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1.
Teach Learn Med ; : 1-27, 2024 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-38686837

RESUMO

PHENOMENON: Despite the importance of diet in the prevention and management of many common chronic diseases, nutrition training in medicine is largely inadequate in medical school and residency. The emerging field of culinary medicine offers an experiential nutrition learning approach with the potential to address the need for improved nutrition training of physicians. Exploring this innovative nutrition training strategy, this scoping review describes the nature of culinary medicine experiences for medical students and resident physicians, their impact on the medical trainees, and barriers and facilitators to their implementation. APPROACH: This scoping review used the Joanna Briggs Institute methodology for scoping reviews and the Preferred Reporting Items for Systematic Reviews and Meta-analyses extension for Scoping Reviews (PRISMA-ScR) checklist as guides. Eligible publications described the nature, impact, facilitators, and/or barriers of nutrition and food preparation learning experiences for medical students and/or residents. Additional inclusion criteria were location (U.S. or Canada), allopathic or osteopathic, English, human subjects, and publication year (2002 or later). The search strategy included 4 electronic databases. Two reviewers independently screened titles/abstracts and a third reviewer resolved discrepancies. The full-text review consisted of 2 independent reviews with discrepancies resolved by a third reviewer or by consensus if needed, and the research team extracted data from the included articles based on the nature, impact, barriers, and facilitators of culinary medicine experiences for medical trainees. FINDINGS: The publication search resulted in 100 publications describing 116 experiences from 70 institutions. Thirty-seven publications described pilot experiences. Elective/extracurricular and medical student experiences were more common than required and resident experiences, respectively. Experiences varied in logistics, instruction, and curricula. Common themes of tailored culinary medicine experiences included community engagement/service-based learning, interprofessional education, attention to social determinants of health, trainee well-being, and cultural considerations. Program evaluations commonly reported the outcome of experiences on participant attitudes, knowledge, skills, confidence, and behaviors. Frequent barriers to implementation included time, faculty, cost/funding, kitchen space, and institutional support while common facilitators of experiences included funding/donations, collaboratives and partnerships, teaching kitchen access, faculty and institutional support, and trainee advocacy. INSIGHTS: Culinary medicine is an innovative approach to address the need and increased demand for improved nutrition training in medicine. The findings from this review can guide medical education stakeholders interested in developing or modifying culinary medicine experiences. Despite barriers to implementation, culinary medicine experiences can be offered in a variety of ways during undergraduate and graduate medical education and can be creatively designed to fulfill some accreditation standards.

2.
Med Sci Educ ; 33(3): 659-667, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-37501800

RESUMO

Purpose: This paper aims to characterize the use of demographic data in multiple-choice questions from a commercial preclinical question bank and determine if there is appropriate use of different distractors. Background: Multiple-choice questions for medical students often include vignettes describing a patient's presentation to help guide students to a diagnosis, but overall patterns of usage between different types of nonmedical patient information in question stems have yet to be determined. Methods: Three hundred eighty of 453 randomly selected questions were included for analysis after determining they contained a clinical vignette and required a diagnosis. The vignettes and following explanations were then examined for the presence/absence of 11 types of demographic information, including age, sex/gender, and socioeconomic status. We compared both the usage frequency and relevance between the 11 information types. Results: Most information types were present in less than 10% of clinical vignettes, but age and sex/gender were present in over 95% of question stems. Over 50% of questions included irrelevant information about age and sex/gender, but 75% of questions did not include any irrelevant information of other types. Patient weight and environmental exposures were significantly more likely to be relevant than age or sex/gender. Discussion: Students using the questions in this study will frequently gain practice incorporating age and sex/gender into their clinical reasoning while receiving little exposure to other demographic information. Based on our findings, we posit that questions could include more irrelevant information, outside age and sex/gender, to better approximate real clinical scenarios and ensure students do not overvalue certain demographic data. Supplementary Information: The online version contains supplementary material available at 10.1007/s40670-023-01778-z.

