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N Buyssens

Publications and source records attributed to N Buyssens.

At least 19 recordsLinked to original sources
PubMed1994

The relationship between pre-existing subendothelial smooth muscle cell accumulations and foam cell lesions in cholesterol-fed rabbits.

We investigated whether pre-existing subendothelial smooth muscle cell (SMC) accumulations in cholesterol-fed rabbits are transformed into foam cell plaques. Twenty-four rabbits received a standard diet supplemented with 2% cholesterol for 4 or 8 weeks. Six rabbits received a supplement of 0.3% cholesterol for 35 weeks. The aorta and other systemic and pulmonary vessels were studied by immunohistochemistry for smooth muscle cells SMC (alpha-SMC actin), macrophages (RAM11), cell replication (proliferating cell nuclear antigen) and endothelial cells (von Willebrand factor; vWF). Initially the foam cell plaques were composed exclusively of foam cells of macrophage origin (MFC). In more advanced lesions SMC and collagen fibres were also present, leading to a fibrous transformation of the plaque. Cell replication was mainly located in the MFC. The endothelial cells covering the plaques showed an increased immunoreactivity for vWF which was also deposited in the interstitium between the FC. Pre-existing subendothelial SMC did not transform into FC. The newly formed FC plaques remained clearly separated from the pre-existing subendothelial SMC. The development of the plaques can be attributed not only to monocyte recruitment but also to macrophage multiplication.

Animals↗
PubMed1994

Hyperplasia, hypertrophy, and phenotypic alterations in the distal nephron after acute proximal tubular injury in the rat.

BACKGROUND: Little is known about the impact of acute proximal tubular injury and dysfunction on the distal nephron. EXPERIMENTAL DESIGN: Selective necrosis of the kidney proximal convoluted tubule (PCT) was induced in rats by subcutaneous injection of the aminoglycoside gentamicin during 2 days. Damage and repair were measured until complete morphologic recovery after 10 days. Special attention was given to structural and biochemical alterations in the distal nephron. RESULTS: In control animals, cellular turnover, measured by immunohistochemical staining for proliferating cell nuclear antigen, was higher in distal than in proximal tubules. After injury, the strongly increased cell proliferation in regenerating necrotic PCT was preceded by an equally important proliferation in the distal tubules of the cortex and outer stripe of the outer medulla in the absence of necrosis but displaying enhanced apoptosis. Yet, epithelial vimentin expression was restricted to regenerating PCT. A temporary loss in the amount of immunostainable epidermal growth factor in the distal nephron was paralleled by a similar reduction in Tamm- Horsfall protein and transferrin receptor staining and in peanut and Helix pomatia lectin binding. Furthermore, the epithelial area/nucleus in the cortical distal tubules was increased by 71%, 6 days after the onset of acute renal failure; this hypertrophic condition was confirmed ultrastructurally. After full recovery of the PCT, a second burst in proliferative activity occurred in the hypertrophic distal segments in the absence of apoptosis. In the regenerated PCT, an excess cell number was accompanied by increased apoptotic activity. CONCLUSIONS: Development of distal tubular hypertrophy after PCT necrosis may be a compensatory response to a transient loss of proximal tubular function. The early reduction in staining for epidermal growth factor and other distal tubular markers in the presence of apoptosis and hyperplasia indicates transient phenotypic simplification and implies that renal epidermal growth factor is unlikely to control PCT regeneration.

Animals↗
PubMed1993

Longitudinally oriented smooth muscle cells in rabbit arteries.

Intima formation in vessels, spontaneous or experimentally induced, is generally characterized by the presence of longitudinally oriented smooth muscle cells (LSMC). During an experiment of neo-intima induction in carotid arteries in rabbits, by application of a non-constrictive silastic cuff, a study was performed to investigate the presence of LSMC in the systemic and pulmonary circulations, in both elastic and muscular arteries. Three patterns could be distinguished: intimal cushions in muscular arteries, single or small groups of LSMC in the intima in elastic and larger muscular arteries, and intra-medially located layers or columns of LSMC in the aorta, the pulmonary artery, at the bifurcation of the aorta and around orifices of branches. In order to understand this peculiar orientation a biomechanical approach was used: this showed that near the lumen the circumferential stress is 4.5 times higher than the longitudinal. Because the cell surface of the smooth muscle cells exposed to this stress per unit vessel length is much less in the longitudinal than in the circular direction we conclude that the LSMC align in the direction which allows them to cope most effectively with the mechanical stresses.

Animals↗
PubMed1993

Ultrastructural demonstration of type IV collagen deposits in periductal elastosis in breast cancer.

