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Biomedical subjects

L Andries

Publications and source records attributed to L Andries.

At least 19 recordsLinked to original sources
PubMed1999

Improvement of endocardial and vascular endothelial function on myocardial performance by captopril treatment in postinfarct rat hearts.

Background-Endocardial (EE) and myocardial capillary vascular endothelial (myocap VE) cells have been shown to modulate the contractile characteristics of myocardium in a calcium-dependent manner. We evaluated the endothelial-myocardial interaction in the rat postinfarction myocardial infarction (MI) model and the effects of captopril. Methods and Results-Wistar rats were divided into 4 groups treated for 4 weeks: (1) control; (2) infarcted controls (left anterior coronary artery ligation); (3) infarcted+captopril 2 g/L in drinking water; and (4) infarct+captopril+triton intracoronary injection. Coronary VE function was evaluated by infusion of serotonin in Langendorff preparations (n=31), and the myocardial contractile characteristics were investigated by use of isolated papillary muscles (n=44). Cardiac mRNA for endothelial constitutive nitric oxide synthase (ecNOS) was measured, and its cellular location was evaluated by immunohistochemistry. Serotonin-induced increase in coronary flow was decreased in infarct controls compared with controls (4.6% versus 53.4%, P<0.01) but not in the 2 infarct+captopril groups. Intracoronary triton injection decreased serotonin-induced coronary flow in the infarct+captopril+triton group. All MI groups had decreased total tension in isolated papillary muscles. EE removal by triton immersion decreased total tension in all groups except for infarct controls (3.3 versus 3.2 g/mm(2)). Cardiac ecNOS mRNA decreased in the control infarct group but remained normal in the infarct+captopril group. Conclusions-Chronic postinfarction endothelium-induced coronary vasodilatation is impaired, and both EE and myocap VE dysfunction contribute to myocardial depression. Captopril use prevents these abnormalities and the reduction of cardiac ecNOS mRNA.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Vascular endothelial dysfunction contributes to myocardial depression in ischemia-reperfusion in the rat.

Endocardial and vascular myocardial capillary endothelium has been shown to modulate the contractile characteristics of myocardium by altering myofibrillar affinity for calcium. Although the release of endothelial-derived substances that modify myocardial contractility has been shown to be altered in certain physiologic and pathologic situations, until now no study has evaluated whether the direct modulatory effects of endothelium on its subjacent myocardium were altered in pathologic situations and contributed to loss of contractile function. This study was designed to evaluate whether the direct contractile modulatory effects of endocardial and (or) vascular endothelium were altered and whether these alterations contributed to contractile dysfunction in a model of ischemia-reperfusion. Sixty-two perfused rat hearts as Langendorff preparations were randomized to no intervention, intracoronary Triton X100 injection (to render vascular endothelium dysfunctional), ischemia (30 min)-reperfusion (20 min), and ischemia-reperfusion followed by intracoronary Triton X100 injection. Coronary endothelial-dependent vascular reactivity and vascular smooth muscle reactivity were assessed by serotonin and sodium nitroprusside, respectively. Myocardial damage was assessed by coronary effluent creatine phosphokinase and by morphologic studies. Papillary muscles were then excised and contractile characteristics evaluated at varying extracellular calcium concentration prior to and after endocardial endothelial removal with Triton X100. All three interventions eliminated all coronary vascular response to serotonin but did not modify response to nitroprusside. Creatine phosphokinase values rose only in hearts with ischemia-reperfusion, and only minor morphologic changes occurred, mostly in hearts with ischemia-reperfusion. Papillary muscles from hearts with intracoronary Triton X100 injection had lower contractile indices compared with normal controls (total tension 4.0 vs. 4.6 g/mm2, p < 0.01) and an abbreviation of contraction duration. Increasing extracellular calcium concentration from to 0.7 to 3.25 mM eliminated these differences. Similar but more marked decreases in contractile indices and twitch duration were noted in the two ischemia-reperfusion groups, but consistent with some myocardial damage being present, increasing extracellular calcium concentration to 3.25 or 7 mM did not fully eliminate these differences. In both ischemia-reperfusion groups and the intracoronary Triton X100 group, the relative increase in total tension with increasing extracellular calcium concentrations was similar (35 to 38%) and greater than that of the control group (25%), consistent with dysfunction of vascular endothelium contributing to myocardial dysfunction in the three intervention groups. Endocardial endothelial removal had a similar effect in all four groups, suggesting that dysfunction of endocardial endothelium does not play a role in this model. We conclude that vascular but not endocardial endothelial dysfunction contributes to the myocardial dysfunction that occurs during ischemia-reperfusion injury.

