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Biomedical subjects

M Gregoire

Publications and source records attributed to M Gregoire.

At least 19 recordsLinked to original sources
PubMed2006

Culture medium and protein supplementation in the generation and maturation of dendritic cells.

Dendritic cells (DC) are powerful antigen-presenting cells that have drawn many attentions due to the recent development of anti-cancer vaccines. Clinical grade production of monocyte-derived DC (Mo-DC) is extensively studied, and many efforts are made to develop and improve clinical standard operating procedures. Most of the parameters involved, such as the cytokines and maturation agents, have been widely assessed. However, very few are investigated about how culture medium and additional protein components affect DC yield, viability and maturation. Thus, our study aimed to compare the impact of standard culture medium on Mo-DC differentiation and maturation. Commercially available media for hematopoietic cell culture as well as different protein supplementations, that is foetal calf serum (FCS), autologous plasma (AP), human serum (HS) and human serum albumin (HSA) were tested. Culture yields, cell viability and DC maturation were investigated. Differentiation yields were similar between the conditions used. However, we evidenced significant differences in terms of cytotoxicity and DC maturation (phenotypic and functional). This underscores the importance of defining culture medium composition in clinical standard operating procedures to insure quality control, and also when preparing DC for experimental uses.

Cell Culture Techniques↗
PubMed2001

Standardized generation of fully mature p70 IL-12 secreting monocyte-derived dendritic cells for clinical use.

Dendritic cells (DC) have been shown to be efficient antigen-presenting cells (APC) and, as such, could be considered ideal candidates for cancer immunotherapy. Immature DC (iDC) efficiently capture surrounding antigens; however, only mature DC (mDC) prime naive T lymphocytes. Clinical trials using DC-based tumor vaccines have achieved encouraging, but limited, success, possibly due to the use of immature or incompletely mature DC. Thus, it was apparent that a method capable of generating large numbers of fully functional iDC, their pulsing with desired form of tumor antigens and the subsequent complete and reproducible maturation of iDC is needed. Therefore, we compared two different methods of producing large numbers of iDC. Both protocols yielded comparable numbers of cells with an iDC phenotype with phagocytic function. We next determined which of the clinically applicable activators could induce the complete and reproducible maturation of DC, in order to define the most suitable combination for future clinical trials. Only a combination of TNFalpha + Poly (I:C), or a previously described cytokine cocktail of TNFalpha + IL-1beta + IL-6 + prostaglandin E2, induced the complete activation of the whole DC population, as assessed by the cell surface expression of CD83 and costimulatory molecules. The matured DC were functionally superior to iDC in their ability to stimulate the proliferation of allogeneic lymphocytes and autologous keyhole limpet hemocyanin (KLH)-specific T lymphocytes. Furthermore, only the combination of TNFalpha + Poly (L:C) activated DC to produce large amounts of biologically active p70 IL-12. Thus DC maturation by TNFalpha + Poly (I:C) could efficiently bias T cell response towards Th1 response. Implementation of our results into clinical protocols used for DC generation could be beneficial for future immunotherapy trials.

Apoptosis↗
PubMed2001

Characterization of alpha-smooth muscle actin positive cells in mineralized human dental pulp cultures.

In response to injury, pulp precursor cells can differentiate into odontoblast-like cells that produce reparative dentine. In culture, pulp cells form mineralizing nodules, but the characteristics of the cells involved in this process are still not fully known. Human pulp cells for culture were obtained from coronal pulp isolated from non-erupted molars, and were maintained in RPMI 1640 medium supplemented with fetal calf serum. Nodules were forming in all human pulp primary cultures (HPPc) and human pulp subcultures observed until their fifth passage (HPSc<5). Mineralization of the nodules was confirmed by the presence of calcium and phosphate that were quantified by X-ray microanalysis. Specific immunolabeling revealed alpha-smooth muscle actin and vimentin in both HPPc and HPSc<5 cells. Cells positive for alpha-smooth muscle actin were either isolated or gathered together in the nodules. Under transmission electron microscopy, some cells in primary pulp cultures exhibited features typical of myofibroblasts or pericytes, such as stress fibers, fibronexus, indented nuclei and gap-junctions. These cells were frequently in close contact with mineral deposits. This work demonstrates for the first time the presence of pericytes or myofibroblasts in mineralized human pulp cultures, but further investigation is required to determine their origin, role and degree of differentiation.

