Biomedical subjects

G Schoeters

Publications and source records attributed to G Schoeters.

At least 19 recordsLinked to original sources

PubMed2006

Determinants of variability of protein content, volume and pH of exhaled breath condensate.

Collection of exhaled breath condensate (EBC) is a simple and noninvasive method to obtain information on the respiratory system. Different mediators can be determined in EBC. However, determinants of variability are not well described. The aim of this study was to evaluate variability of pH, volume and protein concentration of EBC between individuals and between sampling times. Therefore, EBC was collected from 20 healthy volunteers on two different days. Median pH for all samples, measured 5 min after collection without deaeration, was 6.17. Median volume was 1.70 ml and median total protein concentration was 1.02 microg/ml. Coefficients of variation were 5.17%, 21.84% and 37.93%, respectively. No intra- or interday variability could be found, except for the first collection time. Between individuals, significant differences were observed for all three mediators. Age, height and gender can explain part of this variation. In conclusion, no significant difference between sampling times on the same day or on different days was obtained for pH, volume and total protein concentration, provided that subjects are experienced in collecting EBC.

Adolescent↗

PubMed2006

Endocrine disrupters and human puberty.

In this overview of the literature, epidemiological research studying the effect of endocrine disrupters on the onset of puberty is summarized. In girls, earlier age at menarche was reported after exposure to polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), persistent pesticides [dichlorodiphenyltrichloroethane (DDT)] and phthalate esters. However, several other studies found no effect of these compounds on age at menarche or pubertal Tanner stages. One study reported a delaying effect of dioxin-like compounds on breast development. In boys, exposure to PCBs, PCDFs or the pesticide endosulfan was associated with delayed puberty or decreased penile length. Much of the results found in population studies are in accordance with experimental studies in animals. However, the mixture of different components with antagonistic effects (oestrogenic, anti-oestrogenic, anti-androgenic) and the limited knowledge about the most critical window for exposure (prenatal, peri-natal and pubertal) may hamper the interpretation of results.

Androgen Antagonists↗

PubMed2005

Flow cytometric characterisation of antigen presenting dendritic cells after in vitro exposure to diesel exhaust particles.

The aim of this study was to obtain more insight into the effect of diesel exhaust particles (DEP) on the maturation of primary human dendritic cells. Monocyte-derived dendritic cells (Mo-DC) derived from seven different donors were exposed to different DEP concentrations (0.2,2,20,200 and 2,000 ng/ml) in the presence or absence of lipopolysaccharide (LPS), and changes in the surface expression of HLA-DR, CD86 and CD83 were examined. Exposure of Mo-DC to DEP alone did not alter expression levels of any of the markers. Treatment with LPS alone increased the expression levels of all three surface markers, although the levels were not significantly different compared to untreated DCs. The LPS-induced marker expression could be further enhanced by co-stimulation of the cells with DEP. Statistical significantly increased levels of CD83 expression were observed after exposure to 0.2 (p=0.018), 20 (p=0.010) and 200 ng/ml (p=0.047) DEP combined with LPS in the group of responders. We conclude that DEP has an adjuvant effect on LPS-induced maturation of Mo-DC.

Antigens, CD↗

PubMed2003

Application of the CFU-GM assay to predict acute drug-induced neutropenia: an international blind trial to validate a prediction model for the maximum tolerated dose (MTD) of myelosuppressive xenobiotics.