Animals↗
PubMed1996

Vascular-derived myocardial contractile factor: positive myocardial inotropic substance released from medial layer of the canine aorta.

Interactions between the various cell types that make up the cardiovascular system are known to play an important role in maintaining homeostasis. One area about smooth muscle cells that has received little attention, despite the production of a wide variety of mediators by smooth muscle cells, is their effect on myocardial function. In this study, the myocardial contractile effects of four different types of dog aortic strips on rabbit papillary muscles were evaluated. Of these, medial vascular smooth muscle strips most consistently (65% of the time) produced a "vascular-derived contractile factor" (VDCF), which caused a 15% increase in isometric twitch tension and a 24% increase in isotonic twitch shortening with no change in twitch configuration. Endovascular strips with or without intact endothelium and complete aortic rings had less consistent effects. Vascular-derived contractile factor was stable after freezing at -80 degrees C, its activity was not modified by a broad spectrum peptidase, but it was heat-labile. The angiotensin II blocker, losartan, did not modify its effects. However, incubation with indomethacin did reduce, but did not eliminate, the contractile effects of vascular strips. The addition of alpha 1- and beta-blockers did not further modify the effects of VDCF. Endocardial endothelial removal increased the effects of VDCF. No correlation existed between endothelin levels and the contractile effects of vascular strips. It is concluded that VDCF is produced by the medial layer of large vessels but its exact cellular origin is uncertain. These findings expand the ever-increasing understanding of the inter-relationship between the structures that make up the cardiovascular system, and open the door to new studies evaluating the inter-relationship of vessels and myocardium.

Animals↗
PubMed1994

Behaviour of dissociated hypoblast cells on the basal lamina and on extracellular fibrils in the gastrulating chicken embryo.

The spreading behaviour of dissociated hypoblast cells on and besides a band of aligned fibrils associated with the basal lamina of the epiblast was investigated by the use of scanning electron microscopy. A horse-shaped band of aligned fibrils, first demonstrated by Wakely and England (1979), is present during the gastrulation stages of chicken embryos on the ventral side of the epiblast at the cranial and lateral borders of the area pellucida. The basal lamina of the area pellucida situated inside the fibrillar band enables the spreading and probably the locomotion of dissociated cells, which appeared as polarized cells. Numerous cells were also found on the fibrillar band, and these cells lacked distinct lamellae and a polarized shape. Extensions of the cells contacted the extracellular fibrils and, at these sites of contact, the pattern of the fibrils was frequently deformed. From these observations and from previous results emerged the concept that spreading and locomotion of dissociated hypoblast cells, as well as single mesoblast cells and healing hypoblast epithelium, are inhibited by the band of extracellular fibrils, which acts as a physical barrier. The cell biological basis of the mechanism by which extracellular fibrils associated with the basal lamina arrest the migration of hypoblast and mesoblast cells, but guide the migration of primordial germ cells, is discussed.

Animals↗
PubMed1992

Improved endothelial viability of heart valves cryopreserved by a new technique.

The aim of this study was to compare different techniques of aortic valve cryopreservation by studying the viability of the endothelial cells. Viability was assessed by measuring their in vitro prostacyclin (PGI2) production under basal and stimulated conditions. Fresh and cryopreserved porcine valves were incubated at 37 degrees C in tissue culture medium and PGI2 content in the medium was measured every 15 min up to 300 min. Cryopreservation by the older procedure A included 5% fetal calf serum (FCS) in the preservation medium, a plastic box inside a freezing plastic bag, a cooling schedule approximating -2 degrees C/min, a long thawing time and few dilution steps of the cryoprotectant dimethylsulphoxide (DMSO). The newer procedure B differed from A in packaging, freezing and thawing rates and DMSO dilution. Procedure C was similar to B with the exception that FCS was omitted. Leaflets preserved by procedure A produced significantly less prostacyclin as compared to those treated according to procedures B or C. We conclude that minor differences in the cryopreservation method can become critical to endothelial functional viability.

