RESUMO
UNLABELLED: In the classical form of α1-antitrypsin deficiency (ATD), aberrant intracellular accumulation of misfolded mutant α1-antitrypsin Z (ATZ) in hepatocytes causes hepatic damage by a gain-of-function, "proteotoxic" mechanism. Whereas some ATD patients develop severe liver disease (SLD) that necessitates liver transplantation, others with the same genetic defect completely escape this clinical phenotype. We investigated whether induced pluripotent stem cells (iPSCs) from ATD individuals with or without SLD could model these personalized variations in hepatic disease phenotypes. Patient-specific iPSCs were generated from ATD patients and a control and differentiated into hepatocyte-like cells (iHeps) having many characteristics of hepatocytes. Pulse-chase and endoglycosidase H analysis demonstrate that the iHeps recapitulate the abnormal accumulation and processing of the ATZ molecule, compared to the wild-type AT molecule. Measurements of the fate of intracellular ATZ show a marked delay in the rate of ATZ degradation in iHeps from SLD patients, compared to those from no liver disease patients. Transmission electron microscopy showed dilated rough endoplasmic reticulum in iHeps from all individuals with ATD, not in controls, but globular inclusions that are partially covered with ribosomes were observed only in iHeps from individuals with SLD. CONCLUSION: iHeps model the individual disease phenotypes of ATD patients with more rapid degradation of misfolded ATZ and lack of globular inclusions in cells from patients who have escaped liver disease. The results support the concept that "proteostasis" mechanisms, such as intracellular degradation pathways, play a role in observed variations in clinical phenotype and show that iPSCs can potentially be used to facilitate predictions of disease susceptibility for more precise and timely application of therapeutic strategies.
Assuntos
Células-Tronco Pluripotentes Induzidas/metabolismo , Hepatopatias/etiologia , Deficiência de alfa 1-Antitripsina/complicações , Células Cultivadas , Retículo Endoplasmático Rugoso/metabolismo , Humanos , Hepatopatias/metabolismo , alfa 1-Antitripsina/metabolismoRESUMO
Tapetum, orbicule, and pollen grain ontogeny in Colletia paradoxa and Discaria americana were studied with transmission electron microscopy (TEM). The ultrastructural changes observed during the different stages of development in the tapetal cells and related to orbicule and pollen grain formation are described. The proorbicules have the appearance of lipid globule, and their formation is related to the endoplasmic reticulum of rough type (ERr). This is the first report on the presence of orbicules in the family Rhamnaceae. Pollen grains are shed at the bicellular stage.
Assuntos
Pólen/fisiologia , Rhamnaceae/metabolismo , Citoplasma/metabolismo , Grão Comestível/metabolismo , Retículo Endoplasmático Rugoso/metabolismo , Gelatina/química , Glicerol/química , Lipídeos/química , Microscopia Eletrônica de Transmissão/métodos , Fenômenos Fisiológicos Vegetais , Pólen/química , Especificidade da EspécieRESUMO
Vesicle-based trafficking of hepatocellular transporters involves delivery of the newly-synthesized carriers from the rough endoplasmic reticulum to either the plasma membrane domain or to an endosomal, submembrane compartment, followed by exocytic targeting to the plasma membrane. Once delivered to the plasma membrane, the transporters usually undergo recycling between the plasma membrane and the endosomal compartment, which usually serves as a reservoir of pre-existing transporters available on demand. The balance between exocytic targeting and endocytic internalization from/to this recycling compartment is therefore a chief determinant of the overall capability of the liver epithelium to secrete bile and to detoxify endo and xenobiotics. Hence, it is a highly regulated process. Impaired regulation of this balance may lead to abnormal localization of these transporters, which results in bile secretory failure due to endocytic internalization of key transporters involved in bile formation. This occurs in several experimental models of hepatocellular cholestasis, and in most human cholestatic liver diseases. This review describes the molecular bases involved in the biology of the dynamic localization of hepatocellular transporters and its regulation, with a focus on the involvement of signaling pathways in this process. Their alterations in different experimental models of cholestasis and in human cholestatic liver disease are reviewed. In addition, the causes explaining the pathological condition (e.g. disorganization of actin or actin-transporter linkers) and the mediators involved (e.g. activation of cholestatic signaling transduction pathways) are also discussed. Finally, several experimental therapeutic approaches based upon the administration of compounds known to stimulate exocytic insertion of canalicular transporters (e.g. cAMP, tauroursodeoxycholate) are described.
