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T Lombardi

Publications and source records attributed to T Lombardi.

69 records · Page 4Linked to original sources
PubMed1988

In vitro modulation of endothelial fenestrae: opposing effects of retinoic acid and transforming growth factor beta.

Cultured endothelial cells isolated from fenestrated capillaries express many properties characteristic of their in vivo differentiated phenotype, including the formation of a limited number of fenestrae. In this study, we have investigated whether physiological factors that control cell differentiation might regulate the surface density of fenestrae in capillary endothelial cells. We have found that treatment of the cultures with retinoic acid (10 microM) induces a more than threefold increase in the surface density of endothelial fenestrae, whereas transforming growth factor beta (TGF beta) (2 ng ml-1) causes a sevenfold decrease in the surface density of these structures. These results show that the expression of endothelial fenestrae is susceptible to bidirectional modulation by physiological signals, and suggest that retinoids and TGF beta may participate in the regulation of fenestral density of capillary endothelium in vivo.

Animals↗
PubMed1987

Phorbol ester induces diaphragmed fenestrae in large vessel endothelium in vitro.

The endothelium of visceral capillaries is fenestrated, whereas that of large vessels is not. We show here that the tumor promoter, 4 beta-phorbol 12-myristate 13-acetate (PMA), triggers formation of diaphragmed fenestrae in endothelial cells cultured from the calf pulmonary artery and the human umbilical vein. This demonstrates that large vessel endothelial cells have the potential to express, in response to exogenous signals, a structural specialization uniquely associated with the endothelium of visceral capillaries in vivo.

Animals↗
PubMed1986

Endothelial diaphragmed fenestrae: in vitro modulation by phorbol myristate acetate.

Cultured microvascular endothelial cells isolated from fenestrated capillaries have been shown to express many properties of their in vivo differentiated phenotype, yet they contain very few diaphragmed fenestrae. We show here that treatment of capillary endothelial cells with the tumor promoter, 4 beta-phorbol 12-myristate 13-acetate, induces more than a fivefold increase in the frequency of fenestrae per micron 2 of cell surface, as determined from a quantitative evaluation on freeze-fracture replicas. In quick-frozen, deep-etched preparations, the endothelial fenestrae appeared to be bridged by a diaphragm composed of radial fibers interweaving in a central mesh, as previously observed in vivo. These results indicate that diaphragmed fenestrae are inducible structures, and provide an opportunity to study them in vitro.

Adrenal Cortex↗
PubMed1986

Loss of polarization of plasma membrane domains in transformed pancreatic endocrine cell lines.

Using enveloped RNA viruses that bud selectively from either the apical or basolateral surface in polarized epithelial cells, we have recently provided evidence for polarization of plasma membrane domains in cultured pancreatic islet cells. In this study, we have followed the same experimental strategy to establish whether these polarized properties are maintained in transformed pancreatic endocrine cells. We find that influenza virus and vesicular stomatitis virus emerge from both the attached and free surfaces of cultured insulinoma cells (RIN cells) and SV40-transformed beta-cells (HIT cells). This demonstrates loss of polarization in transformed pancreatic endocrine cells.

Animals↗
PubMed1986

Direct cell-to-cell transmission of vesicular stomatitis virus.

Vesicular stomatitis virus (VSV) infection of kidney-derived, LLC-PK1 epithelial cells resulted in the budding of new viral particles into the basolateral space of the cultures. In lateral regions where cells were in close apposition, the majority of assembling viral particles in the process of budding from the producing cell had their apex already engaged in clathrin-coated pits of the neighbouring cell surface. These observations suggest that the viral envelope-plasma membrane interaction triggers the focal formation of clathrin-coated pits; they also show how VSV infection could spread throughout a tissue with only minimal exposure to a host's extracellular environment.

Animals↗
PubMed1985

Polarized plasma membrane domains in cultured endothelial cells.

To determine whether distinct plasma membrane domains exist in endothelial cells, we infected monolayer cultures of macro- and microvascular endothelial cells with enveloped RNA viruses known to bud selectively from either the apical or basal surface in polarized epithelial cells. We found that vesicular stomatitis (VSV) and Sendai virus emerge asymmetrically from cultured endothelial cells. This provides direct evidence for the existence of polarized plasma membrane domains in vascular endothelial cells.

Animals↗
PubMedDate not supplied

Evidence for polarization of plasma membrane domains in pancreatic endocrine cells.

Polarization of plasma membrane domains is an essential feature of secretory epithelial cells from exocrine glands. The surface of exocrine cells (a typical example is the acinar cell of the pancreas) is separated into an apical domain, where secretion occurs by exocytosis, and a basolateral domain, which senses variations of the internal milieu and is enriched with receptors for various hormones and secretagogues. It is unknown whether secretion is polarized in endocrine cells (except for thyroid follicular cells, which are organized into cavitary structures). To determine whether distinct plasma membrane domains exist in endocrine cells, we infected monolayer cultures of pancreatic endocrine cells with enveloped RNA viruses known to bud selectively from either the apical or basolateral domain in polarized epithelial cells. This asymmetrical budding is thought to reflect the polarized nature of the infected cells, as in non-polarized cells such as fibroblasts, the same viruses bud nonselectively from the entire cell surface. We show here that influenza virus and vesicular stomatitis virus (VSV) emerge asymmetrically from cultured pancreatic islet cells; this represents the first evidence for polarization of plasma membrane domains in pancreatic endocrine cells.

Animals↗
PubMedDate not supplied

Immunoperoxidase labelling of previously stained tissue sections: application in oral histopathology.

We have investigated by the avidin-biotin peroxidase technique a wide variety of recognized cellular antigens in paraffin sections of both normal and pathological material which have been previously stained with hematoxylin and eosin. The intensity of peroxidase reaction was adequate to permit the diagnosis and the background of the immunoreaction minimal. This technique therefore, appears useful either for retrospective analysis of cellular antigens or when limited unstained material is available.

Acetates↗