In a previous study of prevalidation, a standard operating procedure (SOP) for two independent in vitro tests (human and mouse) had been developed, to evaluate the potential hematotoxicity of xenobiotics from their direct and the adverse effects on granulocyte-macrophages (CFU-GM). A predictive model to calculate the human maximum tolerated dose (MTD) was set up, by adjusting a mouse-derived MTD for the differential interspecies sensitivity. In this paper, we describe an international blind trial designed to apply this model to the clinical neutropenia, by testing 20 drugs, including 14 antineoplastics (Cytosar-U, 5-Fluorouracil, Myleran, Thioguanine, Fludarabine, Bleomycin, Methotrexate, Gemcitabine, Carmustine, Etoposide, Teniposide, Cytoxan, Taxol, Adriamycin); two antivirals (Retrovir, Zovirax,); three drugs for other therapeutic indications (Cyclosporin, Thorazine, Indocin); and one pesticide (Lindane). The results confirmed that the SOP developed generates reproducible IC90 values with both human and murine GM-CFU. For 10 drugs (Adriamycin, Bleomycin, Etoposide, Fludarabine, 5-Fluorouracil, Myleran, Taxol, Teniposide, Thioguanine, and Thorazine), IC90 values were found within the range of the actual drug doses tested (defined as the actual IC90). For the other 10 drugs (Carmustine, Cyclosporin, Cytosar-U, Cytoxan, Gemcitabine, Indocin, Lindane, Methotrexate, Retrovir, and Zovirax) extrapolation on the regression curve out of the range of the actual doses tested was required to derive IC90 values (extrapolated IC90). The model correctly predicted the human MTD for 10 drugs out of 10 that had "actual IC90 values" and 7 drugs out of 10 for those having only an extrapolated IC90. Two of the incorrect predictions (Gemcitabine and Zovirax) were within 6-fold of the correct MTD, instead of the 4-fold range required by the model, whereas the prediction with Cytosar-U was approximately 10-fold in error. A possible explanation for the failure in the prediction of these three drugs, which are pyrimidine analogs, is discussed. We concluded that our model correctly predicted the human MTD for 20 drugs out of 23, since the other three drugs (Topotecan, PZA, and Flavopiridol) were tested in the prevalidation study. The high percentage of predicitivity (87%), as well as the reproducibility of the SOP testing, confirm that the model can be considered scientifically validated in this study, suggesting promising applications to other areas of research in developing validated hematotoxicological in vitro methods.

Acute Disease↗

PubMed2003

Effect of coexposure to 50 Hz magnetic fields and an aneugen on human lymphocytes, determined by the cytokinesis block micronucleus assay.

Interference of 50 Hz extremely low frequency magnetic fields (ELF-MF) with the known aneugen vinblastine (VBL) on micronucleus formation was tested with the in vitro cytokinesis block micronucleus assay in human lymphocyte cultures. Isolated lymphocyte cultures were prepared from 18 individuals. Three groups of quadruplicate cultures from six unrelated individuals were exposed to 50 Hz ELF-MF of background (bkg), 80 and 800 microT, respectively, during the complete incubation period (72 h). Twenty-four hours after culture initiation, one replicate culture from each individual within each ELF-MF group was exposed to 0, 5, 10, or 15 ng/ml VBL. The isolated lymphocyte cultures were scored for the presence of micronuclei, the nuclear division index (NDI), and apoptosis. As expected, increased VBL concentration resulted in an increased micronucleus and apoptosis frequency and in a decreased NDI. In the presence of VBL, there was a systematic tendency for increased micronucleus and apoptosis frequency in the ELF-MF exposed groups compared to the bkg group. In the absence of VBL, we observed no statistically significant effect of ELF-MF on micronucleus induction or apoptosis frequency, but the NDI was significantly higher in the 800 microT group compared to the other groups, suggesting an effect of ELF-MF on cell proliferation. An interaction between ELF-MF and VBL on NDI was observed. This interaction reflected the drastic decrease in NDI due to coexposure to VBL.

Adult↗

PubMed2002

Persistent organochlorine pollutants in human serum of 50-65 years old women in the Flanders Environmental and Health Study (FLEHS). Part 1: Concentrations and regional differences.

In 1999, a campaign of the Flemish Ministry of Health, Belgium was set up to assess pollutant concentrations and related health effect biomarkers in humans living in two regions of Flanders. The study was called the 'Flemish Environment and Health Study' (FLEHS). One of the goals was to measure present concentrations of persistent organochlorine pollutants in a Flemish population and to compare values obtained from pooled and individual serum samples. Concentrations of selected organochlorine pesticides, polychlorinated biphenyls (PCB) and polychlorinated dibenzo-p-dioxins (PCDD) and furans (PCDF) were measured by gas chromatography-mass spectrometry. TEQ values were also assessed by Chemical-Activated LUciferase gene eXpression (CALUX) bioassay. The study population consisted of 200 women between 50 and 65 years living in two areas of Flanders, Belgium. Because of the large volumes serum needed for all measurements, the concentrations of organochlorines were measured in 47 pooled serum samples originating from these women. The concentrations of the indicator PCBs (359.8 ng/g fat) and organochlorine pesticides (hexachlorobenzene, p,p'-dichlorodiphenyldichloroethylene, p,p'-dichlorodiphenyl-trichloroethane, lindane and pentachlorophenol), were comparable to those found in other European countries. The concentrations of PCDD/PCDFs showed another picture. With a median value of 48 pg WHO-TEQ/g fat, the women had 2-fold higher levels than a comparable age group from Germany examined in 1996. The mean total WHO-TEQ including PCDD/F, non-ortho and mono-ortho PCBs was 72.7 pg WHO-TEQ/g fat, whereas the CALUX-TEQ mean value was only 35.0 pg TEQ/g fat. In order to assess the pooling procedure, indicator PCBs and CALUX-TEQs were measured in all 200 individuals that were integrated in the pools. The measured values were comparable to the pool results: 390.0 ng/g fat and 41.6 pg TEQ/g fat respectively. It was concluded that pooling of serum samples offers the possibility to measure exposure in the whole study population on a more cost-effective way. However, because of statistical power loss and no possibility of confounder adjustment, pooling is not the most effective way to study regional differences.

