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Biomedical subjects

M E LeFevre

Publications and source records attributed to M E LeFevre.

At least 19 recordsLinked to original sources
PubMed1989

Intestinal uptake of fluorescent microspheres in young and aged mice.

Rhodamine B-labeled synthetic latex particles (microspheres), 1.8 micron in diameter, were administered by gavage 5 days per week to young (24 days) and aged (18 months) mice. After 25 days (19 gavages), the particles were assayed in solubilized tissues by depositing them on filters and counting under fluorescence microscopy. Aged mice exhibited significantly more fluorescent particle accumulation in Peyer's patches but significantly less in lungs than young mice. Mesenteric lymph nodes and Peyer's patch-free intestinal segments contained measurable latex, but differences between young and aged animals were not significant. Liver contained only trace amounts of latex, and spleen and kidney were latex free in both young and aged animals. Nonquantitative observations on KOH-glycerol-cleared whole Peyer's patches and slices of liver, lung, and mesenteric lymph node were similar.

Aging↗
PubMed1986

Distribution of label after intragastric administration of 7Be-labeled carbon to weanling and aged mice.

Single doses of 7Be-labeled carbon particles prepared by proton bombardment of carbon black were administered by gavage to weanling (4 weeks) and aged (18 months) mice. Body distribution of 7Be radioactivity was determined 4 hr and 1, 2, 5, and 14 days later. The results were compared with those obtained after administration of a solution of 7BeCl2. 7Be radioactivity in nonintestinal tissues was 17-58 times greater in mice gavaged with the soluble salt than in those gavaged with the particles, indicating that particle-bound 7Be was well confined to the gastrointestinal tract. Upper limits of the amount of labeled carbon remaining in intestinal Peyer's patches were as follows: 1 day: weanling, 1.8 X 10(-3)%, old, 5.5 X 10(-3)%; 15 days: weanling, 3.3 X 10(-5)%, old, 8.4 X 10(-5)%. The particles are potentially useful as models for diesel emissions or other particulate pollutants.

Age Factors↗
PubMed1985

Particles and macrophages in murine Peyer's patches.

Mice were given 1% suspensions of 5 insoluble particles (chrysotile asbestos, quartz, carmine, carbon, and iron oxide) in drinking water for 3 months. The particles were subsequently sought in intestinal Peyer's patches by light microscopy. Carbon and iron oxide particles were visible in Peyer's patch macrophages, particularly in the subepithelial region, but the other particles could not be detected. The findings suggest that particle surface properties as well as particle size govern accumulation in Peyer's patches. The cytochemistry of subepithelial, mid-dome, tingible-body, and serosal macrophages of control mice indicated diversity of macrophages within the patch. Macrophages of asbestos-fed mice contained more lysosomes than macrophages of controls. Macrophage abundance in the dome apex was not significantly altered by asbestos ingestion. The other particles did not produce detectable alterations in macrophage morphology.

Animals↗
PubMed1983

Ultrastructure of macrophages of the murine Peyer's patch dome.

The ultrastructure of macrophages located in the dome of murine Peyer's patches was examined by transmission electron microscopy. Aggregates of carbon particles as well as numerous other phagocytic and lysosomal inclusions were consistently observed in dome macrophages of carbon-fed mice. Macrophages of both particle-fed and control mice exhibited morphological features of activation. Degenerating macrophages were observed, and evidence is presented that their disintegration involves invasion by other cells. The morphological findings are in accordance with other evidence that the Peyer's patches receive an influx of material from the intestinal lumen. The potential importance of macrophages in the initiation of intestinal inflammations is emphasized.

Animals↗
PubMed1982

Frequency of black pigment in livers and spleens of coal workers: correlation with pulmonary pathology and occupational information.

Histologic sections of liver and spleen from 99 retired coal workers and nine non-coal workers were obtained at autopsy and scored for black pigment. Pigment was minimal in the non-coal workers, with the exception of one person with silicosis. Moderate or heavy pigment was seen in 10.4 per cent of liver sections and 19.5 per cent of spleen sections from coal workers. The extrapulmonary pigment was not associated with any pathologic tissue response. Information on pulmonary pathology and occupational exposure to dust was available for most workers. Highly significant positive correlation was found between the severity of pneumoconiosis and the black pigment score in both liver and spleen; the correlation between emphysema and pigment score was lower, but still significant for liver. Significant positive correlations were found between years spent underground, years of retirement, and age at death versus pigment scores. Significant negative correlation was found between smoking and pigment. The positive association of extrapulmonary pigment with age at death, years of underground mining, and severity of pneumoconiosis suggests that cumulative lifetime exposure to coal mine dust may be the most important factor in the release of dust into the general circulation.