3.
Med Sci Educ ; 32(6): 1319-1321, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36193110

RESUMO

Even prior to the COVID pandemic, the push for medical schools to adopt virtual anatomy curricula in lieu of human cadaveric dissection was growing. In this study, musculoskeletal and gastrointestinal anatomy examination scores of first-year medical students at the UNC School of Medicine were compared across three consecutive years. These classes experienced in-person, virtual, and hybridized anatomy curriculum, respectively. There was not a single instance noted where in-person curriculum produced higher examination scores than virtual or hybridized models. By incorporating virtual or hybridized models of anatomy, medical education programs can effectively reach and educate students far beyond the traditional cadaver laboratory.

4.
BMC Med Educ ; 22(1): 585, 2022 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-35907953

RESUMO

BACKGROUND: The medical case vignette has long been used in medical student education and frequently includes demographic variables such as race, ethnicity and gender. However, inclusion of demographic variables without context may reinforce assumptions and biases. Yet, the absence of race, sexual orientation, and social determinants of health may reinforce a hidden curriculum that reflects cultural blindness. This replication study compared proportions of race, ethnicity, and gender with University of Minnesota (UMN) findings. This study sought to determine if there has been progress in the representation of demographic characteristics in case vignettes. METHODS: University of North Carolina (UNC) case vignettes from 2015-2016 were analyzed and compared to UMN case vignettes from 1996-1998. Data included mentions of race, ethnicity, gender and social determinants of health. RESULTS: In the 278 UNC vignettes, white race was noted in 19.7% of cases, black race was in 7.9% cases, and 76.6% of cases were unspecified. In the 983 UMN vignettes, white race was recorded in 2.85% cases, and black race in 0.41% cases. The institutions were significantly different in the proportion of their cases depicting race (0.20; 95% CI (0.15, 0.25)). Males were represented in the majority of vignettes. DISCUSSION: Comparing case vignettes results from two medical schools suggests that reporting explicit demographic diversity was not significantly different. The findings illustrate that sex was the demographic characteristic consistently described, where males were over-represented. Based on these findings, greater cultural diversity as it intersects with social determinants of health is needed in medical student education.


Assuntos
Etnicidade , Estudantes de Medicina , População Negra , Feminino , Humanos , Masculino , Faculdades de Medicina , População Branca
5.
J Med Educ Curric Dev ; 8: 23821205211010479, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33997287

RESUMO

BACKGROUND: There is an ongoing call for leadership development in academic health care and medical students desire more training in this area. Although many schools offer combined MD/MBA programs or leadership training in targeted areas, these programs do not often align with medical school leadership competencies and are limited in reaching a large number of students. METHODS: The Leadership Initiative (LI) was a program created by a partnership between a School of Medicine (SOM) and Business School with a learning model that emphasized the progression from principles to practice, and the competencies of self-awareness, communication, and collaboration/teamwork. Through offerings across a medical school curriculum, the LI introduced leadership principles and provided an opportunity to apply them in an interactive activity or simulation. We utilized the existing SOM evaluation platform to collect data on program outcomes that included satisfaction, fidelity to the learning model, and impact. RESULTS: From 2017 to 2020, over 70% of first-year medical students participated in LI course offerings while a smaller percentage of fourth-year students engaged in the curriculum. Most students had no prior awareness of LI course material and were equivocal about their ability to apply lessons learned to their medical school experience. Students reported that the LI offerings provided opportunities to practice the skills and competencies of self-awareness, communication, and collaboration/teamwork. DISCUSSION: Adding new activities to an already crowded medical curriculum was the greatest logistical challenge. The LI was successful in introducing leadership principles but faced obstacles in having participants apply and practice these principles. Most students reported that the LI offerings were aligned with the foundational competencies.

