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Biomedical subjects

L Diaz-Flores

Publications and source records attributed to L Diaz-Flores.

14 recordsLinked to original sources
PubMed1992

Behavior of postcapillary venule pericytes during postnatal angiogenesis.

Autogeneic bone marrow was implanted into an artificially created cavity in a segment of rat sciatic nerve, after removal of nerve fascicles, without damaging the epineurium or surrounding microcirculation. Under these conditions, the bone marrow induces capillary growth and forms granulation tissue from surrounding tissues, the behavior of pericytes being studied in the preformed (preexisting) postcapillary venules of the latter. Beginning 20 h after bone marrow implantation, the pericytes of the preexisting postcapillary venules hypertrophy, with shortening of their processes, prominent nucleoli, dispersal of ribosomes into their free form, fragmentation of basal lamina, and increased DNA synthesis. The number of contact surfaces between pericytes and endothelium is noticeably lower than in controls. Many pericytes are in mitosis. Cells with a shape transitional between pericytes and interstitial fibroblast-like cells appear. In some cases, Monastral Blue (MB) was used as a marker of the cells in preexisting venule walls of the graft bed. In the earlier stages of the experiment, the MB labelling is restricted to the cytoplasm of pericytes and endothelial cells of postcapillary venules, and to the macrophages that occur in the space between pericytes and endothelium. Furthermore, the marker continues to be observed, at a later stage, in some of the following cells: pericytes and endothelial cells of the newly formed vessels, macrophages migrating into the interstitium, transitional cells between pericytes and fibroblasts, and typical fibroblasts of the granulation tissue. The present study provides greater evidence that preformed microvasculature pericytes are substantially activated during postnatal angiogenesis and granulation tissue formation, suggesting that they may contribute to the origin of new pericytes and fibroblasts.

Aging↗
PubMed1992

Ito cells and fibrogenesis in chronic alcoholic liver disease.

The relationships between the number of Ito cells; serum N-terminal type III procollagen and laminin; clinical and biochemical parameters of liver function derangement; histomorphometrically assessed total amount of liver fibrosis; and daily ethanol intake were studied in 43 patients affected by chronic alcoholic liver disease (10 cirrhotics). Significant correlations were found between serum laminin and N-terminal type III procollagen and histological, clinical and biochemical data of liver function derangement, but no correlation was found between the aforementioned parameters and the percentage of Ito cells, which in turn seemed to be related to ethanol ingestion.

Adipose Tissue↗
PubMed1992

Pericytes as a supplementary source of osteoblasts in periosteal osteogenesis.

In the adult rat femur, lifting a periosteum strip with microscopic bone flakes on its deep surface, if performed without damaging the surrounding microcirculation, rapidly leads to new bone formation and angiogenesis. Using vascular labeling, the pericytes and endothelial cells (ECs) were labeled with monastral blue (MB) in the preformed, preexisting postcapillary venules of the periosteal microcirculation. MB was detectable by light and electron microscopy and it persisted in some of the daughter cells. Between one and 21 hours, the MB labeling was restricted to the pericytes and ECs of postcapillary venules. Immediately afterward, both pericytes and ECs of these vessels were activated and continued to show MB. The phenomenon of pericyte activation includes enlargement, disruption of their basal lamina, separation from the walls of the preformed vessels, and the presence of mitotic figures. At this stage, activated pericytes with MB in their cytoplasm, fibroblast-like cells, and transitional cell forms between them were seen in interstitial areas. After 27 hours, vascular buds appeared and MB was detected in some ECs and pericytes. Between three and six days, when bone-tissue development was observed, some osteoblasts were MB labeled. Previous findings support the hypothesis that when the periosteum is activated, the process of bone formation from cells already present in the periosteum is augmented by proliferation and differentiation of pericytes, which contribute a supplementary population of osteoprogenitor cells.

Animals↗
PubMed1991

Inducible perivascular cells contribute to the neochondrogenesis in grafted perichondrium.

Autogeneic perichondrium was implanted above the cremaster muscle of the rat, and the new formation of two types of cartilage (types I and and II) was confirmed. Also, granulation tissue was observed before the type II cartilage formation. Under these conditions, the contribution to the neocartilage of graft bed derived cells, mainly of the venule pericytes, was studied. To follow the pericyte lineage, we used a marker--Monastral Blue B--the administration of which was based on the principle of vascular labeling. While the perichondrium was kept free, before its implantation, the preformed (preexisting) venules in the cremaster muscle were exclusively labeled with Monastral Blue B, which was incorporated into the cytoplasm of pericytes and endothelial cells. After perichondrium implantation, the following sequence in tracer distribution was demonstrated. During the earlier stages, labeling was restricted to the pericytes and endothelial cells of venules in the graft bed. Later the tracer was observed in some endothelial cells and pericytes of the growing vessels and in fibroblast-like cells of the granulation tissue. Finally, some type II neochondrocytes appeared labeled. Tracer was not found in type I neochondrocytes. The presence of label in type II neochondrocytes demonstrates that they arise from progenitor cells present in the graft bed, principally from small venule pericytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Proliferative fasciitis: ultrastructure and histogenesis.

