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M A Mancini

Publications and source records attributed to M A Mancini.

51 records · Page 3Linked to original sources
PubMed1989

Retinovitreal neovascularization in the Royal College of Surgeons rat.

Retinovitreal blood vessels, which we have previously reported in the dystrophic retinas of approximately 20% of older (greater than 15 months of age) spontaneously hypertensive (SHR) rats, also occur in about 20% of retinal dystrophic Royal College of Surgeons (RCS) rats greater than 1 year of age. We have demonstrated previously that these vessels, in the SHR rat, have the anatomic characteristics of retinovitreal neovascularization as it has been described in vasoproliferative retinopathies in humans (1). We now provide strong evidence that the endothelial cells and pericytes of the retinovitreal vessels that occur in RCS rats are proliferating, since they demonstrate by autoradiography significantly increased nuclear labeling with [3H]-thymidine over intra-retinal or choroidal vessels, or the abnormal vessels that grow within the retinal pigment epithelium in these dystrophic retinas. One important difference between the neovascularization that occurs in these rats and that which is observed in various human retinal vascular diseases is the frequent association of the new vessels in dystrophic rat retinas with surrounding cords of proliferating retinal pigment epithelium. The retinovitreal vessels in these strains of dystrophic rats represent a new animal model that may be useful for studying the fundamental processes underlying new blood vessel growth in the retina.

Animals↗
PubMed1989

A cell line derived from non-neoplastic human neuroretinal cells.

We have derived a cell line from an epiretinal membrane excised surgically from a premature female infant born at a gestational age of 25 weeks, and who developed stage 5 retinopathy of prematurity. The cell line, which in early passages appeared immunocytochemically to contain cells with both neuronal and glial characteristics, has been maintained in culture for 14 months at the time this manuscript was submitted, and has survived 20 passages. The cells have a diploid, human karyotype, with most cells possessing 46 normal appearing chromosomes, including 44 autosomes and two X-chromosomes. Morphologically, the cell line at early passages consisted of polygonal cells and also of cells possessing long, spindly branching processes. These two cell types were cloned. Nearly 100% of the cells of both morphologic types in mixed cultures stained immunocytochemically for neuron-specific enolase (NSE), a neuronal marker, and approximately 5-10% of the cells in mixed cultures (including about 50% of the cells with the spindly morphology, that were less prevalent in mixed cultures) stained for glial fibrillary acid protein (GFAP), a glial marker. We have not performed "double-label" immunocytochemistry, but it was evident from the proportion of cells that stained with each marker that many cells must contain both GFAP and NSE. At least 50% of the cells in most of the early cultures were positive for keratin, while all were (and remain) negative for muscle actin. No cells are found that are immunocytochemically positive for factor VIII, a vascular endothelial cell marker. These cultured cells have also been studied immunocytochemically for their production of extracellular matrix substances. The cultures are immunocytochemically positive for type IV (but not type I) collagen, laminin and fibronectin. In later passages, cells of both clones lost their immunocytochemical positivity for GFAP and NSE, and all became positive for keratin. Cells of both clones also developed a similar, polygonal morphology, lacking long processes. By electron microscopy, many of the cells were seen to possess nonmotile cilia, with a 9 + 0 pattern of microtubule doublets. This cell line may be useful for studies of human retinal cell development and metabolism, and responses to pathological processes.

Cell Division↗
PubMed1988

Changes in transcriptional activity and matrix association of alpha 2u-globulin gene family in the rat liver during maturation and aging.

Hepatic synthesis of alpha 2u-globulin in the male rat begins at puberty (about 40 days), reaches a peak level at about 80 days, and ceases at about 750-800 days of age. The age-dependent changes in alpha 2u-globulin synthesis are correlated with both the steady-state level of the hepatic mRNA for this protein and the rate of transcription of the alpha 2u-globulin gene family. Transcriptional activation of the alpha 2u-globulin gene family at puberty and cessation of transcription at senescence correlate with the association and dissociation of this gene domain with the nuclear matrix. Unlike the alpha 2u-globulin gene, the albumin gene in the liver shows preferential association with the nuclear matrix throughout the life. From these results we conclude that the age-dependent changes in alpha 2u-globulin synthesis are due to the alteration in the rate of transcription of the alpha 2u-globulin gene, and that the association of this gene domain to the nuclear matrix is a prerequisite to its transcriptional activation.

Aging↗
PubMed1988

Leupeptin-mediated alteration of renal phagolysosomes: similarity to hyaline droplet nephropathy of male rats exposed to unleaded gasoline.

alpha 2u-Globulin, a protein of hepatic origin found in the urine of male rats, is accumulated in the kidney cortex during exposure to unleaded gasoline and has been implicated in the development of fuel hydrocarbon-induced nephropathy and renal neoplasia. The principal morphological feature of gasoline-induced nephropathy is accumulation of hyaline droplets (enlarged secondary lysosomes or phagolysosomes) in epithelial cells of the proximal convoluted tubule S1 and S2 segments. Inhibition of cathepsin B (a major lysosomal peptidase) by treatment of male rats with leupeptin causes rapid accumulation of phagolysosomes and alpha 2u-globulin in the kidney very similar to gasoline exposure. Further, the renal cortical subcellular distribution of alpha 2u-globulin, determined with an electron microscopic immunochemical method, is almost totally confined to phagolysosomes following administration of either gasoline or leupeptin. These results, taken together, indicate that the mechanism of nephrotoxicity of gasoline involves inhibition of renal phagolysosomal proteolysis.

Alpha-Globulins↗
PubMed1988

ATP causes retinal pericytes to contract in vitro.

We evaluated the contractility of bovine retinal microvascular pericytes in culture by permeabilizing the cells with 0.1% Triton X-100 and measuring their response to MgATP. Sequential photographs of the cells were taken over 20 min and their surface areas were measured. Our study directly demonstrates that pericytes are contractile cells, which respond to MgATP in a dose-dependent fashion over a relatively short time course (minutes). Pericytes did not contract in response to GTP, pyrophosphate or beta, gamma-methylene ATP. Immunofluorescence study showed the presence of muscle actin in Triton X-100-treated cells before and after contraction, indicating preservation of this cytoskeletal protein even after treatment with the detergent. Similar experiments on human umbilical vein endothelial cells, bovine lens epithelial cells and human retinal pigment epithelial cells showed that these cells were significantly less contractile than retinal pericytes. That pericytes show substantial contraction over a short time course indicates that these cells may play a major role in regulating blood flow in the microcirculation.

Actins↗
PubMed1987

Sex-independent synthesis of alpha 2u-globulin and its messenger ribonucleic acid in the rat preputial gland: biochemical and immunocytochemical analyses.

alpha 2u-Globulin is the principal urinary protein of the mature male rat. The major urinary source of this protein is the liver where it is synthesized and secreted by hepatocytes under hormonal regulation. High levels of alpha 2u-globulin and its messenger RNA (mRNA) are also present in the preputial gland of both male and female rats, and neither castration nor ovariectomy significantly alters the preputial concentration of this protein and its mRNA. Per unit mass of RNA and protein, the preputial gland as compared to liver contains about 3-fold higher level of alpha 2u-globulin mRNA and about 300-fold higher level of alpha 2u-globulin. Despite a 3-fold (300%) difference in the content of alpha 2u-globulin mRNA, nuclear run-off experiments show only a 30% higher rate of alpha 2u-globulin gene transcription in the preputial gland than in the liver. Immunocytochemical analyses reveal that the liver possesses two alpha 2u-globulin cell populations, one showing higher immunoreactivity than the other. In contrast, the preputial gland contains only one type of alpha 2u-globulin containing acinar cells, and a large amount of alpha 2u-globulin accumulates in the ductal lumen. From these results we conclude that the 300% higher level of alpha 2u-globulin mRNA in the preputial gland is not due to a corresponding difference in the rate of transcription of alpha 2u-globulin gene. Such a difference may represent tissue-specific regulation at a posttranscriptional level of mRNA metabolism. Furthermore, the huge difference in the alpha 2u-globulin content of the preputial gland and the liver is primarily due to the cellular and ductal accumulation of this protein in the preputial gland vs. its rapid secretion by the liver.

Alpha-Globulins↗
PubMed1987

Pericyte coverage is greater in the retinal than in the cerebral capillaries of the rat.

Using electron microscopic morphometry, we demonstrate here that, in the albino rat, the pericytes of the retinal microcirculation over the capillary circumference much more extensively than in five widely separate regions of cerebral cortex. The ratio of pericyte plasma membrane length in contact with the vascular circumference, to the outer circumference of the endothelial cell tube, was 0.41 +/- 0.02 (SEM) for the retinal microvessels, and ranged from 0.22 +/- 0.02 to 0.30 +/- 0.03 for the five regions of cerebral cortex. The values of this ratio for the retina differed significantly from those for the various cortical regions. Differences of comparable magnitude were obtained between ratios of pericyte to endothelial cell areas in retina and cerebral cortex. The substantial quantitative difference in pericyte coverage of the microvessel circumference between the retinal and cerebral microcirculations may have important implications for normal and pathological microcirculatory dynamics in these two organs.

Animals↗
PubMed1986

Retinal dystrophy: development retarded by galactose feeding in spontaneously hypertensive rats.

Retinal photoreceptor cell dystrophies have been widely observed in humans and in animals, but pathogenetic mechanisms are known in only a few such disorders, and successful therapeutic intervention has been reported in fewer still. Spontaneously hypertensive albino rats develop a retinal photoreceptor cell dystrophy with onset late in the first year or early in the second year of life. Between 60 and 70 percent of the animals are affected. A substantial reduction in the prevalence and severity of the dystrophy occurred in such animals whose diet contained 30 percent (by weight) D-galactose. Neither an inhibitor of the enzyme aldose reductase, present in the diet, nor diabetes mellitus, induced by streptozotocin, had any statistically significant influence on the dystrophy. Ambient light and systolic blood pressure levels also did not seem to influence the course of the disorder. The mechanism by which galactose exerts its effect is unknown, but a mutant enzyme with an elevated Michaelis constant (Km) for galactose is plausible.

Age Factors↗
PubMed1986

Collagens of the retinal microvascular basement membrane and of retinal microvascular cells in vitro.

We have analysed the collagens present in vascular basement membranes isolated from bovine retinal and cerebral microvessels and bovine renal glomeruli, and from the non-vascular basement membrane of bovine lens capsule. These are compared with the collagens produced by cultured bovine retinal microvascular pericytes and lens epithelial cells, and by canine retinal microvascular endothelial cells, in vitro. Biochemical and immunocytochemical analyses indicate that all of the vascular basement membrane preparations have an identical collagenous composition, consisting of the same polypeptides present in lens capsule (primarily type IV collagen), together with other polypeptides that are identified as type I, and a small amount of type III collagen. Identification of the latter is based on two-dimensional gel electrophoresis in the presence and absence of a reducing agent. Immunocytochemical studies, however, demonstrate type I, type IV and some type V collagen in the basement membranes of the isolated microvessels. The cultured microvascular cells produce predominantly type I collagen molecules, but they also produce other collagen peptides that appear to be type IV, and, at least in some experiments, small amounts of type III collagen. The biochemical identification of collagens type I and IV is confirmed by immunocytochemistry. However, results with anti-type I collagen and procollagen antibodies in cultured pericytes vary with antibodies from different sources. The quantities of the type IV peptides produced by the cultured cells also vary in different experiments.

Amino Acids↗
PubMed1986

Cellular interactions in the hormonal induction of alpha 2u-globulin in rat liver.

The role of hepatocellular interaction in the androgen-dependent synthesis of rat alpha 2u-globulin was examined by immunochemical analysis of liver sections. Both after androgen administration to the ovariectomized female and during puberty in the male, only a subpopulation of hepatocytes became competent to synthesize alpha 2u-globulin. These competent hepatocytes first appeared as discontinuous patches along the wall of the central vein. After the formation of a confluent layer around the central vein, cellular competency was seen to propagate toward the periportal direction through the cords of hepatic cells. Although the periportal progression of cellular competency for the synthesis of alpha 2u-globulin appeared to be an all-or-none phenomenon, it did not require cell division. From these results we conclude that certain components of the central vein are necessary for the hormonal induction of alpha 2u-globulin in the rat liver. We also propose that a primary endocrine influence on the hepatic vein results in the production of a secondary paracrine mediator which can trigger the synthesis of alpha 2u-globulin in adjacent hepatocytes. Perivenous to periportal flow of this putative secondary mediator can explain cell recruitment for the synthesis of alpha 2u-globulin along the hepatic cords.

