Biomedical subjects

L de Saint-Georges

Publications and source records attributed to L de Saint-Georges.

7 recordsLinked to original sources

PubMed1992

The microcirculation of bone and marrow in the diaphysis of the rat hemopoietic long bones.

The nature of the microcirculation of the diaphyseal portion of long bones and the adjacent bone marrow is poorly understood. The purpose of this study was to describe the blood supply in the diaphyseal cortex and the relationship of the bone vascular circulation to that of the bone marrow in the growing rat. India ink-gelatin was infused in the arterial system of 3-month-old rats and the vascularization was determined from histological sections. In some studies the periosteal circulation was blocked but the nutrient and metaphyseal arteriole systems were left intact. In the growing rat, most of the vascular flow appears to be centripetally through the diaphyseal cortex and this appears to be the primary blood supply for the adjacent bone marrow. The India ink traversed the cortex and entered the marrow through osteal canals at the endocortical surface. At the marrow-endocortical bone surface interface, ink exiting from the osteal canals filled the adjacent marrow sinusoids in what appeared as "bush-like" structures. From the bone marrow the ink appeared to drain into the central vein. Some arterioles from the nutrient system were found to penetrate the inner two thirds of the cortical bone and then re-enter the bone marrow. The centripetal flow of blood and the importance of the cortical flow for perfusion of the hemopoietic tissue was further documented when periosteal flow was obstructed. In this situation, the cortical bone and adjacent bone marrow were not perfused while the nutrient system and central vein were filled with ink.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Ultrastructural features of osteoclasts in situ.

The morphology of in situ osteoclasts on endocortical surfaces of the femoral midshaft was examined by scanning electron microscopy. Mice were perfusion fixed and bone marrow plugs were flushed out of femoral diaphyseal cylinders. The bones were split longitudinally and the endocortical surfaces examined. This method left on the bone surface most of the endosteal cells in their natural, in situ shape and position. Most of the bone surface was lined by contiguous bone lining cells covering resting bone surfaces, making a clear physical barrier between the bone and marrow compartments. On resorption surfaces, which were characterized by excavation cavities, osteoclasts were very polymorphic and spread on the bone surface, extending large pseudopods. The in vivo morphology of individual osteoclasts appears somewhat similar to that described by other investigators on calvaria surfaces and for isolated osteoclasts adherent to artificial substrates. In the resorption domains, osteoclasts appeared to be connected with adjacent osteoclasts, suggesting that the cells form a functional syncytium in resorption areas.

Animals↗

PubMed1989

Bone lining cells: structure and function.

Bone lining cells (BLC's) cover inactive (nonremodeling) bone surfaces, particularly evident in the adult skeleton. BLC's are thinly extended over bone surfaces, have flat or slightly ovoid nuclei, connect to other BLC's via gap junctions, and send cell processes into surface canaliculi. BLC's can be induced to proliferate and differentiate into osteogenic cells and may represent a source of "determined" osteogenic precursors. BLC's and other cells of the endosteal tissues may be an integral part of the marrow stromal system and have important functions in hematopoiesis, perhaps by controlling the inductive microenvironment. Because activation of bone remodeling occurs on inactive bone surfaces, BLC's may be involved in the propagation of the activation signal that initiates bone resorption and bone remodeling. Evidence also suggests that BLC's are important in the maintenance of the bone fluids and the fluxes of ions between the bone fluid and interstitial fluid compartments for mineral homeostasis.

Animals↗

PubMed1988

Mineralization of adult mouse bone marrow in vitro.

Murine adult bone marrow exhibits mineralizing capacity in vitro as is demonstrated by the new in vitro assay we report here. In less than 2 weeks after the onset of the cultures, mineralization is obtained in more than 80% of the marrow cultures. Moreover, morphological studies reveal that during incubation phenotypic changes related to osteogenic differentiation occur at the extracellular matrix as well within cell populations. Well banded collagen is synthesized. Matrix vesicles and needles of hydroxy-apatite crystals are observed via transmission electron microscopy. Osteoblast-like cells are present with membrane-associated alkaline phosphatase activity. The mineralization is specific for cultured bone marrow and is not observed in cultured spleen fragments as is shown via 85Sr uptake, calcein uptake and histomorphology. No inducing agent is added to the tissue culture medium except for 10% fetal calf serum, beta-glycerophosphate (10(-2) M) and ascorbic acid. However, the prerequisite for obtaining mineralization is the three-dimensional structure of the marrow in culture. The in vitro organ culture we developed may provide the opportunity to identify which marrow cells have osteogenic potential and to investigate the mechanisms triggering differentiation towards osteogenesis.

Animals↗

PubMed1988

Response of mouse lung air-blood barrier to X-irradiation: ultrastructural and stereological analysis.

Male mice of the Balb/c strain were exposed, at an age of three months, to a single dose of 10 or 20 Gy on the right hemithorax. At 3, 4, 6, 9 and 12 months after exposure, lungs were processed for electron microscopy following a standardized procedure in order to allow stereological analysis. By this method, the arithmetical mean thickness and, the air-blood barrier mean thickness in the lung parenchyma was shown to increase quickly with time by oedemization and fibrinization of the septal space. The ratio endothelium/epithelium surfaces (SI/SE) gradually decreased by reduction of both surfaces but this was more marked for Si. The endothelium and epithelium were both highly damaged. Quantitative results indicate that damage to the epithelial cells and mainly to type II, appear at the same time as damage to the endothelium. From the time lapse quantitation it is not possible to determine which one plays the predominant role in the radiation pneumonitis. The strong reaction of the basement membrane and mainly of the interstitial cells could play a decisive role in the evolution of the illness.

Air↗

PubMed1986

Genome organisation of the FBR-osteosarcoma virus complex: identification of a subgenomic fos-specific message.

The FBR murine virus complex together with the FBJ murine virus complex are known to be bone tumor inducers in newborn mice. Both transforming viruses have transduced c-proto-fos-derived sequences in their genome. FBR-MuSV was molecularly cloned as a biologically active 10-kbp EcoRI fragment from non-productively transformed rat embryo fibroblasts into Charon phage 4A (lambda MOL503) and subsequently subcloned in plasmid pBR322 (pMOL503). Its natural associated helper FBR-MuLV, excized as an internal 8.2-kbp PstI proviral DNA fragment from chronically infected NIH/3T3 cells, was cloned into the unique PstI site of pBR322. Comparative analysis of the restriction maps of FBR-MuSV and FBR-MuLV together with the electron microscopic analysis of heteroduplex DNA molecules formed between both molecular clones suggested that FBR-MuLV is the parental virus of FBR-MuSV. fos- and fox-specific DNA hybridisation probes identified a genomic sized 3.3-kb mRNA and a subgenomic 2.2-kb messenger RNA. Using a 5'-gag hybridisation probe, only the genomic 3.3-kb RNA molecule was detected, demonstrating that a donor splice site is present upstream of the gag sequences and used to generate the fos-specific 2.2-kb subgenomic mRNA.

Animals↗

PubMed1978

[Lead toxicity in mice embryos].

Administration to female mice before coïtus and to pregnant female mice of an alimentation containing 0.1 p. 100 lead acetate imparied the fertility. Studies on the changes of the ultrastructure of the embryos during the first stages of development do not allow to detect lesions unless on day 7 where lead inclusions are detected in the mitochondria.

Animals↗