Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 5 de 5
Filtrar
1.
Nat Commun ; 14(1): 4687, 2023 08 22.
Artigo em Inglês | MEDLINE | ID: mdl-37607943

RESUMO

Tooth classes are an innovation that has contributed to the evolutionary success of mammals. However, our understanding of the mechanisms by which tooth classes diversified remain limited. We use the evolutionary radiation of noctilionoid bats to show how the tooth developmental program evolved during the adaptation to new diet types. Combining morphological, developmental and mathematical modeling approaches, we demonstrate that tooth classes develop through independent developmental cascades that deviate from classical models. We show that the diversification of tooth number and size is driven by jaw growth rate modulation, explaining the rapid gain/loss of teeth in this clade. Finally, we mathematically model the successive appearance of tooth buds, supporting the hypothesis that growth acts as a key driver of the evolution of tooth number and size. Our work reveal how growth, by tinkering with reaction/diffusion processes, drives the diversification of tooth classes and other repeated structure during adaptive radiations.


Assuntos
Quirópteros , Animais , Mamíferos/genética , Aclimatação , Difusão
2.
Small ; 5(1): 126-34, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19051182

RESUMO

This study evaluates the influence of particle size, PEGylation, and surface coating on the quantitative biodistribution of near-infrared-emitting quantum dots (QDs) in mice. Polymer- or peptide-coated 64Cu-labeled QDs 2 or 12 nm in diameter, with or without polyethylene glycol (PEG) of molecular weight 2000, are studied by serial micropositron emission tomography imaging and region-of-interest analysis, as well as transmission electron microscopy and inductively coupled plasma mass spectrometry. PEGylation and peptide coating slow QD uptake into the organs of the reticuloendothelial system (RES), liver and spleen, by a factor of 6-9 and 2-3, respectively. Small particles are in part renally excreted. Peptide-coated particles are cleared from liver faster than physical decay alone would suggest. Renal excretion of small QDs and slowing of RES clearance by PEGylation or peptide surface coating are encouraging steps toward the use of modified QDs for imaging living subjects.


Assuntos
Polietilenoglicóis/química , Pontos Quânticos , Animais , Fígado/metabolismo , Camundongos , Microscopia Eletrônica de Transmissão , Peso Molecular , Tamanho da Partícula , Peptídeos/química , Tomografia por Emissão de Pósitrons , Baço/metabolismo , Propriedades de Superfície
3.
J Nucl Med ; 48(9): 1511-8, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17704240

RESUMO

UNLABELLED: This study evaluates the quantitative biodistribution of commercially available CdSe quantum dots (QD) in mice. METHODS: (64)Cu-Labeled 800- or 525-nm emission wavelength QD (21- or 12-nm diameter), with or without 2,000 MW (molecular weight) polyethylene glycol (PEG), were injected intravenously into mice (5.55 MBq/25 pmol QD) and studied using well counting or by serial microPET and region-of-interest analysis. RESULTS: Both methods show rapid uptake by the liver (27.4-38.9 %ID/g) (%ID/g is percentage injected dose per gram tissue) and spleen (8.0-12.4 %ID/g). Size has no influence on biodistribution within the range tested here. Pegylated QD have slightly slower uptake into liver and spleen (6 vs. 2 min) and show additional low-level bone uptake (6.5-6.9 %ID/g). No evidence of clearance from these organs was observed. CONCLUSION: Rapid reticuloendothelial system clearance of QD will require modification of QD for optimal utility in imaging living subjects. Formal quantitative biodistribution/imaging studies will be helpful in studying many types of nanoparticles, including quantum dots.


Assuntos
Compostos de Cádmio/farmacocinética , Radioisótopos de Cobre , Pontos Quânticos , Compostos de Selênio/farmacocinética , Animais , Osso e Ossos/metabolismo , Compostos de Cádmio/química , Fígado/metabolismo , Camundongos , Camundongos Nus , Polietilenoglicóis/química , Tomografia por Emissão de Pósitrons/métodos , Compostos de Selênio/química , Baço/metabolismo , Distribuição Tecidual , Compostos de Zinco/química , Compostos de Zinco/farmacocinética
4.
IEEE Trans Nanobioscience ; 5(4): 231-8, 2006 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-17181021

RESUMO

Quantum dots (QDOTs) have been widely recognized by the scientific community and the biotechnology industry, as witnessed by the exponential growth of this field in the past several years. We describe the synthesis and characterization of visible and near infrared QDots--a critical step for engineering organic molecules like proteins and peptides for building nanocomposite materials with multifunctional properties suitable for biological applications.


Assuntos
Materiais Revestidos Biocompatíveis/química , Técnicas de Sonda Molecular , Peptídeos/química , Peptídeos/metabolismo , Pontos Quânticos , Espectrofotometria Infravermelho/métodos , Teste de Materiais
5.
ACS Nano ; 4(12): 7229-40, 2010 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-21121616

RESUMO

Vaults are naturally occurring ribonucleoprotein particles with an enormous interior volume, large enough to encapsulate hundreds of proteins. They are highly conserved and are present in nearly all eukaryotic cells ranging from 10(4) to 10(7) particles per cell. Recombinant vaults can be produced in vitro and engineered to allow cell targeting and protein packaging. These nanometer-sized particles have many desirable characteristics that may give them advantages for use as drug delivery vehicles. Using photoactivatable green fluorescent protein (PAGFP) labeled vaults, we demonstrate that the particles rapidly diffuse throughout the cytoplasm following single pixel photoactivation in live cells. Their in vivo movement remained relatively unchanged despite exposure to a variety of cellular stresses, suggesting that vaults are largely unconstrained in the cytoplasm. Fluorescence resonance energy transfer (FRET) was observed from polyethylene glycol (PEG) fused hybrid cells that expressed either CFP or YFP labeled vaults, indicating that vaults can exchange major vault protein (MVP) subunits in vivo. Investigation into the mechanism of this exchange in vitro using recombinant vaults demonstrated that they were capable of rapidly separating at the particle waist and reassembling back into whole vaults, supporting a half vault exchange mechanism. This data suggests a means whereby vaults can functionally interact with their cellular environment and deliver materials packaged within their interior.


Assuntos
Citoplasma/metabolismo , Nanopartículas , Partículas de Ribonucleoproteínas em Forma de Abóbada/química , Partículas de Ribonucleoproteínas em Forma de Abóbada/metabolismo , Animais , Linhagem Celular Tumoral , Difusão , Transferência Ressonante de Energia de Fluorescência , Humanos , Microscopia Eletrônica de Transmissão , Modelos Moleculares , Polietilenoglicóis/química , Conformação Proteica , Transporte Proteico , Espalhamento a Baixo Ângulo , Difração de Raios X
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA