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1.
Cancer Treat Res ; 176: 195-224, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30596220

RESUMEN

There are a number of rare T-cell lymphoma subtypes that may be encountered in clinical practice. In recent years, improved immunohistochemical techniques and molecular tumor profiling have permitted refinement of some of the diagnostic categories in this group, as well as the recognition of distinct conditions not previously well elucidated. In this chapter, we cover the diagnostic and clinical features of some of the more common of these conditions, including subcutaneous panniculitis-like T-cell lymphoma, cutaneous gamma-delta T-cell lymphoma, enteropathy-associated T-cell lymphoma, monomorphic epitheliotropic intestinal T-cell lymphoma, primary cutaneous CD8-positive aggressive epidermotropic cytotoxic T-cell lymphoma, CD4-positive small/medium T-cell lymphoproliferative disorder, and acral CD8-positive T-cell lymphoma. Given the rarity of these conditions, optimal treatments approaches are not always well established, not least as data from large-scale clinical trials are lacking. In this chapter, we aim to provide a summation of current thinking around best treatment, as well as highlighting some controversies in the management of these diagnoses.


Asunto(s)
Linfoma Cutáneo de Células T , Linfoma de Células T , Paniculitis , Neoplasias Cutáneas , Humanos , Linfoma de Células T/diagnóstico , Linfoma de Células T/tratamiento farmacológico , Linfoma Cutáneo de Células T/diagnóstico , Linfoma Cutáneo de Células T/tratamiento farmacológico , Linfocitos T
2.
Bioorg Med Chem ; 27(24): 115157, 2019 12 15.
Artículo en Inglés | MEDLINE | ID: mdl-31727451

RESUMEN

N-Methylpyrrolidone is a solvent molecule which has been shown to compete with acetyl-lysine-containing peptides for binding to bromodomains. From crystallographic studies, it has also been shown to closely mimic the acetamide binding motif in several bromodomains, but has not yet been directly pursued as a fragment in bromodomain inhibition. In this paper, we report the elaboration of N-methylpyrrolidone as a potential lead in fragment-based drug design. Firstly, N-methylpyrrolidone was functionalised to provide points for chemical elaboration. Then, the moiety was incorporated into analogues of the reported bromodomain inhibitor, Olinone. X-ray crystallography revealed that the modified analogues showed comparable binding affinity and structural mimicry to Olinone in the bromodomain binding site.


Asunto(s)
Proteínas de Ciclo Celular/química , Diseño de Fármacos , Pirrolidinonas/síntesis química , Factores de Transcripción/química , Sitios de Unión , Proteínas de Ciclo Celular/metabolismo , Cristalografía por Rayos X , Transferencia Resonante de Energía de Fluorescencia , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Modelos Moleculares , Estructura Molecular , Unión Proteica , Conformación Proteica , Pirrolidinonas/química , Relación Estructura-Actividad , Factores de Transcripción/metabolismo
3.
J Evol Biol ; 29(2): 265-76, 2016 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-26492510

RESUMEN

Despite growing evidence for nongenetic inheritance, the ecological conditions that favour the evolution of heritable parental or grandparental effects remain poorly understood. Here, we systematically explore the evolution of parental effects in a patch-structured population with locally changing environments. When selection favours the production of a mix of offspring types, this mix differs according to the parental phenotype, implying that parental effects are favoured over selection for bet-hedging in which the mixture of offspring phenotypes produced does not depend on the parental phenotype. Positive parental effects (generating a positive correlation between parental and offspring phenotype) are favoured in relatively stable habitats and when different types of local environment are roughly equally abundant, and can give rise to long-term parental inheritance of phenotypes. By contrast, unstable habitats can favour negative parental effects (generating a negative correlation between parental and offspring phenotype), and under these circumstances, even slight asymmetries in the abundance of local environmental states select for marked asymmetries in transmission fidelity.


Asunto(s)
Evolución Biológica , Modelos Biológicos , Fenotipo , Adaptación Fisiológica , Distribución Animal , Animales , Ambiente , Aptitud Genética , Selección Genética
4.
Nature ; 454(7207): 968-70, 2008 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-18719583

RESUMEN

The giant elliptical galaxy NGC 1275, at the centre of the Perseus cluster, is surrounded by a well-known giant nebulosity of emission-line filaments, which are plausibly in excess of 10(8) years old. The filaments are dragged out from the centre of the galaxy by radio-emitting 'bubbles' rising buoyantly in the hot intracluster gas, before later falling back. They act as markers of the feedback process by which energy is transferred from the central massive black hole to the surrounding gas. The mechanism by which the filaments are stabilized against tidal shear and dissipation into the surrounding extremely hot (4 x 10(7) K) gas has been unclear. Here we report observations that resolve thread-like structures in the filaments. Some threads extend over 6 kpc, yet are only 70 pc wide. We conclude that magnetic fields in the threads, in pressure balance with the surrounding gas, stabilize the filaments, so allowing a large mass of cold gas to accumulate and delay star formation.

5.
Nat Commun ; 15(1): 6583, 2024 Aug 03.
Artículo en Inglés | MEDLINE | ID: mdl-39097569

RESUMEN

A major goal in evolutionary biology is to elucidate common principles that drive human and other animal societies to adopt either a warlike or peaceful nature. One proposed explanation for the variation in aggression between human societies is the democratic peace hypothesis. According to this theory, autocracies are more warlike than democracies because autocratic leaders can pursue fights for private gain. However, autocratic and democratic decision-making processes are not unique to humans and are widely observed across a diverse range of non-human animal societies. We use evolutionary game theory to evaluate whether the logic of democratic peace may apply across taxa; specifically adapting the classic Hawk-Dove model to consider conflict decisions made by groups rather than individuals. We find support for the democratic peace hypothesis without mechanisms involving complex human institutions and discuss how these findings might be relevant to non-human animal societies. We suggest that the degree to which collective decisions are shared may explain variation in the intensity of intergroup conflict in nature.


Asunto(s)
Evolución Biológica , Teoría del Juego , Animales , Humanos , Democracia , Agresión , Conducta Animal , Toma de Decisiones , Conflicto Psicológico
6.
J Evol Biol ; 26(7): 1488-98, 2013 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-23675944

RESUMEN

Models of parental investment typically assume that populations are well mixed and homogeneous and have devoted little attention to the impact of spatial variation in the local environment. Here, in a patch-structured model with limited dispersal, we assess to what extent resource-rich and resource-poor mothers should alter the size of their young in response to the local environment in their patch. We show that limited dispersal leads to a correlation between maternal and offspring environments, which favours plastic adjustment of offspring size in response to local survival risk. Strikingly, however, resource-poor mothers are predicted to respond more strongly to local survival risk, whereas resource-rich mothers are predicted to respond less strongly. This lack of sensitivity on the part of resource-rich mothers is favoured because they accrue much of their fitness through dispersing young. By contrast, resource-poor mothers accrue a larger fraction of their fitness through philopatric young and should therefore respond more strongly to local risk. Mothers with more resources gain a larger share of their fitness through dispersing young partly because their fitness in the local patch is constrained by the limited number of local breeding spots. In addition, when resource variation occurs at the patch level, the philopatric offspring of resource-rich mothers face stronger competition from the offspring of other local mothers, who also enjoy abundant resources. The effect of limited local breeding opportunities becomes less pronounced as patch size increases, but the impact of patch-level variation in resources holds up even with many breeders per patch.


Asunto(s)
Modelos Teóricos , Reproducción/fisiología , Adaptación Psicológica , Animales , Ambiente , Femenino , Masculino , Modelos Biológicos , Dinámica Poblacional
7.
S Afr J Sports Med ; 34(1): v34i1a13145, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-36815927

RESUMEN

Inclusion body myositis (IBM) is an inflammatory and degenerative autoimmune disease that targets specific muscle groups, causing severe muscle weakness. Exercise training is often contraindicated in myopathies as it may aggravate muscle damage and inflammation. Although some reported positive outcomes in muscle strength of early diagnosed IBM patients undergoing resistance training, there remains uncertainty as to whether exercise could be beneficial and safe in advanced stage IBM. Thus the aims of this research were to evaluate the safety and response of 16-weeks supervised resistance training on the health and muscle performance of an elderly participant diagnosed with advanced stage IBM. It was shown that the training had no adverse effects on the health of the patient. Muscle strength measured at eight weeks and on completion of the intervention, remained the same as at baseline. In conclusion, the exercise programme was found to be safe and seemed to maintain muscle strength in a patient with advanced stage IBM.

8.
Philos Trans R Soc Lond B Biol Sci ; 377(1851): 20210140, 2022 05 23.
Artículo en Inglés | MEDLINE | ID: mdl-35369752

RESUMEN

War, in human and animal societies, can be extremely costly but can also offer significant benefits to the victorious group. We might expect groups to go into battle when the potential benefits of victory (V) outweigh the costs of escalated conflict (C); however, V and C are unlikely to be distributed evenly in heterogeneous groups. For example, some leaders who make the decision to go to war may monopolize the benefits at little cost to themselves ('exploitative' leaders). By contrast, other leaders may willingly pay increased costs, above and beyond their share of V ('heroic' leaders). We investigated conflict initiation and conflict participation in an ecological model where single-leader-multiple-follower groups came into conflict over natural resources. We found that small group size, low migration rate and frequent interaction between groups increased intergroup competition and the evolution of 'exploitative' leadership, while converse patterns favoured increased intragroup competition and the emergence of 'heroic' leaders. We also found evidence of an alternative leader/follower 'shared effort' outcome. Parameters that favoured high contributing 'heroic' leaders, and low contributing followers, facilitated transitions to more peaceful outcomes. We outline and discuss the key testable predictions of our model for empiricists studying intergroup conflict in humans and animals. This article is part of the theme issue 'Intergroup conflict across taxa'.


Asunto(s)
Liderazgo , Animales
9.
Magn Reson Med ; 66(2): 564-73, 2011 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-21394767

RESUMEN

The aim of this study was to design a computer algorithm to assess the extent of cardiac edema from triple inversion recovery MR images of the human left ventricular myocardium. Twenty-one patients presenting with acute myocardial infarction were scanned within 48 h of the onset of symptoms. Eight patients were scanned a second time, 4 weeks after the initial event. Myocardial edema was detected in 27 of 29 studies using visual contour-based manual segmentation. A reference standard, created from the segmentations of three raters by voxel-wise majority voting, was compared to the edema mass estimates obtained using a newly developed computer algorithm. At baseline (n=20), the reference standard yielded an edema mass of 16.4±15.0 g (mean±SD) and the computer algorithm edema mass was 16.4±12.6 g. At follow-up (n=7), the reference standard edema mass was 7.1±4.4 g compared to 16.3±7.7 g at baseline. Computer algorithm estimates showed the same pattern of change with 5.7±5.7 g at follow-up compared to 20.8±13.8 g at baseline. Although there was a significant degree of discrepancy between reference standard and computer algorithm estimates of edema mass in individual patients, their overall agreement was good, with intraclass correlation coefficient ICC(3, 1)=0.753.


Asunto(s)
Algoritmos , Edema/diagnóstico , Edema/etiología , Interpretación de Imagen Asistida por Computador/métodos , Imagen por Resonancia Magnética/métodos , Infarto del Miocardio/complicaciones , Infarto del Miocardio/diagnóstico , Adulto , Anciano , Femenino , Humanos , Aumento de la Imagen/métodos , Masculino , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
10.
Nat Commun ; 12(1): 3717, 2021 06 23.
Artículo en Inglés | MEDLINE | ID: mdl-34162841

RESUMEN

Rawls argued that fairness in human societies can be achieved if decisions about the distribution of societal rewards are made from behind a veil of ignorance, which obscures the personal gains that result. Whether ignorance promotes fairness in animal societies, that is, the distribution of resources to reduce inequality, is unknown. Here we show experimentally that cooperatively breeding banded mongooses, acting from behind a veil of ignorance over kinship, allocate postnatal care in a way that reduces inequality among offspring, in the manner predicted by a Rawlsian model of cooperation. In this society synchronized reproduction leaves adults in a group ignorant of the individual parentage of their communal young. We provisioned half of the mothers in each mongoose group during pregnancy, leaving the other half as matched controls, thus increasing inequality among mothers and increasing the amount of variation in offspring birth weight in communal litters. After birth, fed mothers provided extra care to the offspring of unfed mothers, not their own young, which levelled up initial size inequalities among the offspring and equalized their survival to adulthood. Our findings suggest that a classic idea of moral philosophy also applies to the evolution of cooperation in biological systems.


Asunto(s)
Conducta Animal/fisiología , Herpestidae/fisiología , Reproducción/fisiología , Conducta Social , Animales , Animales Recién Nacidos , Peso Corporal/fisiología , Cruzamiento , Femenino , Masculino , Modelos Teóricos , Embarazo , Predominio Social
11.
J Exp Med ; 192(10): 1403-14, 2000 Nov 20.
Artículo en Inglés | MEDLINE | ID: mdl-11085743