Aged↗

PubMed2002

Increased HLA-DR expression after exposure of human monocytic cells to air particulates.

BACKGROUND: The expression of HLA-DR on the cell membrane of antigen-presenting cells is of major importance for the induction of an allergic response in the airways. Environmental particulates are thought to play an important role in inducing or enhancing allergic sensitization, possibly by increasing the expression of HLA-DR on the cell membrane of antigen-presenting cells. In addition, these particulates may synergize with common sensitizing agents in inducing or enhancing HLA-DR and thus antigen presentation. OBJECTIVE: In this study, we investigated the potential of three particle types, namely carbon black, diesel exhaust particles and urban air particulates (0.1-1000 ng/cm(2)), to induce the expression of HLA-DR on differentiated THP-1 cells, taken as a model for alveolar macrophages. We also assessed the "adjuvant" potential of the particles on interferon (IFN)-gamma, a known enhancer of HLA-DR. RESULTS: By themselves, the particles (0.1-1000 ng/cm(2)) were not able to induce HLA-DR on the THP-1 cells after an incubation of 48 h. However, even at very low concentrations, carbon black (from 1 ng/cm(2) on) and diesel exhaust particles (from 0.1 ng/cm(2) on), interacted with IFN-gamma (100 U/mL) to enhance HLA-DR expression (up to 2.5-fold increase). CONCLUSION: This finding may reflect in vitro one of the mechanisms by which pollutant particles exert an "adjuvant" activity and may partially explain how exposure to particles can be related to the enhancement of allergic sensitization.

Air Pollution↗

PubMed2001

Comparison of CALUX-TEQ values with PCB and PCDD/F measurements in human serum of the Flanders Environmental and Health Study (FLEHS).

Adult↗

PubMed2001

Renal function, cytogenetic measurements, and sexual development in adolescents in relation to environmental pollutants: a feasibility study of biomarkers.

BACKGROUND: Human exposure to chemicals is normally monitored by measurement of environmental pollutants in external media. We investigated whether biomarkers in adolescents can show exposure to, and health effects of, common environmental pollutants. METHODS: We recruited 200 17-year-old adolescents (120 girls) from a rural control area and from two suburbs polluted by a lead smelter and two waste incinerators. We measured biomarkers of exposure and of effect in blood and urine samples, and obtained questionnaire data. School doctors measured testicular volume and staged sexual maturation. FINDINGS: Internal exposure was mostly within current standards. Concentrations of lead and cadmium in blood, PCBs (polychlorinated biphenyls) and dioxin-like compounds in serum samples, and metabolites of VOCs (volatile organic compounds) in urine were higher in one or both suburbs than in the control area. Children who lived near the waste incinerators matured sexually at an older age than others, and testicular volume was smaller in boys from the suburbs than in controls. Biomarkers of glomerular or tubular renal dysfunction in individuals were positively correlated with blood lead. Biomarkers of DNA damage were positively correlated with urinary metabolites of PAHs (polycyclic aromatic hydrocarbons) and VOCs. Interpretation Biomarkers can be used to detect environmental exposure to pollutants and measure their biological effects before overt disease develops. Our findings suggest that current environmental standards are insufficient to avoid measurable biological effects.

Adolescent↗

PubMed2001

Genotoxic effects of carbon black particles, diesel exhaust particles, and urban air particulates and their extracts on a human alveolar epithelial cell line (A549) and a human monocytic cell line (THP-1).