The ultrastructure was studied of 2 cases of proliferative fasciitis (PF) which affected the fascia and subcutaneous fat. Two basic cell types were observed in the lesions: fibroblast-like, and giant cells. The fibroblast-like cells had myofibroblastic ultrastructural characteristics. The giant cells showed a well-developed, rough endoplasmic reticulum, irregularly distributed filaments and clear lipid droplets in their cytoplasms. Ultrastructurally, the giant cells seemed to belong to a cellular line capable of synthesizing ground substances and extracellular fibers, but with a modified phenotype. A consistent feature was the presence of nodular aggregates of numerous proliferating perivascular cells. Transitional forms between perivascular, fibroblast-like, and giant cells were observed. Our hypothesis is that perivascular cells (activated pericytes) are the source of the fibroblast-like and giant cells in proliferative fasciitis.

Fascia↗
PubMed1988

Growth of two types of cartilage after implantation of free autogeneic perichondrial grafts.

The perichondrium of adult rats was dissected from the posterior side of the ear where a plane of separation can be easily found between the superficial chondrocytes and the rest of the cartilage. When pulled off, the perichondrium brings with it a cartilaginous strip adhered to its inner layer, with the detachment surface showing projections of broken capsular matrix (PBCM). The perichondrium and subperichondrial cartilage were then transferred as autogeneic grafts to preformed muscle pockets of the abdominal wall and to everted vein chambers placed free in the iliac blood flow. During a period of one to 12 days, chondrogenesis was studied in the grafts and in the graft bed areas next to subperichondrial cartilage. When the perichondrium was placed into a muscular pouch, wherein perichondrocytes survived and a prominent vascular ingrowth in the graft bed was observed, the presence of two types of newly formed cartilage was demonstrated (Types I and II). These types showed differences in their location, time of appearance, and microscopic characteristics. Type I neocartilage appeared in the inner layer of the perichondrium on the third or fourth day after grafting; at this time the cells, surrounded by a well-defined capsular matrix, were large, darkly stained, and highly electron dense. Type II neocartilage, separated from Type I by the PBCM, appeared in the graft bed area located within perichondrial folds on the sixth or seventh day after implantation. Their cells showed a poorly defined capsular matrix and were smaller, lighter stained, and less electron dense than those of Type I. When the perichondrium was transplanted to everted vein chambers placed in the iliac blood flow, wherein perichondrocytes survived and vascular ingrowth from the graft bed was not present, Type I neocartilage was formed but Type II was not. The morphologic and histoautoradiographic findings in these studies suggest that Type I cells come from perichondrocytes of the inner perichondrial layer, whereas Type II cells originate from the undifferentiated perivascular mesenchymal cells of the graft bed.

Animals↗
PubMed1985

Relation between arterial intimal thickening and the vasa-vasorum.

The histopathological data presented support a new concept for the origin of the cells which cause intimal thickening of arteries. Arterial segments, isolated between ligatures, when examined by intravascular contrast techniques, showed penetration of vasa-vasora and formation of intra-arterial granulation tissue which produced myointimal thickening. Transitional forms between pericytes and myointimal cells were found. In autoradiographic studies on the incorporation of 3H-thymidine, DNA synthesis was first seen in the adventitia, fundamentally in the vasa-vasora pericytes, and in the adjacent media, and later in the intimal thickening. In arterial segments between ligatures typical intimal thickening was produced when intra-arterial granulation tissue was formed and the ligatures were removed thus restoring the circulation. These results were not produced when the arterial segment was sectioned lengthways between ligatures. It is suggested that this intimal thickening originates in cells from the vasa-vasora, in particular from pericytes.

Animals↗
PubMed1979

[Elastofibroma].

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Age Factors↗
PubMed1976

Electron microscopic evidence for phagocytic properties of human peripheral mononuclear cells cultured with PHA.

The time course of the ultrastructural changes induced in human peripheral mononuclear cells, when cultured with PHA, has been studied. In addition to findings common to many mitotic cells, such as an increase in nuclear and nucleolar size, the presence of free polyribosomes, glycogen and lipid globules in the cytoplasma, and a high number of mitochondria, agglutinating properties due to PHA per se were observed in the first 12 hours. At 72 hours certain cells developed phagocytic-like properties, i.e. they were able to incorporate both material from the extracellular compartment and syngeneic cells. These results are discussed suggesting the possible presence of macrophages in culture or the ability of activated T cells to express it.

Cells, Cultured↗