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Biomedical subjects

R Sullivan

Publications and source records attributed to R Sullivan.

At least 163 records · Page 9Linked to original sources
PubMed1980

Aplastic anemia: lack of inhibitory effect of bone marrow lymphocytes on in vitro granulopoiesis.

Prompted by previous reports that in certain patients with aplastic anemia, cell-mediated autoimmune suppression of myeloid stem cell proliferation may be demonstrable in vitro, we studied the effects of bone marrow lymphocytes from 18 patients with myeloid aplasia on the proliferation of committed granulocytic-monocytic progenitor cells (CFU-C). When assayed in soft agar cultures, marrow suspensions from 10 patients with aplastic anemia contained significantly fewer viable CFU-C than similar cell preparations from control subjects. To deplete marrow cell suspensions of lymphocytes, we employed rabbit anti-human thymocyte serum (ATS), which after multiple adsorptions exhibited marked cytotoxicity for human B and T lymphocytes but had negligible effect on normal CFU-C proliferation. Preincubation of marrow samples from 12 patients with ATS and complement resulted in no inhibition or enhancement of CFU-C growth. In further experiments, marrow cells from 8 patients were incubated with marrow from control subjects prior to CFU-C culture. No suppression of donor CFU-C proliferation was observed in any of these studies, and in 4 cocultures, mixture of the 2 marrow suspensions resulted in stimulation of CFU-C growth. Using these assays, we detected no evidence of cell-mediated inhibition of CFU-C proliferation in any of the 18 patients that we evaluated. Our data support the conclusion that in the majority of patients with aplastic anemia, an absolute deficiency of hemopoietic stem cells is present within the marrow that does not appear to be effected or sustained by suppressor lymphocytes. Whether the reduction of viable stem cells is the cause or the consequence of the process that leads to marrow failure remains unknown.

Anemia, Aplastic↗
PubMed1980

Fractionation of human bone marrow cell suspensions in nylon fiber columns: an efficient method for the removal of cells that produce colony stimulating factor (CSF).

In this report, we describe an efficient technique for the extraction of CSF-producing cells from human marrow suspensions. Prior to plating in agar cultures, we incubated buoyant human marrow cells for 45 min in columns packed with nylon fiber or subjected the cells to two one-hour incubations in glass petri dishes. Recoveries of total cells, differential marrow elements, and committed granulocyte-monocyte progenitor cells (CFUc) were similar after each separative procedure. However, spontaneous CFUc proliferation was more effectively eliminated when cells were fractionated in nylon fiber columns. After the removal of cells which were adherent to glass, spontaneous CFUc proliferation in cultures containing no exogenous CSF accounted for 2.1% of total CFUc at a plating concentration of 10(5) cells/ml and 7.8% at a concentration of 3 X 10(5) cells/ml. After the fractionation of marrow cell suspensions in nylon fiber columns, spontaneous CFUc growth was completely obliterated at a plating concentration of 10(5) cells/ml, and at a concentration of 3 X 10(5) cells/ml accounted for only 0.09% of total CFUc. Further experiments were undertaken which demonstrated that buoyant marrow cells after incubation in nylon fiber columns may be employed to assay CSF in extremely dilute concentrations. Because of the simplicity and efficiency of this procedure, nylon fiber chromatography appears to be a highly useful technique for the rapid semi-purification of marrow suspensions for use in the assay of human CSF.

Bone Marrow↗
PubMed1979

Stem cell migration induced by erythropoietin or haemolytic anaemia: the effects of actinomycin and endotoxin contamination of erythropoietin preparations.