The possible genotoxicity of small particulate matter has been under investigation for the last 10 years. Diesel exhaust particles (DEP) are considered as "probably carcinogenic" (IARC group 2A) and a number of studies show genotoxic effects of urban particulate matter (UPM). Carbon black (CB) is carcinogenic in rats. In this study the cytotoxic and genotoxic potency of these three particle types was investigated by exposing human cells (A549 and THP-1 cell lines) in vitro to CB, DEP (SRM 1650, NIST), and UPM (SRM 1648, NIST) for 48 hr. Cytotoxicity was assessed using the Alamar Blue assay, whereas genotoxicity was assessed using the single-cell gel electrophoresis (comet assay). The particles were characterized with regard to their mean diameter in tissue culture medium (CB 100 nm, DEP 400 nm, UPM 2 microm), their total carbon content (CB 99%, DEP 85%, UPM 15%), and their acid-soluble metal composition (UPM >> CB approximately DEP). The concentrations ranged from 16 ng/ml to 16 microg/ml for cytotoxicity tests and from 16 ng/ml to 1.6 microg/ml for genotoxicity tests. In both assays, paraquat was used as a reference chemical. The CB, DEP, and UPM particles showed no significant cytotoxicity. However, all three particles were able to cause significant DNA damage, although to a different extent in the two cell lines. The genotoxicity of washed particles and dichloromethane extracts was also investigated. In THP-1 cells CB washed particles and DEP extracts caused significant DNA damage. This difference in effect may be related to differences in size, structure, and composition of the particles. These results suggest that CB, DEP, and UPM are able to cause DNA damage and, therefore, may contribute to the causation of lung cancer. More detailed studies on influence of size, structure, and composition of the particles are needed.

Air Pollutants↗

PubMed2001

Observations as to male fertility in the Flemish environment and health studies.

We report the observations made on 101 healthy non-smoking men aged 21-40 (50 from two industrial suburbs of the big city of Antwerp and 51 from Peer, a predominantly rural municipality with 14,622 inhabitants, 70 km east of Antwerp, chosen as the "control" area in spite of its intensive agriculture). Persons with known occupational exposures, persons working in a region with characteristics clearly different from the area of residence, and people commuting over long distances were excluded from the study. Sperm morphology was significantly worse in Peer than in Antwerp. Serum testosterone levels were significantly lower in Peer than in Antwerp. The proportions of men with very low and low serum testosterone levels, of men with very low and low spermatozoa concentrations and of men with very low and low percentages of spermatozoa with normal morphology, were all higher in Peer than in Antwerp. We speculate that both the lower testosterone concentrations and the poorer sperm quality are due to disturbance of the hypothalamic-pituitary-testicular function by hormone disrupters. Our data suggest that exposure to levels of environmental pollution which are widespread in developed nations, can have unfavourable effects on endocrine equilibrium and may disturb male fertiline disrupters.

Adult↗

PubMed2000

Protective effect of the bile salt hydrolase-active Lactobacillus reuteri against bile salt cytotoxicity.

Bacterial bile salt hydrolysis is considered a risk factor for the development of colon cancer because of the risk of forming harmful secondary bile salts after an initial deconjugation step. In this study, the influence of enhanced bacterial bile salt transformation by the bile salt hydrolase-active Lactobacillus reuteri was studied in batch culture using the microbial suspension of the Simulator of the Human Intestinal Microbial Ecosystem; (SHIME), which was supplemented with oxgall at 5 g/l or 30 g/l. Changes in the fermentative capacity of the microbial ecosystem and the (geno)toxic properties of the SHIME supernatants were investigated. Increasing concentrations of oxgall inhibited the fermentation. Transient cell toxicity was observed for samples supplemented with 5 g oxgall/l, while samples with 30 g oxgall/l exhibited toxicity. The results of the haemolysis test suggest that the detrimental effects were probably due to the membrane-damaging effects of bile salts. In all cases, the adverse effects could be counteracted by the addition of 7.5 +/- 0.5 log10 CFU L. reuteri/ml. Plausible mechanisms for the protective properties of L. reuteri could involve a precipitation of the deconjugated bile salts and a physical binding of bile salts by the bacterium, thereby making the harmful bile salts less bioavailable.

Amidohydrolases↗

PubMed1998

Comparative sensitivity of 20 bioassays for soil quality.

