field, including the single-bead nonpolar water, three-point polarizable water, big multipole water, and solvent-free variants. Our results show that the various atomistic and coarse-grained force-fields produce contrasting lateral stress profiles as a result of the balance of solvent-solvent and solvent-solute forces at the hydrocarbon-water interface and fundamentally different treatment of pairwise (e.g., van der Waals, Coulomb, etc.) and multibody interactions (angles and torsions). Numerical integration of the second moment of the bilayer stress profiles indicates that different local distributions of repulsive and attractive stresses across the membrane, due to distinct force-field parametrizations, may result in substantial variations in macroscopic elastic properties.


Assuntos
Bicamadas Lipídicas , Simulação de Dinâmica Molecular , Solventes , Termodinâmica , Água
17.
J Am Chem Soc ; 142(10): 4598-4603, 2020 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-32083863

RESUMO

Polysubstituted cyclohexenes bearing 1,3 (meta) substitution patterns are challenging to access using the Diels-Alder reaction (the ortho-para rule). Here, we report a cobalt-catalyzed reductive [5 + 1]-cycloaddition between a vinylcyclopropane and a vinylidene to provide methylenecyclohexenes bearing all-meta relationships. Vinylidene equivalents are generated from 1,1-dichloroalkenes using Zn as a stoichiometric reductant. Experimental observations are consistent with a mechanism involving a cobaltacyclobutane formed from a [2 + 2]-cycloaddition between a cobalt vinylidene and a vinylcyclopropane.


Assuntos
Cicloexenos/síntese química , Ciclopropanos/química , Compostos de Vinila/química , Catálise , Cobalto/química , Complexos de Coordenação/química , Reação de Cicloadição , Modelos Químicos
18.
Proc Biol Sci ; 286(1916): 20192230, 2019 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-31771480

RESUMO

Extreme climatic events (ECEs) are increasing in frequency and intensity and this necessitates understanding their influence on organisms. Animal behaviour may mitigate the effects of ECEs, but field studies are rare because ECEs are infrequent and unpredictable. Hurricane Irma made landfall in southwestern Florida where we were monitoring white-tailed deer (Odocoileus virginianus seminolus) with GPS collars. We report on an opportunistic case study of behavioural responses exhibited by a large mammal during an ECE, mitigation strategies for reducing the severity of the ECE effects, and the demographic effect of the ECE based on known-fate of individual animals. Deer altered resource selection by selecting higher elevation pine and hardwood forests and avoiding marshes. Most deer left their home ranges during Hurricane Irma, and the probability of leaving was inversely related to home range area. Movement rates increased the day of the storm, and no mortality was attributed to Hurricane Irma. We suggest deer mobility and refuge habitat allowed deer to behaviourally mitigate the negative effects of the storm, and ultimately, aid in survival. Our work contributes to the small but growing body of literature linking behavioural responses exhibited during ECEs to survival, which cumulatively will provide insight for predictions of a species resilience to ECEs and improve our understanding of how behavioural traits offset the negative impacts of global climate change.


Assuntos
Comportamento Animal , Tempestades Ciclônicas , Cervos/fisiologia , Comportamento de Retorno ao Território Vital , Animais , Mudança Climática , Ecossistema , Florida
19.
Science ; 364(6441)2019 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-31097641

RESUMO

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU69 is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU69's origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

20.
J Am Chem Soc ; 140(40): 12710-12714, 2018 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-30216053

RESUMO

Cyclic structures are highly represented in organic molecules, motivating a wealth of catalytic methods targeting their synthesis. Among the various ring-forming processes, cyclooligomerization reactions possess several attractive features but require addressing a unique challenge associated with controlling ring-size selectivity. Here we describe the catalytic reductive cocyclooligomerization of an enone and three carbene equivalents to generate a cyclopentane, a process that constitutes a formal [2 + 1 + 1 + 1]-cycloaddition. The reaction is promoted by a (quinox)Ni catalyst and uses CH2Cl2/Zn as the C1 component. Mechanistic studies are consistent with a metallacycle-based pathway, featuring sequential migratory insertions of multiple carbene equivalents to yield cycloalkanes larger than cyclopropanes.


Assuntos
Reação de Cicloadição/métodos , Ciclopentanos/síntese química , Catálise , Ciclização , Ciclopentanos/química , Metano/análogos & derivados , Metano/síntese química , Metano/química , Modelos Moleculares , Níquel/química , Oxirredução
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