Assuntos
Colestase/metabolismo , Fígado/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Animais , Bile/metabolismo , Membrana Celular/metabolismo , Colagogos e Coleréticos/uso terapêutico , Colestase/tratamento farmacológico , Modelos Animais de Doenças , Endocitose , Retículo Endoplasmático Rugoso/metabolismo , Endossomos/metabolismo , Exocitose , Humanos , Fígado/efeitos dos fármacos , Proteínas de Membrana Transportadoras/efeitos dos fármacos , Transporte Proteico , Transdução de Sinais , Xenobióticos/metabolismoRESUMO
Seasonal variations in the morphology of the parenchymal mass and function of the albumen gland/capsule gland complex have been studied in Pomacea canaliculata, together with the cellular types involved in the synthesis and secretion of perivitellin fluid components. The two major parenchymal cell types, albumen secretory cells (AS) and labyrinthic cells (LC), undergo seasonal variations throughout the annual reproductive cycle, which is divided into three periods. Both cellular types show maximal development and structural complexity during the reproductive period (spring and summer). AS cells have a well-developed Golgi complex and rough endoplasmic reticulum and their secretory granules show electron-dense particles of about 20 nm (probably galactogen). These cells are uniquely involved in ovorubin and PV2 perivitellin synthesis and their secretory granules are the single storage site for these two major perivitellins, as revealed by immunoelectron microscopy. AS also possess calcium deposits that infiltrate the cytoplasmic matrix. The luminal surfaces of LC exhibit long cilia intermingled with sparce short microvilli. Basally, the plasma membrane shows deep irregular folds that extend through the cytoplasm up to the subapical region. Calcium deposits infiltrate the cytoplasm and accumulate in the extracellular space of the basal labyrinth. Nerve terminals seem to be involved in the regulation of parenchymal cell secretion. At the post-reproductive period, AS markedly change their aspect following the release of most of the secretory granules into the acinar lumen. LC decrease in volume, the number of their cilia decreases, their cytoplasmic folds are much thinner and their extracellular spaces lack calcium particles. At the pre-reproductive period (winter), AS and LC recover and prepare for the subsequent period.
Assuntos
Gastrópodes/citologia , Vitelinas/biossíntese , Animais , Cálcio/fisiologia , Cílios/ultraestrutura , Proteínas do Ovo/biossíntese , Retículo Endoplasmático Rugoso/metabolismo , Retículo Endoplasmático Rugoso/ultraestrutura , Feminino , Gastrópodes/fisiologia , Complexo de Golgi/metabolismo , Complexo de Golgi/ultraestrutura , Imuno-Histoquímica , Microscopia Eletrônica de Transmissão , Oviductos/fisiologia , Oviductos/ultraestrutura , Reprodução/fisiologia , Estações do AnoRESUMO
The pituitary gonadotropins--luteinizing hormone and follicle-stimulating hormone--as well as the placental choriogonadotropin belong to the family of glycoprotein hormones. These structurally related hormones, which regulate several major reproductive functions of the body, are heterodimers consisting of a common alpha-subunit noncovalently bound to a beta-subunit. The N- and O-linked oligosaccharide chains of these gonadotropins play an important role in intracellular folding, assembly, secretion, metabolic clearance, and biological activity of the hormone. Gonadotropin glycosylation is a highly complex process; within the gonadotropes it is modulated by a variety of extrapituitary factors of hypothalamic and gonadal origin. In particular, estrogens and androgens appear to regulate terminal sialylation and/or sulfation of the oligosaccharide attachments and hence some functional properties of the gonadotropin molecule determined by these residues, i.e., metabolic clearance and in vivo biopotency. Through these extrapituitary inputs, the anterior pituitary may not only regulate the quantity but also the quality of the gonadotropin signal delivered to the gonads in a given physiologic or pathologic condition.