6.
BMC Med Educ ; 20(1): 423, 2020 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-33176776

RESUMO

BACKGROUND: Kolb's Cycle of Learning Theory acts as a foundational framework for the evolution of knowledge gained by learners throughout their education. Through Kolb's cycle of experiential learning, one's preferred way of learning could impact academic achievement in the pre-clinical years of medical education. METHODS: The medical student classes of 2020 and 2021 at a public university in the southeastern U.S. were invited to complete Kolb's Learning Style Inventory (LSI). For those participants completing the LSI, examination results for their pre-clinical blocks were obtained and matched to the LSI results. Examination scores (locally-developed examinations and customized National Board of Medical Examiners (NBME) final examinations) were compared by LSI classification for each examination using Kruskal-Wallis Test. RESULTS: Out of 360 possible participants, 314 (87.2%) completed the Learning Style Inventory. Convergers and Assimilators made up 84.1% [Convergers (n = 177, 56.4%), Assimilators (n = 87, 27.7%)]. Accommodators (n = 25, 7.9%) and Divergers (n = 25, 7.9%) made up the remaining sample. Accomodators' scores were significantly lower on locally-developed examinations in Principles of Medicine, Hematology, and Gastrointestinal System. The only NBME examination that demonstrated a significant difference across learning styles was from the Cardiovascular block. CONCLUSIONS: Upon reviewing Kolb's LSI, our study indicated that performance on the customized NBME examinations minimized the variance in performance compared to locally-developed examinations. The lack of variance across learning styles for all but one NBME final examination appears to provide a more equitable assessment strategy.


Assuntos
Educação Médica , Estudantes de Medicina , Cognição , Humanos , Aprendizagem , Aprendizagem Baseada em Problemas
7.
PLoS One ; 15(11): e0241631, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33180800

RESUMO

The unique cellular organization and transparent function of the ocular lens depend on the continuous differentiation of immature epithelial cells on the lens anterior surface into mature elongated fiber cells within the lens core. A ubiquitous event during lens differentiation is the complete elimination of organelles required for mature lens fiber cell structure and transparency. Distinct pathways have been identified to mediate the elimination of non-nuclear organelles and nuclei. Recently, we reported the discovery of a unique structure in developing fiber cells of the chick embryo lens, called the Nuclear Excisosome, that is intractably associated with degrading nuclei during lens fiber cell differentiation. In the chick lens, the Nuclear Excisosome is derived from projections of adjacent cells contacting the nuclear envelope during nuclear elimination. Here, we demonstrate that, in contrast to the avian model, Nuclear Excisosomes in a primate model, Galago (bush baby) monkeys, are derived through the recruitment of mitochondria to form unique linear assemblies that define a novel primate Nuclear Excisosome. Four lenses from three monkeys aged 2-5 years were fixed in formalin, followed by paraformaldehyde, then processed for Airyscan confocal microscopy or transmission electron microscopy. For confocal imaging, fluorescent dyes labelled membranes, carbohydrate in the extracellular space, filamentous actin and nuclei. Fiber cells from Galago lenses typically displayed prominent linear structures within the cytoplasm with a distinctive cross-section of four membranes and lengths up to 30 µm. The outer membranes of these linear structures were observed to attach to the outer nuclear envelope membrane to initiate degradation near the organelle-free zone. The origin of these unique structures was mitochondria in the equatorial epithelium (not from plasma membranes of adjacent cells as in the chick embryo model). Early changes in mitochondria appeared to be the collapse of the cristae and modification of one side of the mitochondrial outer membrane to promote accumulation of protein in a dense cluster. As a mitochondrion surrounded the dense protein cluster, an outer mitochondrial membrane enclosed the protein to form a core and another outer mitochondrial membrane formed the outermost layer. The paired membranes of irregular texture between the inner core membrane and the outer limiting membrane appeared to be derived from modified mitochondrial cristae. Several mitochondria were involved in the formation and maturation of these unique complexes that apparently migrated around the fulcrum into the cytoplasm of nascent fiber cells where they were stabilized until the nuclear degradation was initiated. Thus, unlike in the chick embryo, the Galago lenses degraded nuclear envelopes with a Nuclear Excisosome derived from multiple mitochondria in the epithelium that formed novel linear assemblies in developing fiber cells. These findings suggest that recruitment of distinct structures is required for Nuclear Excisosome formation in different species.


