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Biomedical subjects

N Buyssens

Publications and source records attributed to N Buyssens.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1988

Desmin-positive stellate cells associated with angiogenesis in a tumour and non-tumour system.

The angiogenesis induced after implantation of fragments of the Walker 256 carcinoma was compared with the angiogenesis following implantation of different amounts of Indian ink. Morphologically and chronologically the tumour system showed no difference from the Indian ink system, provided sufficient amounts of ink were implanted. Both systems were characterized by significant macrophage infiltration. The vascular development, which was clearly concentrated in a dense rim around the tumour, remained present when the tumour enlarged, suggesting an acquisition of vasculature by the tumour through vessel incorporation and not vessel ingrowth. Initially, scattered desmin-positive cells, in contact or encircled by collagen IV, were found in the developing angiogenic rim. Later many desmin-positive cells were found around vessels and could be identified by electron microscopy as pericytes. They exhibited close local contacts with endothelial cells. After incorporation of the peritumour vascular rim into the tumour the number of pericytes decreased and their shape became flattened and elongated.

Animals↗
PubMed1988

Nevus cell maturation or atrophy?

Nevus cells show considerable variation in their appearance, depending on their localization in epidermis, upper dermis, or deep dermis. The difference in appearance of nevus cells when located superficially or in the deep dermis has been referred to as nevus cell "maturation." The aim of this study is to objectify morphological differences between nevus cells in epidermis, upper dermis, and deep dermis by means of a morphometric study at light- and electron microscopic levels. The results show that there is a decrease in number and size of all structures except for mitochondria and microfilaments. These findings are consistent with atrophy. The concepts of maturation, differentiation, and atrophy are also discussed.

Atrophy↗
PubMed1988

Malnutrition and the heart: a microscopic analysis.

The effect of starvation on heart morphology was studied in the rat after total caloric deprivation. Morphometric analysis in subendocardial and subepicardial regions in the left and right ventricle was performed before and after starvation. A progressive fall in body weight was noted together with a biphasic change in ventricular weight. The ratio heart/body weight showed a continuous rise initially but stabilized at high levels in the later stage of starvation (p less than or equal to 0.005). The observed changes were analogous in the right and left ventricle. After starvation a significant increase in myocyte volume fraction was noted (p less than or equal to 0.01), but no regional differences were observed with respect to subendocardial-subepicardial and right-left ventricular zone comparison. The change in the non-myocyte fraction is situated in the vascular space and connective tissue. The volume fraction of non-capillary interstitial connective tissue, however, is significantly greater in the right ventricle than in the left (p less than or equal to 0.005). We conclude that in total starvation, after an initial rapid decline in heart weight, the heart is relatively spared. This leads to a rising heart/body weight ratio, until the later stage of malnutrition when the heart undergoes a hypotrophy to the same extent as other organs. This hypotrophy gives rise to a relative increase in myocyte volume fraction and a parallel decrease in capillary volume without major changes in the interstitial non-capillary connective tissue compartment.

Animals↗
PubMed1987

Factors influencing the subjective grading of bladder cancer.

In order to study factors which influence the subjective grading of bladder cancers the hypothesis of an ideal examination system was tested. The subjective results were compared with morphometry on the nuclear size of non selected cells. The results show that with precise criteria, with examination of the total section surface field by field and with recording of a grading per field a better interobserver consistency can be obtained. Morphometry demonstrates the heterogeneity and the Gaussian distribution of nuclear sizes in normal and diseased urothelium. It shows that subjective grading is influenced by a small number of larger nuclei and that even in grade 3 tumours 50% of the nuclei have sizes within normal values.

Cell Nucleus↗
PubMed1987

5-Azacytidine and 5-aza-2'-deoxycytidine behave as different antineoplastic agents in B16 melanoma.

The antiproliferative effects of 5-azacytidine (acaCyd) and 5-aza-2'-deoxycytidine (azadCyd) were studied in murine B16 melanoma and a series of B16 melanoma derived mutant strains with selective resistances to the respective drugs. The in vitro cytotoxicities of azaCyd and azadCyd on B16 wild type, expressed in terms of IC50 values, were found to be 5 microM and 0.2 microM, respectively. The in vitro cytotoxicity of both drugs was dependent on the duration of exposure. Uridine and cytidine were able to reverse the in vitro cytotoxicity of azaCyd, but not of azadCyd. Conversely, 2'-deoxycytidine was able to reverse the cytotoxic effect of azadCyd but not of azaCyd. Thymidine and 2'-deoxyuridine had no detectable effects on the in vitro cytotoxicity of either azaCyd or azadCyd. B16 melanoma mutant strains that were selected for resistance to azaCyd showed no cross-resistance to azadCyd, cytosine arabinoside or the fluorinated pyrimidine analogues FUrd, FCyd, FdUrd and FdCyd. Mutant strains that were selected for resistance to azadCyd showed no cross-resistance to azaCyd or fluorinated pyrimidine analogs, but only to cytosine arabinoside. The combined data suggest that azaCyd and azadCyd follow different routes of intracellular metabolic activation and exert their cytotoxic activity via different intracellular targets.

Animals↗