Coal Mining↗
PubMed1981

Demonstration of particulate accumulations in solid tissue.

We describe a histological clearing procedure involving partial tissue hydrolysis by pancreatin and demonstrate its application. Changes in distribution of 5.7-micrometers latex particles in mouse liver and heart muscle 6 months after i.v. latex injection were quantitated. The method is useful for studied of long-term redistribution of particles in vivo and for locating large, infrequent particles which are difficult to find by ordinary tissue-sectioning technique.

Animals↗
PubMed1980

Intestinal barrier to large particulates in mice.

Intestinal barrier function in mice was assessed after acute or chronic oral administration of 15.8- and 5.7-micron synthetic spherical particles. The results failed to confirm previous reports that ingested particles rapidly appear in blood. Furthermore, 15.8-micron particles did not accumulate in intestinal Peyer's patches, mesenteric lymph nodes, or other organs of the reticuloendothelial system, even after the maximum dosage of 8 X 10(6) particles per day for 60 d. However, the 5.7-micron particles were demonstrated in Peyer's patches, mesenteric lymph nodes, and lungs after the maximum dosage of 4.5 X 10(8) particles per day for 60 d. At 77 d after the termination of ingestion, 5.7-micron particles were still present in these tissues. The 5.7-micron particles were not found in spleen; retention in liver was equivocal. The site of uptake of particles capable of penetrating the intestinal mucosa appears to be the Peyer's patches. It is suggested that most absorbed particles are sequestered in Peyer's patch macrophages. Particles that escape sequestration are transported by lymph rather than by portal blood. The findings indicate that hazards associated with intestinal uptake of large (> 5 micron) particulates exist, but that the frequency of such penetration is still unclear.

Animals↗
PubMed1978

Structure, function, and long-term maintenance of the isolated turtle colon.

We describe the 5-day maintenance of sacs of turtle colonic mucosa in enriched bathing solutions. The mean maximum transepithelial potential difference (PD) developed by the sacs in Ringer solution enriched with tissue-culture medium and gassed with 95% air-5% CO2 was 126 mV at 24 hours. Lower values were observed in other solutions. The PD of 24-hour sacs was partially or totally inhibited by ouabain, replacement of Na by choline in mucosal bathing fluids, or removal of Ca from serosal bathing fluids. The sacs transported Na in excess of H2O forming a dilute mucosal solution. The response of four different sac preparations (normally oriented or everted, and stripped normally oriented or everted) to long incubation were compared. Stripped normally oriented tissue developed the highest PD and maintained the lowest water content. The morphology of fresh and long-incubated tissue was examined. This investigation demonstrates that the turtle colon can be maintained in vitro for long periods, and it provides information on the morphology and physiology of this tissue.

Animals↗
PubMed1976

Effects of peptide hormone structure on H+ secretion by Necturus gastric mucosa.

The actions of human synthetic gastrin I(G), the C-terminal tetrapeptide of gastrin (T), and the C-terminal octapeptide of cholecystokinin (OP) on acid secretion and transepithelial potential difference (PD) of the isolated Necturus gastric mucosa were determined. All three peptides induced H+ secretion, but the maximum H+ output was less with OP than with G or T. G and OP produced their maximum H+ output at lower molar concentrations than T. G- and OP-stimulated secretion was long sustained, but T-stimulated secretion rapidly returned to basal levels. T- and G-stimulated secretion was partially inhibited by the addition of OP. Evidence is presented that T rapidly disappears from solutions exposed to gastric mucosa, whereas G does not. Washing sensitized the mucosa to subsequent addition of T. The results suggest that the action of the common C-terminal tetrapeptide of G, T, and OP is modified by the preceding amino acid sequences, and that T, the smallest of the three peptides, is rapidly degraded by gastric tissue in vitro. The implications of the work for the study of gastrointestinal hormone structure-function relationships in isolated tissue preparations are discussed.

Animals↗