RESUMEN

The essential upstream steps in granzyme B-mediated apoptosis remain undefined. Herein, we show that granzyme B triggers the mitochondrial apoptotic pathway through direct cleavage of Bid; however, cleavage of procaspases was stalled when mitochondrial disruption was blocked by Bcl-2. The sensitivity of granzyme B-resistant Bcl-2-overexpressing FDC-P1 cells was restored by coexpression of wild-type Bid, or Bid with a mutation of its caspase-8 cleavage site, and both types of Bid were cleaved. However, Bid with a mutated granzyme B cleavage site remained intact and did not restore apoptosis. Bid with a mutation preventing its interaction with Bcl-2 was cleaved but also failed to restore apoptosis. Rapid Bid cleavage by granzyme B (<2 min) was not delayed by Bcl-2 overexpression. These results clearly placed Bid cleavage upstream of mitochondrial Bcl-2. In granzyme B-treated Jurkat cells, endogenous Bid cleavage and loss of mitochondrial membrane depolarization occurred despite caspase inactivation with z-Val-Ala-Asp-fluoromethylketone or Asp-Glu-Val-Asp-fluoromethylketone. Initial partial processing of procaspase-3 and -8 was observed irrespective of Bcl-2 overexpression; however, later processing was completely abolished by Bcl-2. Overall, our results indicate that mitochondrial perturbation by Bid is necessary to achieve a lethal threshold of caspase activity and cell death due to granzyme B.


Asunto(s)
Apoptosis , Proteínas Portadoras/metabolismo , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Serina Endopeptidasas/metabolismo , Clorometilcetonas de Aminoácidos/farmacología , Animales , Proteína Proapoptótica que Interacciona Mediante Dominios BH3 , Células de la Médula Ósea , Proteínas Portadoras/genética , Caspasas/metabolismo , Células Cultivadas , Activación Enzimática , Granzimas , Humanos , Células Jurkat , Ratones , Mitocondrias/metabolismo , Modelos Biológicos , Procesamiento Proteico-Postraduccional , Proteínas Proto-Oncogénicas c-bcl-2/genética , Transducción de Señal , Receptor fas/metabolismo
12.
Analyst ; 135(7): 1606-17, 2010 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-20369214

RESUMEN

We demonstrate a new and extremely inexpensive, multipurpose desktop system for operating lab-on-a-chip (LOC) devices. The system provides all of the infrastructure necessary for genetic amplification and analysis, with orders of magnitude improvement in performance over our previous work. A modular design enables high levels of integration while allowing scalability to lower cost and smaller size. The component cost of this system is ca. $600, yet it could support many diagnostic applications. We demonstrate an implementation of genetic amplification via polymerase chain reaction (PCR), and analysis using capillary electrophoresis (CE). The PCR is able to amplify from single or several copies of target DNA and the CE performance (e.g. sensitivity) is comparable to that of commercial photomultiplier-based confocal lab-on-chip instrumentation. We believe this demonstrates that the cost of infrastructure need no longer be a barrier to the wide-spread application of LOC technologies in healthcare and beyond.


Asunto(s)
ADN/análisis , Dispositivos Laboratorio en un Chip , Técnicas Analíticas Microfluídicas/instrumentación , Técnicas Electroquímicas , Electroforesis Capilar/métodos , Técnicas Analíticas Microfluídicas/métodos , Reacción en Cadena de la Polimerasa/métodos
13.
J Int Med Res ; 38(4): 1213-24, 2010.
Artículo en Inglés | MEDLINE | ID: mdl-20925993

RESUMEN

Previous qualitative studies have revealed discrepancies between patients' and physicians' perceptions of rheumatoid arthritis (RA) and its treatment. Questionnaires were administered to 2795 patients with RA (756 from Europe; 2039 from the USA) to measure patients' perceptions regarding pain management in RA. Although the majority of patients reported their RA as somewhat-to-completely controlled, 75% of European and 82% of US patients reported their pain as moderate-to-severe in the previous 2 months. The majority of European (60%) and US (65%) patients reported dissatisfaction with their arthritis pain. Patients' pain levels corresponded with their disease severity. A higher percentage of patients who reported severe pain were being treated for depression than those who had moderate or mild pain. Patients in the USA rated pain relief as the top required benefit from their RA medication. A comprehensive examination of patients' perspectives regarding pain could lead to better patient care and pain management strategies.