Assuntos
Núcleo Celular/ultraestrutura , Cristalino/ultraestrutura , Mitocôndrias/metabolismo , Actinas/metabolismo , Animais , Diferenciação Celular , Núcleo Celular/metabolismo , Espaço Extracelular/metabolismo , Galago , Cristalino/crescimento & desenvolvimento , Cristalino/metabolismo
8.
J Dent Educ ; 84(10): 1108-1116, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32585048

RESUMO

PURPOSE: The Association of American Medical Colleges and American Dental Education Association have identified oral health knowledge, skills, and attitudes shared by both medical and dental professionals. Although oral health was deemed an essential competency for medical practitioners, our state struggled to ensure learners received proper training. This training deficit resulted in conducting a needs assessment and implementing an oral health interprofessional module at our schools. METHODS: First-year medical students and clinical faculty were emailed surveys in 2016 to obtain baseline information. A team of faculty and students from the Schools of Medicine and Dentistry reviewed the curriculum to determine where to augment oral health content. An oral health module to teach a basic head, neck, and oral examination to first-year medical students during their patient-centered care small-group sessions was implemented and evaluated. RESULTS: Only 13.6% of faculty respondents were aware of national oral health competency recommendations, and <50% rated oral health important for primary care physicians (PCPs) to include in history, physical exam, or oral health counseling. On baseline, ≤25% of PCP respondents reported integrating the listed skills in their practice, and most indicated lacking expertise to teach oral health. Teaching sessions were rated helpful by students and faculty. After the teaching sessions, ratings on the importance of including oral health significantly increased from baseline. CONCLUSION: Collaboration between Schools of Dentistry and Medicine successfully integrated oral health into medical school curriculum and improved the tutors' attitudes of its importance.


Assuntos
Educação em Saúde Bucal , Estudantes de Medicina , Currículo , Humanos , Saúde Bucal , Faculdades de Medicina
9.
Med Sci Educ ; 30(1): 47-51, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34457635

RESUMO

There is insufficient evidence supporting complete dissection as essential for medical student education. Due to physical constraints, we employed a hybrid teaching method. Gross anatomy practical examinations from two medical student classes were analyzed to determine performance on dissected versus student-prosected material. Overall, student performance on questions pertaining to personally dissected material was similar to performance on questions learned by studying student-prosected material. We found dissection time can be reduced without impacting medical student examination performance.

10.
Med Sci Educ ; 30(3): 1035-1042, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34457765

RESUMO

BACKGROUND: Applying active recall during studying vexes medical students. The integration of social media into medical education is rapidly expanding; however, there is minimal use of Instagram in medical education. Histology is a visually dominant subject and pairs well with Instagram. We sought to create a standardized process for medical educators to establish Instagram as a study tool for histology. METHODS: An Instagram account accessible to MS1s was created. Histology images in the course syllabus along with questions and explanations for each image were organized and posted to Instagram in a question and answer format. Instagram analytics on student engagement were gathered along with student survey responses. RESULTS: Seventy-four percent (141/190) of the class followed the account. Images had an average of 442 total views. Images had an average of 3.5 views per user (VPUs), ranging from 2.6 to 4.3 VPUs, suggesting that students are viewing images multiple times. Ninety-eight percent of survey responders found the account easy to use. Ninety-five percent said studying the account increased their confidence when answering histology questions on exams, and 75% said the account led to decreased stress when studying histology. DISCUSSION: Instagram is a platform that the majority of our medical students are already using daily. There was strong evidence of student engagement via Instagram analytics. Once a database of images with questions and answers is established, content can readily be posted to Instagram for students to study. Once established, this process can be applied to other visual content, such as anatomy, radiology, pathology, and microbiology.

11.
Acad Med ; 95(9S A Snapshot of Medical Student Education in the United States and Canada: Reports From 145 Schools): S383-S386, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33626726
12.
Med Sci Educ ; 29(1): 19-20, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34457442

RESUMO

Schools of medicine and dentistry on the same geographical campus have an opportunity to promote oral health by training physicians to become more skilled in screening for oral disease in addition to counseling and referring patients to dental health professionals.