Animals↗
PubMed1992

The arrest of cell migration in the chicken blastoderm: experimental evidence for the involvement of a band of extracellular fibrils associated with the basal lamina.

This article overviews our current knowledge of the occurrence and distribution of oriented extracellular fibrils associated with the basal lamina, and their presumptive role in contact guidance of cells in early embryos. To investigate the role of the band of extracellular fibrils situated at the basal side of the epiblast at the cranial edge of the area pellucida of the chicken blastoderm, we determined the precise location and morphology of the fibrils using TEM and SEM, described the relationship between migrating mesoblast cells and the fibrillar band, and, finally, tested experimentally the behavior of homologous and heterologous tissues in the vicinity of the fibrillar band. The descriptive analysis demonstrated that a horseshoe-shaped, 170 microns-wide band of fibrils occurs at the cranial and lateral edges of the area pellucida and area opaca, the highest density being found in the area pellucida. Migrating mesoblast cells presented a surface morphology that was different from the morphology of cells reaching the fibrils at the lateral edge of the area pellucida. Mesoblast cells never crossed the fibrils, an observation that may explain why during gastrulation, mesoblast cells invade the area opaca only in the caudal region, where no fibrillar band is present. The experimental analysis, which involved transplantation and healing experiments, demonstrated that the arrest of cell migration, that occurred in all cases in the vicinity of the fibrillar band, was correlated with changes in surface morphology suggesting a decreased cell adhesion to the fibrils. From these observations emerged the view that the horseshoe-shaped fibrillar band functions as a barrier inhibiting migration of individual mesoblast cells and expansion of tissue sheets, rather than as an extracellular substrate mediating the oriented guidance of cells. In addition to its inhibitory role in cell migration, the extracellular band may also be regarded as a factor that stabilizes the polarity of the early embryo by determining the cranial and lateral limits between embryonic and extraembryonic tissues.

Animals↗
PubMed1990

A scanning electron-microscopic study of different tympanic grafts.

The surface architecture of dried temporalis fascia autografts and preserved tympanic allografts was investigated by scanning electronmicroscopy. During the storage in formaldehyde-cialit solutions the outer epithelial as well as the inner mucosal layer of tympanic allografts are progressively detached, and finally the lamina propria with outer radial and inner circular fiber arrangement remains. Due to dehydration phenomena irregular "crater-like" defects, surrounded by an amorphous structure, appear in dried fascia autografts. While a real lamina propria graft may induce migration and differentiation of the host's canal wall epithelium into a specific tympanic epithelium, one may imagine epithelial spreading toward the middle ear along the observed defects in dried fascia grafts. This latter observation gives new evidence for the immigration cholesteatoma theory.

Fascia↗
PubMed1988

A scanning electron microscope study of preserved allograft tympanic membranes: a comparison with autogenous grafts, xenografts and the normal eardrum.

Scanning electron microscopy was used to investigate the surface architecture of the human tympanic membrane. The morphology of the eardrum was compared with the surface structures of preserved tympanic membranes (allografts), fresh air-dried temporalis fascia and preserved calf jugular veins (xenografts). The role of the physical structure and the composition of the extracellular matrix in the regeneration of a tympanic graft is discussed.

Humans↗
PubMed1988

Establishment of a typing system for group D streptococci.