Assuntos
Hormônios Esteroides Gonadais/fisiologia , Gonadotropinas Hipofisárias/metabolismo , Processamento de Proteína Pós-Traducional/fisiologia , Motivos de Aminoácidos , Androgênios/farmacologia , Androgênios/fisiologia , Animais , Sequência de Carboidratos , Castração , Gonadotropina Coriônica/química , Gonadotropina Coriônica/metabolismo , Doenças do Sistema Endócrino/metabolismo , Retículo Endoplasmático Rugoso/metabolismo , Estrogênios/farmacologia , Estrogênios/fisiologia , Feminino , Hormônio Foliculoestimulante/química , Hormônio Foliculoestimulante/metabolismo , Glicosilação , Hormônios Esteroides Gonadais/farmacologia , Hormônio Liberador de Gonadotropina/fisiologia , Gonadotropinas Hipofisárias/química , Humanos , Sistema Hipotálamo-Hipofisário/fisiologia , Hormônio Luteinizante/química , Hormônio Luteinizante/metabolismo , Masculino , Mamíferos/fisiologia , Taxa de Depuração Metabólica , Dados de Sequência Molecular , Ácido N-Acetilneuramínico/metabolismo , Oligossacarídeos/metabolismo , Adeno-Hipófise/metabolismo , Placenta/metabolismo , Gravidez , Dobramento de Proteína , Ratos , Relação Estrutura-Atividade , Tireotropina/fisiologia , Hormônio Liberador de Tireotropina/fisiologiaRESUMO
The existence of functional lactotroph subpopulations was confirmed in primary pituitary cell cultures of female rats submitted to estrogen treatment and stimulation with thyrotrophin releasing hormone (TRH) and angiotensin II (A-II). In cell cultures of pituitary tissue, prolactin (PRL) producing cells represent about 50% of the total cell count, most of which (90%) correspond to a typical lactotroph subpopulation characterized by large secretory granules, 500-900 nm in diameter, and well developed rough endoplasmic reticulum (RER) and Golgi complex. Few atypical lactotrophs were detected with a quiescent appearance and containing smaller secretory granules, often indistinguishable from granular content of other pituitary cells. Depletion of endogenous estrogen caused by ovariectomy (OVX) decreased the pituitary lactotroph population about 34%, with a relative increase of atypical forms (56%). Replacement therapy with benzoate estradiol (EB) to OVX rats did not reverse the proportion of typical and atypical lactotrophs gauged in control pituitary glands. The predominant lactotroph population of OVX rat was an atypical PRL producing cell which displayed a quiescent appearance compatible with a reduced secretory activity. By contrast, estrogen administration to OVX rats caused a striking development of the RER, a hypertrophy of the Golgi complex and an increased storage of mature and immature secretory granules in the majority of lactotrophs. These features are compatible with a reactivated protein synthesis. Estrogen also enhanced significantly (p < 0.05) the responsiveness of lactotrophs to A-II and the PRL secretion in both intact and OVX + EB treated rats increased by 40% and 30% respectively. By contrast, A-II did not produce any statistically significant response of lactotrophs from OVX female rats. At variance to this observation, in all models tested TRH increased significantly the PRL secretion (p < 0.05). The correlation of PRL secretion and morphology of different lactotroph subtypes authenticates the existence of a lactotroph subpopulation unresponsive to A-II in pituitary cell cultures from rats depleted of estrogen.
Assuntos
Angiotensina II/farmacologia , Estradiol/administração & dosagem , Hipófise/efeitos dos fármacos , Prolactina/análise , Vasoconstritores/farmacologia , Animais , Células Cultivadas/efeitos dos fármacos , Retículo Endoplasmático Rugoso/efeitos dos fármacos , Retículo Endoplasmático Rugoso/metabolismo , Feminino , Complexo de Golgi/efeitos dos fármacos , Complexo de Golgi/metabolismo , Imuno-Histoquímica , Microscopia Eletrônica , Ovariectomia , Hipófise/metabolismo , Hipófise/ultraestrutura , Radioimunoensaio , RatosRESUMO
Ultrastructural features and cytokeratin expression of inverted ductal papillomas of minor salivary gland origin were studied. Under the electron microscope, an increased number of desmosomes and mucus-like granules in some cells were the most striking features. Immunohistochemical study revealed that tumor cells displayed strongly positive reactions with cytokeratins 13 and 14, and less strong reactions with cytokeratins 7, 8, 18 and 5D3. These results support the hypothesis that an inverted ductal papilloma can be derived from the proximal portion of a salivary gland excretory duct.