13.
Med Sci Educ ; 29(3): 619-623, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34457523

RESUMO

BACKGROUND: There has been an emphasis on the implementation of self-directed learning in medical education. Kolb's experiential learning theory could be a useful framework in curriculum development. ACTIVITY: During the 2016-2017 academic year, participants completed the learning styles inventory. Percent time dedicated to lecture, laboratory, small groups, modules, simulations, and exams was collected along with participant academic performance. RESULTS: Findings showed that the curriculum delivery accommodated Assimilators and Convergers, with Convergers primarily outscoring the other categories. DISCUSSION: Although efforts emphasized self-directed learning, the curriculum is still delivered by lectures. Based on Kolb's theory, lecturing benefits Converger and Assimilator learning styles.

15.
PLoS One ; 11(8): e0160785, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27536868

RESUMO

An unresolved issue in structural biology is how the encapsulated lens removes membranous organelles to carry out its role as a transparent optical element. In this ultrastructural study, we establish a mechanism for nuclear elimination in the developing chick lens during the formation of the organelle-free zone. Day 12-15 chick embryo lenses were examined by high-resolution confocal light microscopy and thin section transmission electron microscopy (TEM) following fixation in 10% formalin and 4% paraformaldehyde, and then processing for confocal or TEM as described previously. Examination of developing fiber cells revealed normal nuclei with dispersed chromatin and clear nucleoli typical of cells in active ribosome production to support protein synthesis. Early signs of nuclear degradation were observed about 300 µm from the lens capsule in Day 15 lenses where the nuclei display irregular nuclear stain and prominent indentations that sometimes contained a previously undescribed macromolecular aggregate attached to the nuclear envelope. We have termed this novel structure the nuclear excisosome. This complex by confocal is closely adherent to the nuclear envelope and by TEM appears to degrade the outer leaflet of the nuclear envelope, then the inner leaflet up to 500 µm depth. The images suggest that the nuclear excisosome separates nuclear membrane proteins from lipids, which then form multilamellar assemblies that stain intensely in confocal and in TEM have 5 nm spacing consistent with pure lipid bilayers. The denuded nucleoplasm then degrades by condensation and loss of structure in the range 600 to 700 µm depth producing pyknotic nuclear remnants. None of these stages display any classic autophagic vesicles or lysosomes associated with nuclei. Uniquely, the origin of the nuclear excisosome is from filopodial-like projections of adjacent lens fiber cells that initially contact, and then appear to fuse with the outer nuclear membrane. These filopodial-like projections appear to be initiated with a clathrin-like coat and driven by an internal actin network. In summary, a specialized cellular organelle, the nuclear excisosome, generated in part by adjacent fiber cells degrades nuclei during fiber cell differentiation and maturation.


Assuntos
Núcleo Celular/ultraestrutura , Cristalino/citologia , Cristalino/embriologia , Animais , Autofagia , Diferenciação Celular , Embrião de Galinha , Cápsula do Cristalino/citologia , Cápsula do Cristalino/embriologia , Membrana Nuclear/ultraestrutura
16.
Anat Sci Educ ; 7(6): 450-60, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24431324

RESUMO

Any examination that involves moderate to high stakes implications for examinees should be psychometrically sound and legally defensible. Currently, there are two broad and competing families of test theories that are used to score examination data. The majority of instructors outside the high-stakes testing arena rely on classical test theory (CTT) methods. However, advances in item response theory software have made the application of these techniques much more accessible to classroom instructors. The purpose of this research is to analyze a common medical school anatomy examination using both the traditional CTT scoring method and a Rasch measurement scoring method to determine which technique provides more robust findings, and which set of psychometric indicators will be more meaningful and useful for anatomists looking to improve the psychometric quality and functioning of their examinations. Results produced by the more robust and meaningful methodology will undergo a rigorous psychometric validation process to evaluate construct validity. Implications of these techniques and additional possibilities for advanced applications are also discussed.