The injection of erythropoietin or the induction of anaemia with phenylhydrazine leads to changes in murine pluripotent and granulocyte-macrophage stem cells indicating migration from marrow to spleen. In order to evaluate the interrelationship between erythroid differentiation and stem cell migration we have selectively suppressed erythroid differentiation with actinomycin D. Anaemia or EP injection resulted in stem cell changes consistent with migration; actinomycin blocked these changes in anaemic but not EP injected mice while blocking erythropoiesis in both groups. The erythropoietin contained from 0.01 to 1000 microgram/ml of endotoxin as defined by the limulus test; it decreased marrow erythropoiesis and stimulated marrow granulopoiesis. Adsorption of the erythropoietin preparation with limulus lysate removed endotoxin without decreasing erythropoietin activity. Adsorbed erythropoietin stimulated erythropoiesis and not granulopoiesis, and stem cell changes induced by its administration were largely blocked by actinomycin, suggesting that endotoxin in the non-adsorbed erythropoietin caused the actinomycin resistant stem cell changes. The observation that actinomycin blocks both erythroid differentiation and stem cell migration suggests that these two physiologic events are closely linked. The effects of injected erythropoietin on murine haemopoietic stem cells may, to a significant extent, be secondary to the presence of endotoxin in the erythropoietin preparations.

Anemia, Hemolytic↗
PubMed1979

The use of stem cell assays to monitor the proliferative potential of bone marrow cells.

A number of assays exist for hematopoietic stem cells in both humans and mice, but the appropriate stem cell assay for the repopulating potential of human marrow is not clear. Two murine models suggest that these assays may not always predict marrow proliferative potential. In vivo diffusion chamber culture growth of CD1 marrow depleted of pluripotent stem cells (CFU-S) by exposure to mouse-brain antisera plus complement was equivalent to or greater than that of normal serum treated control marrow. Furthermore, CF1 mice repeatedly injected with endotoxin had markedly stimulated granulopoiesis with increases in the number of marrow CFU-S and the % in S phase but no changes in the number or proliferative status of marrow CFU-C. However, inbred BDF1 mice chronically injected with endotoxin although also showing striking increases in granulopoiesis had no significant alteration in their marrow CFU-S or CFU-C number or cell cycle status relative to saline injected controls. Both models present examples where conventional stem cell assays do not provide insight into marrow cell production and suggest that in vitro clonal assays of human marrow cells may not always predict for the potential of marrow to repopulate a human transplant recipient.

Animals↗
PubMed1979

Contamination of erythropoietin by endotoxin: in vivo and in vitro effects on murine erythropoiesis.

Endotoxin was detected in all erythropoietin preparations tested and was removed from four lots, without loss of erythropoietic activity, by adsorption with limulus amebocyte lysate. Comparison of adsorbed (endotoxin-depleted) and nonadsorbed (endotoxin-containing) erythropoietin preparations demonstrated significant inhibition of CFU-e and BFU-e in vitro by nonadsorbed erythropoietin at concentrations higher than 0.25 U/ml and 2.0 U/ml, respectively. CFU-e and BFU-e were inhibited significantly by readdition in vitro of 10(-5)-10(-3) mug of endotoxin per unit of limulus-adsorbed erythropoietin. Administration of saline or 6 U of nonadsorbed or adsorbed erythropoietin twice a day for 4 days of CF1 mice resulted in reticulocyte counts of 2.1%, 9.9%, and 15.9%, respectively. Nonadsorbed erythropoietin resulted in a 29% decrease in erythropoiesis, a 42% decrease in CFU-e, and a 16% increase in granulopoiesis in the marrow, whereas adsorbed erythropoietin caused a 28% increase in erythropoiesis, no significant change in CFU-e and a 19% decrease in granulopoiesis in the marrow. Both preparations resulted in marked increases in splenic erythropoiesis and granulopoiesis. The effects of adsorbed erythropoietin are similar to those produced following stimulation of hematopoiesis by endogenous erythropoietin. Hemopoietic changes induced by nonadsorbed erythropoietin in vivo and in vitro are affected substantially by contamination of the erythropoietin preparations with endotoxin.

Adsorption↗
PubMed1978

Inhibition of normal murine hematopoiesis by leukemic cells.