Increasing evidence suggests that the use of a single bioassay will never provide a full picture of the quality of the environment. Only a test battery, composed of bioassays of different animal and plant species from different trophic levels will reduce uncertainty, allowing an accurate assessment of the quality of the environment. In the present study, a test battery composed of 20 bioassays of varying biological endpoints has been compared. Apart from lethality and reproductive failure in earthworms, springtails, nematoda, algae and vascular plants, these endpoints also included bioavailibility of metals (bacteria), heat-shock induction (nematodes, algae), DNA damage (bacteria, earthworm, vascular plants), beta-galactosidase (Daphnia) and esterase activity (algae) and a range of immunological parameters (earthworm). Four chemicals (cadmium, phenol, pentachlorophenol and trifluralin)--each representing a different toxic mode of action--were applied in a dilution series (from 1 mg/kg up to 1000 mg/kg) onto OECD standard soil. The tests have been performed both on these artificially contaminated soil samples and on aqueous extracts subsequently obtained from these soils. The results show that the immunological parameters and the loss of weight in the earthworms were among the most sensitive solid-phase assays. Esterase inhibition and heat-shock induction in algae were shown to be extremely sensitive when applied to soil extracts. As previously shown at the species level, no single biological endpoint was shown to be the most sensitive for all four modes of toxic action.

Animals↗

PubMed1993

Characterization of a 5-fluorouracil-enriched osteoprogenitor population of the murine bone marrow.

In the presence of beta-glycerophosphate and vitamin C, cultures of normal mouse bone marrow cells form three-dimensional structures that stain positive with the Von Kossa technique and express alkaline phosphatase (ALP), collagen type I, and osteocalcin. Little is known about the characteristics and frequency of the cells that contribute to this phenomenon. Most likely, mature osteoblastic cells do not contribute to the nodule formation because no osteocalcin expressing cells are detected in the flushed marrow by in situ hybridization. Limiting dilution analysis shows that, in normal bone marrow, 1 of 2.2 x 10(5) cells has the potency to form a bone nodule and to express ALP, collagen, and osteocalcin in a temporal fashion. Upon in vivo treatment with 5-fluorouracil (5-FU), this frequency increases 12-fold, eg, 1 in 1.75 x 10(4) cells shows osteogenic activity. In comparison, fibroblast colony forming cells occur at a frequency of 1 of 2.5 x 10(4) or 1 of 5 x 10(3) plated cells in normal or 5-FU-treated marrow, respectively. Using density centrifugation, the majority of the osteoprogenitor cells in 5-FU marrow are found in the low-density (1.066 to 1.067 g/mL) fractions. In addition, these cells bind to nylon wool but not to plastic and aggregate in the presence of wheat germ agglutinin and soybean agglutinin. Scanning and transmission electron microscopy shows that the bone nodules in 5-FU marrow cultures are composed of fibroblastoid cells embedded in a mineralized collagen matrix. In conclusion, our results show that a quiescent cell population in the murine bone marrow with fibroblastoid characteristics contributes to the formation of bone-like nodules in vitro.

Alkaline Phosphatase↗

PubMed1992

Establishment of an osteogenic cell line derived from adult mouse bone marrow stroma by use of a recombinant retrovirus.

In order to characterize fibroblastic colony-forming units (CFU-F) from murine bone marrow in relation to osteogenesis, adherent cells of 7-day-old BALB/c mouse bone marrow cultures were infected with a recombinant retrovirus (N2/ delta fosB) containing the bacterial neomycin resistance gene. One of the G418-resistant clones, MN7, was selected for further analysis on the basis of its high expression of the bone-specific alkaline phosphatase. The cells have now been in culture for more than 1 year and maintain a stable phenotype. The osteogenic nature of the immortalized clone MN7 was demonstrated as follows: (1) Mineralization was detected by 85Sr uptake and with the Von Kossa staining method only after in vitro cultivation on a collagen type I matrix. (2) Osteoblastic phenotype markers, including the synthesis of type I collagen, osteonectin, and the bone-specific isoenzyme of alkaline phosphatase were expressed in vitro. (3) MN7 cells responded to bone effectors such as parathyroid hormone and 1,25-dihydroxyvitamin D3. (4) Intraperitoneal injection of MN7 cells into 1-day-old BALB/c mice produced typical osteosarcomas in all animals. We conclude that MN7, derived entirely in vitro from a stromal CFU-F colony, represents a stable murine osteosarcoma cell line expressing the osteoblastic phenotype and provides the first direct evidence needed to establish adult mouse marrow-derived, nonhematopoietic stromal cells as osteoprogenitors.