Assuntos
Anatomia/educação , Avaliação Educacional/métodos , Psicometria
17.
Mol Vis ; 19: 2352-9, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24319329

RESUMO

PURPOSE: Increased use of phacoemulsification procedures for cataract surgeries has resulted in a dramatic decrease in the availability of cataractous nuclear specimens for basic research into the mechanism of human cataract formation. To overcome such difficulties, a fixation protocol was developed to provide good initial fixation of human donor lenses and extracted nuclei, when available, and is suitable for storing or shipping cataracts to laboratories where structural studies could be completed. METHODS: Cataractous lens nuclei (n=19, ages 12 to 74 years) were obtained from operating suites after extracapsular extraction. Transparent human donor lenses (n=27, ages 22 to 92 years) were obtained from the Ramayamma International Eye Bank. After the dimensions were measured with a digital caliper, samples were preserved in 10% formalin (neutral buffered) for 24 h and followed by fixation in 4% paraformaldehyde (pH 7.2) for 48 h. Samples were stored cold (4 °C) in buffer until shipped. Samples were photographed and measured before further processing for transmission electron microscopy. RESULTS: The dimensions of the samples varied slightly after short fixation followed by 1 to 5 months' storage before transmission electron microscopy processing. The mean change in the axial thickness of the donor lenses was 0.15±0.21 mm or 3.0±5.4%, while that of the extracted nuclei was 0.05±0.24 mm or 1.8±7.6%. Because the initial concern was whether the nuclear core was preserved, thin sections were examined from the embryonic and fetal nuclear regions. All cellular structures were preserved, including the cytoplasm, complex edge processes, membranes, and junctions. The preservation quality was excellent and nearly equivalent to preservation of fresh lenses even for the lens cortex. Cell damage characteristic of specific nuclear cataract types was easily recognized. CONCLUSIONS: The novel fixation protocol appears effective in preserving whole donor lenses and cataractous nuclei over a wide age range. Dimensions varied only 2%-3%, and fiber cell damage correlated well with standard fixation. These methods enable researchers and clinicians in remote settings to preserve donor lenses and rare examples of extracapsular extractions for detailed examination at later times.


Assuntos
Extração de Catarata , Córtex do Cristalino/ultraestrutura , Núcleo do Cristalino/ultraestrutura , Manejo de Espécimes/métodos , Fixação de Tecidos/métodos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Catarata/patologia , Criança , Bancos de Olhos , Feminino , Fixadores , Formaldeído , Humanos , Córtex do Cristalino/patologia , Córtex do Cristalino/cirurgia , Núcleo do Cristalino/patologia , Núcleo do Cristalino/cirurgia , Masculino , Microscopia Eletrônica de Transmissão , Microtomia , Pessoa de Meia-Idade , Facoemulsificação , Polímeros , Manejo de Espécimes/normas , Fixação de Tecidos/normas
18.
Exp Eye Res ; 116: 411-8, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24183661

RESUMO

The purpose is to determine the nature of the cellular rearrangements occurring through the remodeling zone (RZ) in human donor lenses, identified previously by confocal microscopy to be about 100 µm from the capsule. Human donor lenses were fixed with 10% formalin followed by 4% paraformaldehyde prior to processing for transmission electron microscopy. Of 27 fixed lenses, ages 22, 55 and 92 years were examined in detail. Overview electron micrographs confirmed the loss of cellular organization present in the outer cortex (80 µm thick) as the cells transitioned into the RZ. The transition occurred within a few cell layers and fiber cells in the RZ completely lost their classical hexagonal cross-sectional appearance. Cell interfaces became unusually interdigitated and irregular even though the radial cell columns were retained. Gap junctions appeared to be unaffected. After the RZ (40 µm thick), the cells were still irregular but more recognizable as fiber cells with typical interdigitations and the appearance of undulating membranes. Cell thickness was irregular after the RZ with some cells compacted, while others were not, up to the zone of full compaction in the adult nucleus. Similar dramatic cellular changes were observed within the RZ for each lens regardless of age. Because the cytoskeleton controls cell shape, dramatic cellular rearrangements that occur in the RZ most likely are due to alterations in the associations of crystallins to the lens-specific cytoskeletal beaded intermediate filaments. It is also likely that cytoskeletal attachments to membranes are altered to allow undulating membranes to develop.