Inhibition of normal mouse hemopoietic stem cells by leukemic cells (C1498) was observed with use of in vitro agar and in vivo diffusion-chamber cultures. The C1498 cells were unresponsive to colony-stimulating activity, and, above a critical threshold, they inhibited normal granulocyte progenitors in agar culture. C1498 cells added to normal marrow in diffusion chambers progressively reduced granulocyte progenitors. The larger, more rapidly growing, C1498 cells showed the most inhibitory effect. Transmembrane culture of C1498 cells adjacent to normal marrow in double diffusion chambers for five to 14 days led to reduction of recovery of granulocyte progenitors (72 +/- 7 per cent of control) and pluripotent stem cells (45 +/- 7 per cent of control) from the normal marrow chambers. These results indicate that leukemic mouse cells inhibit normal mouse-marrow stem cells by releasing a diffusible substance, and this inhibition occurs primarily at the level of the pluripotent stem cell.

Animals↗
PubMed1978

Effects of actinomycin D in vivo on murine erythroid stem cells.

Low-dose actinomycin D (Acto) selectively suppresses murine erythropoiesis without decreasing erythropoietin (Ep) production. We used the plasma clot system to determine the stage of erythroid differentiation at which this inhibition occurs. Late erythroid precursors, CFU-E, and less differentiated committed erythroid stem cells, BFU-E, were assayed in CF1 mice given Acto 75-82 microgram/kg/day or saline subcutaneously for 5 days. We also assayed pluripotent (CFU-S) and committed granulocyte-monocyte (CFU-C) stem cells. Reticulocytes and marrow and spleen nucleated erythroid precursors were decreased by 99% in the Acto-treated mice; tibial marrow CFU-E were decreased by 97% and splenic CFU-E by 99%. Tibial BFU-E were not decreased by Acto, although there was a 66% diminution in splenic BFU-E. Acto increased tibial CFU-S, but splenic CFU-S and tibial and splenic CFU-C were unchanged. Thus Acto inhibits erythropoiesis by suppressing the ability of immediate committed erythroid precursors of CFU-E or CFU-E themselves to differentiate further in response to Ep. Acto does not affect survival or proliferation of the less differentiated cells--CFU-C, CFU-S, and marrow BFU-E. The suppression of splenic BFU-E in Acto-treated mice may indicate that marrow and splenic BFU-E are basically different stem cells. Alternatively, Acto treatment may impair migration of BFU-E from marrow to spleen.

Animals↗
PubMed1978

[Technology and real performances of a new circuit for new pacemaker (author's transl)].

Continuing evolution in cardiac stimulation today imposes on PM manufacturers the need to submit their products under new criteria, such as: contained dimensions, functional complexity and longer periods of patient care. PM electronic circuity plays a determinant role in meeting the best solution of these problems. Thick film hybrid technology has been chosen by the Authors because it is deemed to be the best compromise for the present goals, such as: low power consumption, low weight and small size, electrical parameters stability, functional complexity and high circuitry density, Hi-Rel performance for longer working life. A little space has been reserved for schematic diagrams of the manufacturing cycle and the applied technology; particular evidence has been shown concerning selection criteria for circuitry component selection and Hi-Rel tests for the end product. Hi-Rel and qualification standards have been selected by the Authors from MIL-STD 883 methods and AAMI-FDA pacemakers standards. Practical results of the application of this methodology can be summarised as follows: only 44-50% of the total circuits pass the complete cycle of tests and thus are used for PM manufacture; electronic failure rate in the implanted units is 0.024% failure per month.

Electronics↗
PubMed1977

Persistence of poliovirus 1 in soil and on vegetables grown in soil previously flooded with inoculated sewage sludge or effluent.