In a previous study we demonstrated at light microscopical level the presence of variable amounts of type IV collagen in the areas of periductal and interstitial elastosis in breast cancer. The present work was directed towards a further study by immunoelectron microscopy of the distribution of type IV collagen in the areas of periductal elastosis. The semithin sections showed a distinct immunoreactivity of all basement membranes for type IV collagen but no staining of the interstitial stroma. Corresponding ultrathin sections demonstrated a broad basement membrane with immunoreactivity for type IV collagen at its outer side. Many punctiform deposits of type IV collagen were observed in the areas of periductal elastosis but not around normal ducts or vessels. Recently the role of type IV collagen as a structural component on anchoring plaques between the basement membrane and the underlying stroma in the dermis has been emphasized. The results of this study demonstrate the presence of type IV collagen deposits below a thickened basement membrane in breast cancer.

Breast Neoplasms↗
PubMed1992

Effect of ageing and malnutrition on rat myocardium. I. The myocyte.

The effects of ageing and starvation on the rat myocardium were studied by morphometric methods. Since cardiac muscle is a tissue with a high level of anisotropy, methods based on the concept of vertical planes were used to describe quantitative alterations in the rat myocyte both at the cellular and ultrastructural level. During starvation rapid and important changes were noted, particularly in the transverse dimension of cells and organelles. The most striking change, however, was the immediate dilatation of the myocyte T-system, reflecting an adaptive interaction between the intra- and extracellular environment. At the same time exocytosis of intracellular components into the extracellular space of the T-system was observed. The ratio of mitochondria to myofibrils decreased progressively during starvation. Such a decrease, in general, may reach a point when cellular energy supply becomes compromised. A comparison between different regions of the heart showed no differences and it can be concluded that the morphological changes during starvation are the same, and equally distributed, in both ventricles. The changes described in the aged rat heart point in the direction of a hypertrophy of the aged myocyte. This leads to a lower ratio between surface and volume which finds its representation at the subcellular level in a more spherical shape of nuclei and mitochondria. Unlike what is seen in malnutrition, the mitochondrial/myofibril ratio is higher in the older rat. From the morphological point of view, the atrophy of malnutrition and the hypertrophy of ageing are opposed, but in both there is a change in the relationship of the myocyte to its environment which directly influences the substrate exchange capacity. This tends to protect the myocyte in starvation but jeopardizes the older cell.

Aging↗
PubMed1992

Effect of ageing and malnutrition on rat myocardium. II. The microvasculature.

The modulating effects of ageing and malnutrition on rat myocardium were studied morphometrically with respect to the microvasculature. An increase in capillary density together with a decrease in capillary lumen cross-sectional area was noted during starvation. The important changes seen in the myocyte T-system were paralleled by a decreased diffusion distance for oxygen from the capillary lumen to the mitochondrion. The changes described in the aged rat heart point to an altered inter-relationship between parenchyma and vascularization with a lower capillary volume fraction and a greater diffusion distance from the capillary lumen to the mitochondrion; this is caused by hypertrophy of the aged myocyte. This reduction in capacity to exchange substrates is further reduced by the less developed T-system in the older myocyte.

Aging↗
PubMed1992

A standardized surgical technique to obtain a stable and reproducible chronic renal failure model in dogs.

The remnant kidney, a model of chronic renal failure in animals, can be obtained by two techniques: either surgical removal of tissue of one kidney, combined with contralateral nephrectomy or inducing necrosis of kidney tissue by ligation of branches of the renal artery of one kidney combined with contralateral nephrectomy. In the literature, most reports concern the ligation technique. The technique is safe and simple but the results in dogs are unpredictable. In this paper, both techniques were compared. We could demonstrate that the unpredictable result of the ligation technique is due to the formation of collateral vessels bypassing the ligated branches and to the inconstant ramification pattern of the renal artery. In this study, a standardized technique consisting of the resection of 16-18 g of tissue of one beagle kidney and removal of the other one is described. This method results in a stable chronic renal failure until the dogs are sacrificed at 9-12 months.

Angiography↗
PubMed1992

Quantitative relationships between body weight, kidney weight and nephron size in mongrel dogs.

Mammalian species of large stature have larger kidneys with larger nephrons than smaller animals, although this relationship is not linear. In order to investigate whether in animals of different sizes within the same species similar differences exist, a study in mongrel dogs was undertaken. In animals weighing between 9 and 42 kg with kidney weights from 25 to 79 g the area and perimeter of the glomeruli and the cortical width were measured. The number of glomeruli per unit area was counted and corrected for the size of the glomeruli. The results show that larger dogs have larger kidneys and that this enlargement is due to the increase in size of the nephrons and not in their number.

Animals↗
PubMed1991

Ridogrel prevents the thromboxane-mediated pressor response and oedema induced by hydrogen peroxide in isolated rabbit lungs.