Alpha-Globulins↗
PubMed1986

Presumed retinovitreal neovascularization in dystrophic retinas of spontaneously hypertensive rats.

The authors have observed abnormal blood vessels, strongly suggestive of neovascular proliferation, arising from the retinal circulation and extending through the inner limiting membrane of the retina into the vitreous in five spontaneously hypertensive (SHR) rats with severe retinal dystrophy. The animals in whom these presumptive retinovitreal new vessels occurred were all 15 mo of age or older. The new vessels frequently demonstrated thinned and, rarely, fenestrated endothelium, abnormal intracellular junctions, increased numbers of endocytic vesicles, bizarre appearing pericytes, and highly abnormal basement membranes, features that have been observed in retinovitreal new vessels in proliferative retinopathies in humans. Unlike such new vessels arising from the human retinal circulation, however, those that we observed in dystrophic rat retinas were usually surrounded by proliferating retinal pigment epithelial cells within the retinal substance. Unlike the vessels, the pigment epithelial cells did not break through the inner limiting membrane of the retina to enter the vitreous. The pigment epithelial cells that made contact with the internal limiting membrane of the retina demonstrated apical and basal plasma membrane specializations that are typical of these cells in their normal anatomical location, while pigment epithelial cells migrating in cords through the neural retina lacked such specializations. This animal model may be of great value in understanding the mechanisms of retinal neovascularization.

Animals↗
PubMed1986

In vitro production of glycosaminoglycans by retinal microvessel cells and lens epithelium.

Analysis of bovine lens capsules and retinal microvessel basement membranes by cellulose acetate electrophoresis, together with treatment by specific enzymes or by nitrous acid, reveals that heparan sulfate is the only demonstrable glycosaminoglycan (GAG), consistent with the observations of most other investigators on basement membrane preparations from several different tissues. When bovine retinal microvessel pericytes or endothelial cells or bovine lens epithelial cells are grown in culture in the presence of [35S]-sulfate or [3H]-glucosamine, however, both cellulose acetate electrophoresis and gel filtration chromatography reveal that the cultured pericytes synthesize primarily chondroitin sulfate, whereas the lens epithelial cells and microvascular endothelial cells produce a mixture of GAGs consisting of approximately 60% heparan sulfate and 40% chondroitin sulfate. The chondroitin sulfate chains have an Mr of 70,000, but the Mr of the heparan sulfate chains is 10,000, based on gel filtration chromatography on Sepharose CL-6B. Hence, cell culture conditions may produce phenotypic modulation of the biosynthetic capacities of these cells for GAGs. However, the difference between the in vitro and in vivo findings may in part be explained if many of the chondroitin sulfate GAGs synthesized in vitro are cell associated and are not incorporated into the basement membrane.

Animals↗
PubMed1986

Does the retinal pigment epithelium polarize the choriocapillaris?

Morphometric evaluation of choroidal capillaries from spontaneously hypertensive (SHR) rats with anatomically normal and severely dystrophic retinas reveals a marked polarization of endothelial fenestrations, endothelial cytoplasmic thickness, and endothelial cell nuclei. The mean density of fenestrations per unit endothelial length is greatest and the cytoplasmic thickness and number of nuclei is least in capillary sectors closest to the retinal pigment epithelium (RPE), with a statistically significant, continuous decrease in density of fenestrations and an increase in endothelial thickness and nuclear numbers in sectors progressively farther from the RPE. Abnormal capillaries derived from the retinal circulation and growing within the RPE also have fenestrations, but show no anatomic polarization. These results are consistent with the recently proposed hypothesis that a diffusible, trophic factor, produced by the RPE and secreted from its basal surface, modulates the structure of nearby vascular endothelial cells. However, the endothelial cells themselves probably also influence the structure of the RPE, since complex infoldings of the RPE plasma membrane, identical to those normally present in its basal surface, are also extensively present surrounding the abnormal intra-RPE capillaries.

Animals↗