Assuntos
Cristalinas/metabolismo , Cristalino/ultraestrutura , Adulto , Idoso , Idoso de 80 Anos ou mais , Citoesqueleto/ultraestrutura , Junções Comunicantes/ultraestrutura , Humanos , Cristalino/metabolismo , Microscopia Eletrônica , Pessoa de Meia-Idade , Adulto Jovem
19.
Exp Eye Res ; 116: 141-50, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24012988

RESUMO

The eye lens consists of a layer of epithelial cells that overlay a series of differentiating fiber cells that upon maturation lose their mitochondria, nuclei and other organelles. Lens transparency relies on the metabolic function of mitochondria contained in the lens epithelial cells and in the immature fiber cells and the programmed degradation of mitochondria and other organelles occurring upon lens fiber cell maturation. Loss of lens mitochondrial function in the epithelium or failure to degrade mitochondria and other organelles in lens fiber cells results in lens cataract formation. To date, the mechanisms that govern the maintenance of mitochondria in the lens and the degradation of mitochondria during programmed lens fiber cell maturation have not been fully elucidated. Here, we demonstrate using electron microscopy and dual-label confocal imaging the presence of autophagic vesicles containing mitochondria in lens epithelial cells, immature lens fiber cells and during early stages of lens fiber cell differentiation. We also show that mitophagy is induced in primary lens epithelial cells upon serum starvation. These data provide evidence that autophagy occurs throughout the lens and that mitophagy functions in the lens to remove damaged mitochondria from the lens epithelium and to degrade mitochondria in the differentiating lens fiber cells for lens development. The results provide a novel mechanism for how mitochondria are maintained to preserve lens metabolic function and how mitochondria are degraded upon lens fiber cell maturation.


Assuntos
Autofagia , Catarata/patologia , Cristalino/ultraestrutura , Mitofagia , Organelas/ultraestrutura , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Catarata/metabolismo , Proliferação de Células , Embrião de Galinha , Humanos , Cristalino/metabolismo , Microscopia Eletrônica , Pessoa de Meia-Idade , Adulto Jovem
20.
Exp Eye Res ; 101: 72-81, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22728317

RESUMO

Human nuclear cataract formation is a multi-factorial disease with contributions to light scattering from many cellular sources that change their scattering properties over decades. The aging process produces aggregation of cytoplasmic crystallin proteins, which alters the protein packing and texture of the cytoplasm. Previous studies of the cytoplasmic texture quantified increases in density fluctuations in protein packing and theoretically predicted the corresponding scattering. Multilamellar bodies (MLBs) are large particles with a core of crystallin cytoplasm that have been suggested to be major sources of scattering in human nuclei. The core has been shown to condense over time such that the refractive index increases compared to the adjacent aged and textured cytoplasm. Electron tomography is used here to visualize the 3D arrangement of protein aggregates in aged and cataractous lens nuclear cytoplasm compared to the dense protein packing in the cores of MLBs. Thin sections, 70 nm thick, were prepared from epoxy-embedded human transparent donor lenses and nuclear cataracts. Tilt series were collected on an FEI T20 transmission electron microscope (TEM) operated at 200 kV using 15 nm gold particles as fiducial markers. Images were aligned and corrected with FEI software and reconstructed with IMOD and other software packages to produce animated tilt series and stereo anaglyphs. The 3D views of protein density showed the relatively uniform packing of proteins in aged transparent lens nuclear cytoplasm and less dense packing of aged cataractous cytoplasm where many low-density regions can be appreciated in the absence of the TEM projection artifacts. In contrast the cores of the MLBs showed a dense packing of protein with minimal density fluctuations. These observations support the conclusion that, during the nuclear cataract formation, alterations in protein packing are extensive and can result in pronounced density fluctuations. Aging causes the MLB cores to become increasingly different in their protein packing from the adjacent cytoplasm. These results support the hypothesis that the MLBs increase their scattering with age and nuclear cataract formation.


Assuntos
Envelhecimento/patologia , Catarata/patologia , Cristalinas/ultraestrutura , Tomografia com Microscopia Eletrônica , Corpos de Inclusão/ultraestrutura , Núcleo do Cristalino/ultraestrutura , Multimerização Proteica , Adulto , Idoso , Idoso de 80 Anos ou mais , Citoplasma , Humanos , Imageamento Tridimensional , Luz , Bicamadas Lipídicas , Pessoa de Meia-Idade , Espalhamento de Radiação
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