Land disposal of sewage sludge and effluent is becoming a common practice in the United States. The fertilizer content and humus value of such wastes are useful for agricultural purposes, and the recycling of sewage onto the land eliminates many of our stream pollution problems. The potential exists for crops grown in such irrigated soil to be contaminated by viruses that may be present in the sewage. Studies were initiated to determine viral persistence in soil and on crops grown under natural conditions in field plots that had been flooded to a depth of 1 inch (2.54 cm) with poliovirus 1-inoculated sewage wastes. Lettuce and radishes were planted in sludge- or effluent-flooded soil. In one study, the vegetables were planted 1 day before flooding, and in another they were planted 3 days after the plots were flooded. Survival of poliovirus 1 in soil irrigated with inoculated sewage sludge and effluent was determined during two summer growing seasons and one winter period. The longest period of survival was during the winter, when virus was detected after 96 days. During the summer, the longest survival period was 11 days. Poliovirus 1 was recovered from the mature vegetables 23 days after flooding of the plots had ceased. Lettuce and radishes are usually harvested 3 to 4 weeks after planting.

Poliovirus↗
PubMed1975

Collaborative study of the glass wool filtration method for the recovery of virus inoculated into ground beef.

A method for estimating viral population levels in ground beef was studied collaboratively in 7 laboratories. The collaborators recovered virus from 6 inoculated samples. Three samples were replicates of the high virus concentration 050 plaque-forming units (pfu)/g) and 3 replicates represented the low concentration (10 pfu/g). Six of the 7 collaborators recovered acceptable levels of virus from the samples. The per cent of variation was 30.6 for the high concentration and 18.5 for the low concentration. Collaborators did not differ from one another significantly in the results obtained for the 10 pfu/g samples, but results from one collaborator were significantly low for the recovery of virus from the 50 pfu/g samples. The results indicate that the glass wool filtration method is adequate for the detection of a number of viruses that may be found in foods. The method has been adopted as official first action.

Animals↗
PubMed1973

Gamma radiation inactivation of coxsackievirus B-2.

The radioresistance of coxsackievirus B-2 was studied when the virus was suspended in Eagle minimal essential medium, distilled water, cooked ground beef, and raw ground beef and irradiated at various temperatures in a cobalt-60 gamma radiation source. The number of surviving viruses at given doses of radiation was determined by a plaque assay system. All destruction curves indicated a first-order reaction. When the virus was irradiated in minimal essential medium at temperatures of -30, -60, and -90 C, D values (in Mrad) were 0.69, 0.59, and 0.64, respectively. When the virus was suspended in water and irradiated at -90 C, the D value was 0.53. Cooked ground beef containing the virus was irradiated at temperatures ranging from 16 to -90 C. The D values were 0.70 (16 C), 0.76 (0.5 C), 0.68 (-30 C), 0.78 (-60 C), and 0.81 (-90 C). Raw ground beef containing the virus was irradiated at -30, -60, and -90 C, and the D values were respectively 0.75, 0.71, and 0.68. The D values indicate that the rate of viral inactivation was dependent on the suspending menstrum.

Analysis of Variance↗
PubMed1973

Comparison of methods for the recovery of virus inoculated into ground beef.

Various methods for the recovery of virus inoculated into ground beef were investigated in an attempt to develop a sensitive system that could be used to detect viral contaminants in market foods. A 100-g sample, inoculated with poliovirus 1, was suspended in 150 to 900 ml of Eagle minimum essential medium, pH 8.5, and mixed in either plastic bags or plastic cups on a mechanical shaker. The particulate materials were removed by means of cheese cloth, glass wool, woven fiber glass, or low-speed centrifugation. Large volumes of fluid were concentrated by ultrafiltration. Microbiological contamination was controlled by high antibiotic concentrations or by filtration. Quantitative plaque-forming-unit recovery of the virus was determined by utilizing an agar overlay technique on Vero cell cultures. The data indicated that from 20 to 50% of the seeded virus could be recovered from a 100-g sample of ground beef. The glass wool and woven fiber glass methods were the most effective, with recovery of approximately 50% of the inoculated virus.

Acetates↗