Group D streptococci (n = 971, 4037 samples, 139 patients) were isolated from two intensive care units. Differentiation and typing revealed 6 species, 25 phage types, and 85 enterococcinotypes. Distribution of species showed strong differences especially concerning Enterococcus faecium which was rarely isolated from extraintestinal sites (5.9%). Phage typing was species specific and discriminated Enterococcus faecalis (n = 703 typable isolates, 19 phage types) and the other group D streptococci (n = 63 typable isolates, 6 phage types). Based on the production of enterococcines (15 indicator strains used) the isolates could be classified into 6 groups, one of which was further subdivided into 3 subgroups. Enterococcus faecalis ssp. liquefaciens (n = 618), phage type V6b (n = 596), and enterococcine group IVc (n = 568) were most common. The combined use of markers resulted in 187 combinations, which demonstrated the valuable properties of the system.

Bacteriocins↗
PubMed1987

Combined use of phage typing, enterococcinotyping and species differentiation of group D streptococci as an effective epidemiological tool.

Ninety-five group D streptococcal isolates from the feces of 95 healthy persons were compared with 157 group D streptococcal isolates from 38 patients of the surgical intensive care unit (sICU). The typing systems consisted of phage typing, enterococcinotyping and species differentiation. Strains isolated from fecal specimens showed high individuality (66 combination types) whereas strains from the sICU revealed strongly uniform types (32 combination types, three types comprised 83 isolates, i.e. 52.8%). Endogenous colonization was demonstrated by isolation of strains from different locations (throat, trachea, wounds, blood, urine, drains, catheters, and vaginal swabs) from the same patient, and routes of transmission of the same strains to several patients were traced. The combination of three systems revealed a good discrimination between isolates of fecal and extrafecal specimens. The investigation detected highly preferred types in strains of extrafecal origin which were rarely isolated from fecal specimens. This may indicate that only strains with special characters preferably were able to colonize extraintestinal sites.

Bacteriophage Typing↗
PubMed1987

Differential distribution of cell protrusions on the ventral surface of the deep layer in gastrulating quail and chick embryos.

The ventral surface of the deep layer of gastrulating quail and chick embryos was examined using scanning electron microscopy. On the basis of cell protrusions, three or four different cell types were recognized. Cells covered with microplicae were found in the caudal region of the germ and as a narrow band extending along the lateral and anterior borders of the area pellucida. Cells covered with microvilli were found in a horseshoe-shaped zone in the anterior part of the germ. Beneath the rostral end of the primitive streak, the flattened deep-layer cells exhibited intercellular ridges and few microvilli. This area was surrounded by cells that usually had extended microvilli. The pattern of these cell types is discussed in relation to the formation of the different tissues that compose the deep layer in gastrulating embryos.

Animals↗
PubMed1986

Microinjection of glycosaminoglycan-degrading enzymes in the chicken blastoderm. An ultrastructural study.

The relationship between the presence of glycosaminoglycans (GAGs) and the morphology of the middle layer or mesoblast was examined by performing transmission electron microscopy of chicken blastoderms microinjected with GAG-degrading enzymes. The controls included microinjections with saline or trypsin, as well as solid-phase assays for proteolytic activity in commercially available GAG-degrading preparations. The results indicate that, in normal as well as in saline-injected blastoderms, middle-layer cells are rounded or cuboidal in shape, and are linked to each other by small intercellular junctions in the primitive-streak region. As they migrate laterally along the basal lamina, they appear as typical mesenchymal cells, being separated by large intercellular spaces and covered by cell processes. The removal of hyaluronate (by the microinjection of hyaluronidases) led to compaction of the middle-layer cells in the area lateral to the primitive streak. These cells lost their mesenchymal aspect and retracted their processes, and intercellular junctions were observed. The presence of proteolytic activity in the enzyme preparations did not interfere with the results. On the basis of the results obtained using this microinjection technique, we were able to confirm at the ultrastructural level that hyaluronate, due to its space-creating properties, promotes the detachment of ingressed primitive-streak cells and preserves the mesenchymal aspect of the middle layer during the lateral migration of single cells along the basal lamina. Whether the presence of hyaluronate is necessary to allow positioning of the mesoblast could not be inferred using our experimental procedure. We present evidence that this molecule, as well as having physicochemical properties, is also involved in the modulation of tissue interactions during gastrulation.