Alkaline Phosphatase↗

PubMed1992

Haemopoietic long-term bone marrow cultures from adult mice show osteogenic capacity in vitro on 3-dimensional collagen sponges.

Adult murine bone marrow cells, cultured under conditions for long-term haemopoietic marrow cultures, produce bone matrix proteins and mineralized tissue in vitro, but only after the adherent stromal cells were loaded on a 3-dimensional collagen sponge. Provided more than 8 x 10(6) cells are loaded, mineralization as measured by 85Sr uptake from the culture medium, occurred in this 3-dimensional configuration (3-D) within 6 days. In contrast if undisrupted marrow fragments (containing more than 10(7) cells) are placed directly on a collagen sponge, then it requires more than 10 days before significant mineralization can similarly be detected. The 2-dimensional (2-D) long-term marrow culture system allows prior expansion of the stromal cells and some differentiation in an osteogenic direction within the adherent stromal layer. This is suggested by the presence of type I collagen and alkaline phosphatase positive cells. However; synthesis of osteonectin and a bone specific protein, osteocalcin, as well as calcification are only observed in 3-D cultures. Electron microscopy demonstrated hydroxyapatite mineral on collagen fibres, osteoblast-like cells, fibroblasts, cells which accumulated lipids, and macrophages which were retained on the collagen matrices. Irradiation of confluent long-term bone marrow cultures, prior to their loading on the collagen sponge showed that haemopoietic stem cells are not necessary for the mineralization.

Animals↗

PubMed1991

Culture of hematopoietic stem cells purified from murine bone marrow.

The results of the Y-chromosome in situ hybridization experiments, the MRA assessment, and the long-term production of CFU-GM in vitro indicate that our protocol to sort low density WGA+, 15/1.1-, Rh123 dull cells enriches about 200-fold for PHSC. Assays for spleen colony formation (CFU-S) and radioprotection (30-day survival) were shown to be unspecific for PHSC, and, therefore, we lack a quantitative PHSC assay. The absolute number of PHSC in the bone marrow is not known any more, the purity of our sorted population likewise is unknown. Long-term repopulating cells (PHSC) could be separated from short-term repopulating ones by using Rh123 staining. The short-term repopulating cells (Rh123 bright) provided sufficient offspring to protect lethally irradiated mice until endogenous PHSC could reconstitute hematopoiesis. These cells are therefore of interest for bone marrow transplantation, because they provide radioprotection without long-term repopulation and graft-versus-host disease. For gene therapy these cells are of limited use, and PHSC with extensive replication are needed. The PHSC were not cultured successfully. Less than 15% of the sorted Rh123 dull cells responded in semisolid or liquid cultures in the presence of growth factors. Proliferation without differentiation was not observed. This may indicate that the right growth factor has not been found yet. On the other hand, about 30% of the cells responded in stromal layers of long-term bone marrow cultures and prolonged CFU-GM production and cobblestone area formation were observed there, suggesting that cell-cell contact and adherence molecules play a regulatory role in PHSC replication.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Stromal cells from murine developing hemopoietic organs: comparison of colony-forming unit of fibroblasts and long-term cultures.

The adherent stromal layer in long-term marrow cultures is essential to the proliferation and differentiation of hemopoietic cells. Adhering cells are heterogeneous and morphologically not adequately characterized. Comparative morphological studies were conducted on adherent cells in short-term clonal assays and long-term cultures derived from liver and bone marrow. Liver and bone marrow at different developmental ages have different hemopoietic activities in vivo and in vitro, as tested via CFU-GM recovery in long-term cultures. Adherent cells from each organ were recovered at an age with high hemopoietic activity (fetal liver and adult bone marrow) and at an age with low hemopoietic activity (neonatal liver and bone marrow). The presence of macrophages, alkaline phosphatase, acid phosphatase, myeloperoxidase, sulfated and non-sulfated glycosaminoglycans (GAGs) and fibronectin was compared. For a given organ, CFU-f colonies showed characteristics similar to those of the confluent adherent stromal layer in long-term cultures. The presence of macrophages and GAGs (sulfated and non-sulfated) in the adherent layer were directly related to the hemopoietic activity. The amount of alkaline phosphatase-positive cells and the amount of fibronectin showed no correlation with the hemopoietic activity of the cultures.

Alkaline Phosphatase↗