Asunto(s)
Artritis Reumatoide/complicaciones , Artritis Reumatoide/terapia , Manejo del Dolor , Dolor/psicología , Pacientes/psicología , Adulto , Anciano , Demografía , Europa (Continente) , Fatiga/complicaciones , Femenino , Encuestas Epidemiológicas , Humanos , Masculino , Persona de Mediana Edad , Dolor/fisiopatología , Dimensión del Dolor , Satisfacción del Paciente , Encuestas y Cuestionarios , Estados Unidos
14.
Eur J Med Chem ; 191: 112120, 2020 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-32120339

RESUMEN

N-Methylpyrrolidone is one of several chemotypes that have been described as a mimetic of acetyl-lysine in the development of bromodomain inhibitors. In this paper, we describe the synthesis of a 4-phenyl substituted analogue - 1-methyl-4-phenylpyrrolidin-2-one - and the use of aryl substitution reactions as a divergent route for derivatives. Ultimately, this has led to structurally complex, chiral compounds with progressively improved affinity as inhibitors of bromodomain-containing protein 4.


Asunto(s)
Proteínas de Ciclo Celular/antagonistas & inhibidores , Diseño de Fármacos , Pirrolidinonas/farmacología , Factores de Transcripción/antagonistas & inhibidores , Proteínas de Ciclo Celular/metabolismo , Cristalografía por Rayos X , Relación Dosis-Respuesta a Droga , Transferencia Resonante de Energía de Fluorescencia , Humanos , Modelos Moleculares , Estructura Molecular , Pirrolidinonas/química , Relación Estructura-Actividad , Factores de Transcripción/metabolismo
15.
EJNMMI Phys ; 7(1): 24, 2020 May 05.
Artículo en Inglés | MEDLINE | ID: mdl-32372135

RESUMEN

BACKGROUND: Despite the advent of clinical PET-MR imaging for routine use in 2011 and the development of several methods to address the problem of attenuation correction, some challenges remain. We have identified and investigated several issues that might affect the reliability and accuracy of current attenuation correction methods when these are implemented for clinical and research studies of the brain. These are (1) the accuracy of converting CT Hounsfield units, obtained from an independently acquired CT scan, to 511 keV linear attenuation coefficients; (2) the effect of padding used in the MR head coil; (3) the presence of close-packed hair; (4) the effect of headphones. For each of these, we have examined the effect on reconstructed PET images and evaluated practical mitigating measures. RESULTS: Our major findings were (1) for both Siemens and GE PET-MR systems, CT data from either a Siemens or a GE PET-CT scanner may be used, provided the conversion to 511 keV µ-map is performed by the PET-MR vendor's own method, as implemented on their PET-CT scanner; (2) the effect of the head coil pads is minimal; (3) the effect of dense hair in the field of view is marked (> 10% error in reconstructed PET images); and (4) using headphones and not including them in the attenuation map causes significant errors in reconstructed PET images, but the risk of scanning without them may be acceptable following sound level measurements. CONCLUSIONS: It is important that the limitations of attenuation correction in PET-MR are considered when designing research and clinical PET-MR protocols in order to enable accurate quantification of brain PET scans. Whilst the effect of pads is not significant, dense hair, the use of headphones and the use of an independently acquired CT-scan can all lead to non-negligible effects on PET quantification. Although seemingly trivial, these effects add complications to setting up protocols for clinical and research PET-MR studies that do not occur with PET-CT. In the absence of more sophisticated PET-MR brain attenuation correction, the effect of all of the issues above can be minimised if the pragmatic approaches presented in this work are followed.

16.
EJNMMI Phys ; 7(1): 47, 2020 Jul 14.
Artículo en Inglés | MEDLINE | ID: mdl-32666231

RESUMEN

An amendment to this paper has been published and can be accessed via the original article.

17.
Cell Death Differ ; 15(4): 708-17, 2008 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-18202705

RESUMEN

Human GraB (hGraB) preferentially induces apoptosis via Bcl-2-regulated mitochondrial damage but can also directly cleave caspases and caspase substrates in cell-free systems. How hGraB kills cells when it is delivered by cytotoxic lymphocytes (CL) and the contribution of hGraB to CL-induced death is still not clear. We show that primary human natural killer (hNK) cells, which specifically used hGraB to induce target cell death, were able to induce apoptosis of cells whose mitochondria were protected by Bcl-2. Purified hGraB also induced apoptosis of Bcl-2-overexpressing targets but only when delivered at 5- to 10-fold the concentration required to kill cells expressing endogenous Bcl-2. Caspases were critical in this process as inhibition of caspase activity permitted clonogenic survival of Bcl-2-overexpressing cells treated with hGraB or hNK cells but did not protect cells that only expressed endogenous Bcl-2. Our data therefore show that hGraB triggers caspase activation via mitochondria-dependent and mitochondria-independent mechanisms that are activated in a hierarchical manner, and that the combined effects of Bcl-2 and direct caspase inhibition can block cell death induced by hGraB and primary hNK cells.