Animals↗
PubMed1986

Tympanic grafts. An ultrastructural study.

Scanning electron microscopy (SEM) was used to investigate the surface architecture of human tympanic membranes. The morphology of the normal eardrum was compared with the surface structure of preserved tympanic membrane (allograft), fresh air-dried fascia temporalis and preserved calf jugular vein (xenograft). The role of the physical structure and composition of the extra-cellular matrix in the restoration of a tympanic graft is discussed.

Animals↗
PubMed1985

Inhibition of cell spreading on the band of extracellular fibres in early chick and quail embryos.

The ventral surface of the upper layer shows a band of extracellular fibrils around the anterior and lateral border of the area pellucida during gastrulation of the chick embryo. Using scanning electron microscopy, we found that this disposition is correlated with the motility of the middle-layer cells of gastrulating chick and quail embryos. Outside the fibrous band, single middle-layer cells and a sheet of mesoblast cells were spread out and possessed lamellae. Single cells on the fibrous band did not form lamellae. The same cell behaviour was obtained with the explants of deep layer on the fibrous band. The fibrous band is assumed to operate as a barrier that inhibits cell motility during gastrulation.

Animals↗
PubMed1985

Cell junctions and locomotion of the blastoderm edge in gastrulating chick and quail embryos.

The blastoderm edge migrates by the active locomotion of a multilayer of epithelial cells, the so-called margin of overgrowth (MO), that uses the vitelline membrane as its substratum. The structural unity formed by the margin of overgrowth cells and their rapid migration suggest coordination of locomotion between individual cells. Using transmission electron microscopy of thin sections and freeze-fracture, we attempted to determine if the pattern of junctions of the migrating margin of overgrowth is related to the suggested cell--cell cooperation between individual cells in this region. In the leading edge there are large areas of closely apposed cell membranes. Incipient desmosomes and small gap junctions were observed. Tight junctions consisted of isolated strands or isolated networks of tight-junctional strands. In the proximal part of the margin of overgrowth the size of the gap junctions increased and the desmosomes were fully developed. Tight-junctional strands were either isolated or arranged into an isolated network. A broad belt of tight junctions was observed at the transition between margin of overgrowth and non-marginal cells. The distribution of the junctional elements in the MO suggests that junctions contribute to the maintenance of the structural and functional organization of the margin of overgrowth. Furthermore, the spatial distribution of the junctions might give information about the mechanism of locomotion of the margin of overgrowth.

Animals↗
PubMed1985

Scanning electron microscopical analysis of the acute and chronic effects of intra-cochlear electrode implantation.

Scanning electron microscopy was used to study the acute histopathological effects immediately after surgical implantation of a 2-channel electrode, and the chronic effects after long-term placement of the perscalar implant. This study with cats shows that an atraumatic implantation can be achieved and that the peripheral neural structures were retained although the hair cells degenerated and the spatial organization of the supporting cells was slightly changed. The population of hair cells outside the region of the implanted electrode was not affected.

Animals↗
PubMed1985

[Typing of Streptococcus faecalis and Streptococcus faecium strains with bacteriophages].

With a set of 17 bacteriophages specific for Streptococcus faecalis and a set of 7 bacteriophages specific for Streptococcus faecium 441 strains of S. faecalis and 53 strains of S. faecium were typed. The species identification was done by means of the API 20 STREP system. For S. faecalis 22 and for S. faecium 12 lysotypes were found. Among S. faecalis strains lysotype V6b was most common (27%), followed by the lysotypes XV (9,5%), XIII1 (7%), II1 (5,7%), and I1 (4,3%). These 5 lysotypes comprised 54% of all 441 strains. 21% of the strains of S. faecalis and 6 from 53 strains of S. faecium were untypable. Strains of S. faecium were most frequently isolated from faeces and in rare cases from urine. To the contrary 50% of the S. faecalis strains were isolated from urine. There was no correlation between special lysotypes and age of the patients or the source of specimen. The results of phage typing of several strains from one patient, and especially of strains from mothers and their newborns suggest the usefulness of the typing system to clarify epidemiological questions.

Adolescent↗