Perfusion of isolated rabbit lungs with hydrogen peroxide (H2O2, 3 x 10(-5) M) raised the overflow of thromboxane B2 (TXB2) and the perfusion pressure. H2O2 induced oedema formation and endothelial distress, as evidenced by an increased production of 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha). Endothelial cell death did not occur since there was no release of lactate dehydrogenase. The thromboxane A2 (TXA2)-synthase inhibitor/receptor antagonist ridogrel (R68070) further enhanced 6-oxo-PGF1 alpha output, while inhibiting TXB2 release. Ridogrel prevented the rise in pulmonary artery pressure and oedema formation. These data indicate that TXA2 is probably involved in the acute pulmonary pressor response and concomitant oedema formation induced by H2O2. In order to assess the functional activity of the pulmonary endothelium, the uptake of 5-hydroxytryptamine (5-HT) was measured before and 15 min after exposure to H2O2. As the H2O2-induced effects were not associated with any change in the uptake of 5-hydroxytryptamine (5-HT), we conclude that the endothelial injury was reversible or that the 5-HT uptake was not sensitive enough to evaluate the integrity of the pulmonary endothelium during oxidant-induced injury.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Neointima formation impairs endothelial muscarinic receptors while enhancing prostacyclin-mediated responses in the rabbit carotid artery.

The purpose of this study was to determine whether the generation of a neointima, an early step in the development of atherosclerosis, affects endothelium-dependent or -independent vasodilation. The neointima was induced, within 7 days, by positioning a nonocclusive silicone collar around one carotid artery in rabbits. After 1, 2, 7, or 14 days segments were cut from the collar-surrounded region of this artery as well as from the sham-operated contralateral artery and were used for isometric tension recording or for bioassay of nitric oxide (NO). The acetylcholine-induced release of NO was significantly reduced at 7 days. The tension recordings suggested that this already occurred at the earliest stages of neointima formation. Neither the capacity of the endothelial cells to form NO in response to the calcium ionophore A23187 nor the capacity of the underlying smooth muscle cells to relax in response to sources of exogenous NO (3-morpholinosydnonimine and nitroglycerin) was affected by the neointima. Therefore, the impaired endothelium-dependent relaxations to acetylcholine are presumably due to a defect at the level of the endothelial muscarinic receptors. The presence of a fully developed neointima did not alter the responsiveness to isoproterenol and forskolin but enhanced prostacyclin-mediated responses (assessed by iloprost and 13-hydroxyoctadecadienoic acid). These results illustrate selective alterations of endothelial and smooth muscle cell function in intima generation before fatty streak formation.

Animals↗
PubMed1991

Stromal populations and fibrosis in human long-term bone marrow cultures.

An immunofluorescence study of the adherent layer of human long-term bone marrow cultures (HLTBMC) revealed the following surface markers on the different stromal cell populations: stromal fibroblastic cells CD10+, FIB86.3+, CD13+, CD71+; adipocytes CD10+, FIB86.3-, CD13+, CD71-/+; and macrophages CD10-/+, FIB86.3+, CD13+, CD71-/+, CD14+, CD33+, CD25+, HLA-DR+, CD4+, CD19+, CD45+. The markers of the stromal fibroblastic cells in HLTBMC were similar to those of twice-passaged fibroblasts not only from bone marrow and spleen, but also from a hemopoietic non-supportive organ such as the skin. Some of the cultured human umbilical vein endothelial cells used as controls were found to be CD25+, demonstrating for the first time the interleukin-2 receptor p55 chain on normal non-hemopoietic cells. The stromal fibroblastic cells are overrepresented compared to the small non-macrophage hemopoietic cell population in the adherent layer of HLTBMC. In addition, silver staining revealed an increased reticulin content in most of the HLTBMC. An excessive growth of stromal fibroblastic cells and an excessive deposition of their product, the reticulin fibers, are the hallmark of myelofibrosis. The finding of equivalent observations in HLTBMC suggests that the hitherto unexplained, premature quenching of hemopoiesis in HLTBMC might at least partly be due to mechanisms similar to those operating in myelofibrosis in vivo.

Antigens, CD↗
PubMed1990

Heat-stable alkaline phosphatase as a marker for human and monkey type-I pneumocytes.

The expression of the heat-stable isoenzyme of alkaline phosphatase in the human and monkey (Macaca mulatta, M. fascicularis) lung was investigated at the light- and electron-microscopic level, using cytochemical techniques and immunocytochemical procedures based on monoclonal and polyclonal antibodies against human term-placental alkaline phosphatase. Both in man and monkey, the enzyme was present in type-I pneumocytes. In the monkey, the enzyme was found in all type-I cells. In man, strong staining was observed only in some type-I cells and in certain cuboidal respiratory bronchiolar cells. Staining was localized on the apical and basal plasma membrane, in apical and basal caveolae, and in the underlying basement membrane. The level of heat-stable alkaline phosphatase expression in the human lung was 10-fold lower than in the monkeys studied. In human fetal lung, the onset of heat-stable alkaline phosphatase expression was associated with the development of the alveolar epithelium from 17-20 weeks gestation onward. It is concluded that: (1) heat-stable alkaline phosphatase is a specific constituent of type-I pneumocytes in man and monkeys; and (2) its subcellular localization may explain its rapid appearance in the circulation under certain conditions.