Asunto(s)
Apoptosis , Caspasas/metabolismo , Granzimas/metabolismo , Células Asesinas Naturales/enzimología , Mitocondrias/metabolismo , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Vesículas Secretoras/enzimología , Clorometilcetonas de Aminoácidos/farmacología , Apoptosis/efectos de los fármacos , Inhibidores de Caspasas , Técnicas de Cultivo de Célula , Células Cultivadas , Inhibidores de Cisteína Proteinasa/farmacología , Dipéptidos/farmacología , Activación Enzimática , Granzimas/antagonistas & inhibidores , Granzimas/genética , Células HeLa , Humanos , Células Asesinas Naturales/efectos de los fármacos , Mitocondrias/enzimología , Membranas Mitocondriales/metabolismo , Permeabilidad , Inhibidores de Proteasas/farmacología , Proteínas Proto-Oncogénicas c-bcl-2/genética , Vesículas Secretoras/efectos de los fármacos , Factores de Tiempo , Transfección , Proteína Inhibidora de la Apoptosis Ligada a X/metabolismo
18.
J Evol Biol ; 22(12): 2387-94, 2009 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19874439

RESUMEN

The handicap theory of sexual selection suggests that females prefer mates who display extravagant ornaments that advertise their quality or condition. It is often assumed that as such ornamental traits undergo sexually-selected exaggeration, they must inevitably become more sensitive to condition, and thus more informative. Here, we show that this is not necessarily the case. Depending on the precise form of the relationship between trait size and cost, expression may become more or less condition-dependent as the trait undergoes exaggeration, or may remain unchanged. This leads us to question how much of the information content of sexual signals can be attributed to sexual selection, and how much to pre-existing, naturally-selected condition-dependence.


Asunto(s)
Modelos Biológicos , Caracteres Sexuales , Conducta Sexual Animal , Animales , Ecosistema , Femenino , Masculino , Selección Genética
19.
J Cell Biol ; 101(3): 942-8, 1985 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-2993317

RESUMEN

Using ferritin-labeled protein A and colloidal gold-labeled anti-rabbit IgG, the fate of the sheep transferrin receptor has been followed microscopically during reticulocyte maturation in vitro. After a few minutes of incubation at 37 degrees C, the receptor is found on the cell surface or in simple vesicles of 100-200 nm, in which the receptor appears to line the limiting membrane of the vesicles. With time (60 min or longer), large multivesicular elements (MVEs) appear whose diameter may reach 1-1.5 micron. Inside these large MVEs are round bodies of approximately 50-nm diam that bear the receptor at their external surfaces. The limiting membrane of the large MVEs is relatively free from receptor. When the large MVEs fuse with the plasma membrane, their contents, the 50-nm bodies, are released into the medium. The 50-nm bodies appear to arise by budding from the limiting membrane of the intracellular vesicles. Removal of surface receptor with pronase does not prevent exocytosis of internalized receptor. It is proposed that the exocytosis of the approximately 50-nm bodies represents the mechanism by which the transferrin receptor is shed during reticulocyte maturation.


Asunto(s)
Receptores de Superficie Celular/metabolismo , Reticulocitos/metabolismo , Transferrina/metabolismo , Animales , Diferenciación Celular , Gránulos Citoplasmáticos/metabolismo , Exocitosis , Membranas Intracelulares/metabolismo , Microscopía Electrónica , Receptores de Transferrina , Reticulocitos/ultraestructura , Ovinos , Factores de Tiempo
20.
Trends Biochem Sci ; 25(1): 1-6, 2000 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-10637601

RESUMEN

Multidrug resistance mediated by the drug-efflux protein P-glycoprotein (P-gp) is one mechanism that tumor cells use to escape death induced by chemotherapeutic drugs. Although it is irrefutable that P-gp can efflux xenobiotics out of cells, biological regulatory functions for P-gp in multicellular organisms have yet to be established firmly. Recent observations have challenged the notion that P-gp has evolved merely to efflux xenotoxins out of healthy cells and raised the possibility that P-gp and related transporter molecules might play a fundamental role in regulating cell differentiation, proliferation and survival.


Asunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/fisiología , Muerte Celular/fisiología , Diferenciación Celular/fisiología , Animales , Transporte Biológico , Colesterol/metabolismo , Resistencia a Múltiples Medicamentos/fisiología , Humanos , Metabolismo de los Lípidos
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