Alkaline Phosphatase↗
PubMed1990

Basement membrane changes in atrophic tubules in the human kidney.

Changes in the basement membrane (BM) in atrophic tubules in human kidney biopsies were studied by electron microscopy and by immunohistochemistry on cryostat sections with antibodies against collagen type I, type III, type IV, laminin, EMA, keratin and vimentin. The BM showed different degrees of thickening with formation of reduplications which contained fibrocytes. Remnants of cytoplasm of epithelial cells and fibrocytes were incorporated in the thickened BM. This showed signs of lysis and disintegration, indicating that the redundant BM formed by the epithelial cells is removed, although imperfectly, by interstitial cells. Thinning of the BM was another frequent finding. Immunohistochemistry showed a clear reactivity for collagen type IV and laminin in all BM material. The epithelial cells showed multilayering and a peculiar type of dark cells extending underneath adjacent cells and separating them from their BM attachment.

Antigens↗
PubMed1990

A study of the so-called neurotization of nevi.

Fourteen nevi with neuroid zones were examined and compared with nine nevi without neuroid structures. At light microscopic level, nevus cells from the neuroid nevi and the control nevi show the same staining pattern with polyclonal antibodies against S-100 protein. Around the cells of the neuroid zones is a more intensive immunoreactivity with monoclonal antibodies against laminin and collagen type IV than around the nevus cells in the upper dermis and the nevus cells in the control nevi. Also, the Gordon-Sweet stain for reticulin shows a dense network around the cells of the neuroid zones. No immunoreactivity in the neuroid zones was found with monoclonal antibodies against myelin-basic protein, myelin-associated protein, and glial fibrillary acidic protein. At the electron microscopic level, nevus cells from the neuroid zones show stacks of elongated cytoplasmic processes surrounded by basal lamina material. This pattern explains the presence of the abundant cytoplasm seen at light microscopy. Because no features of neural or neurolemmal differentiation could be found, the exactitude of the term neurotization can be questioned.

Antigens, Surface↗
PubMed1990

Comparison of cell growth in different parts of breast cancers.

This study was performed to answer the question: which parts of breast cancers are active in terms of proliferation as measured by the Ki-67 antibody and in terms of cell division as measured by the mitotic index. Forty-six breast samples were studied, including 34 breast cancers and 12 benign conditions. The intraductal component of infiltrating breast cancers showed a significantly lower proliferation index than the infiltrating component. The cells at the periphery of infiltrating tumour strands showed a higher proliferation activity than the cells in the core. These findings suggest that infiltration advances through preferential active growth of the cells at the invasion front.

Antigens, Surface↗
PubMed1990

The presence of a type IV collagen skeleton associated with periductal elastosis in breast cancer.

Using serial sections of frozen and AFA-fixed tissues from 34 breast cancers, we studied the presence of basement membrane material in the areas of elastosis. Various amounts of type IV collagen but not of laminin were demonstrated in areas of periductal elastosis. In some tumors, type IV collagen accumulated beneath the basement membrane. Periductal elastosis in areas of extensive fibrosis showed focal type IV collagen immunoreactivity, indicating remnants of ducts. Interstitial elastosis corresponded with weak type IV collagen reactivity. Each tumor showed type IV collagen immunostaining of the elastotic areas, with various degrees of intensity. Negative crossreactivity of the type IV collagen antibody with elastin was verified in skin biopsies with solar elastosis. Pre-incubation of the antibody with large amounts of elastin demonstrated an identical immunoreactivity. The specificity of the antibody was confirmed by ELISA and by Western blot analysis. To explain the periductal elastosis, we propose the following hypothesis. Excessive production of basement membrane material by the epithelial cells of the ducts leads to formation of a type IV collagen skeleton. This skeleton can act as the matrix for a secondary deposition of elastic material.

Basement Membrane↗
PubMed1990

Intrahepatic lymphatics in the human fetus.

Graphic reconstruction of dilated intrahepatic lymphatics in a 36 week old fetus displayed an anastomosing network of channels with intraluminal valves. Examination of the liver in 42 fetuses between the gestational age of 15 to 40 weeks showed that lymph vessels were visible as early as the 15th week. The detection of intrahepatic lymphatics was not related to the weight of the liver, the underlying cause of death, gender, or congenital anomalies.

Embryonic and Fetal Development↗