Actins↗
PubMed2000

Pentosan polysulfate therapy for chronic nonbacterial prostatitis (chronic pelvic pain syndrome category IIIA): a prospective multicenter clinical trial.

OBJECTIVES: Chronic nonbacterial prostatitis/chronic pelvic pain syndrome (CPPS) has clinical and perhaps etiologic characteristics similar to interstitial cystitis. Pentosan polysulfate sodium (PPS), an oral medication indicated for the treatment of interstitial cystitis, has shown moderate benefit in reducing chronic pelvic pain and voiding symptoms in patients with interstitial cystitis. We undertook a prospective open-label, multicenter Phase II pilot study to examine the potential efficacy of PPS in the treatment of CPPS in men, using outcome tools validated for CPPS in men. METHODS: Patients with a diagnosis consistent with National Institutes of Health (NIH) CPPS category IIIA (inflammatory) were treated with PPS, 100 mg three times daily, for 6 months. The evaluation at baseline, 3 months, and 6 months consisted of the Symptom Severity Index, a Symptom Frequency Questionnaire, the NIH-Chronic Prostatitis Symptom Pain Index (NIH-CPSI), a quality-of-life assessment, and a subjective global assessment. RESULTS: Thirty-two patients (mean age 45.5 +/- 11 years; duration of symptoms 9.2 +/- 12 years) were enrolled in five centers; 28 patients were available for evaluation. Seven patients experienced drug-related side effects, including hair loss (n = 2), headache (n = 2), mild nausea (n = 1), mild weight gain (n = 1), and skin flushing (n = 1). The decrease in frequency (Symptom Frequency Questionnaire 28.1 to 17.9), severity (Symptom Severity Index 53.6 to 36.3), and combined location/frequency/severity of pain (NIH-CPSI pain 14.5 to 9.2) symptom scores at 6 months compared with baseline was significant. The decrease was associated with a significant improvement in patients' quality of life (quality-of-life assessment 5.3 to 3.8). Forty-three percent of the patients had a greater than 50% improvement in the Symptom Frequency Questionnaire, Symptom Severity Index, and NIH-CPSI (rated as clinically significant improvement). At 6 months, mild, moderate, and marked improvement was noted (subjective global assessment) by 33%, 19%, and 15% of the patients, respectively. CONCLUSIONS: PPS is well tolerated and appears to have efficacy in reducing the severity and frequency of general symptoms, reducing specific pain symptoms, and improving the quality of life in many male patients with CPPS. The results of this study justify the initiation of a randomized controlled trial comparing the safety and efficacy of PPS to placebo.

Adult↗
PubMed1997

Effects of hydroxyapatite particles on periodontal ligament fibroblast-like cell behavior.

Although hydroxyapatite (HA), a synthetic calcium phosphate, is used in restoring bone defects associated with periodontal diseases, its specific effect on the periodontal ligament fibroblast population during the regeneration process is unclear. To determine the cellular events occurring in the presence of HA, human periodontal ligament fibroblasts (HPLF) were isolated and maintained in culture. The specificity of the cells was evidenced by their morphology, deposition of extracellular matrix components, and alkaline phosphatase (ALP) activity (as a marker of osteoblastic differentiation of HPLF). Phase-contrast investigations revealed morphological alterations of cells in contact with HA particles. Transmission electron microscopy demonstrated the phagocytotic process of HPLF toward HA particles. Moreover, the presence of HA particles was significantly related to an increase in the protein synthesis activity and a decrease in the proliferation and ALP-specific activity of HPLF. These results provide new information on the phenotypic expression of HPLF, which is comparable to that of osteoblastic cells. A subpopulation of HPLF may be influenced by the presence of HA to undergo transient dedifferentiation prior to redifferentiating into osteoblasts. This process may be important as a means by which HA acts as an osteoconductive material. This experimental study improves our understanding of the cellular processes which occur during healing and regeneration of periodontal defects after implantation of biomaterials.

Alkaline Phosphatase↗
PubMed1996

Antihypertensive therapy in older patients with isolated systolic hypertension: the Syst-Eur experience in general practice

Background and objective. This interim report from the Syst-Eur trial investigated the level of blood pressure control achieved during the double-blind period in patients followed in general practices. Methods. In the Syst-Eur trial elderly patients (60 years or older) with isolated systolic hypertension were randomized to either active or placebo treatment. Active treatment consisted of nitrendipine combined with enalapril and/or hydrochlorothiazide to reduce systolic pressure to Results. This analysis was restricted to patients of general practitioners who had been followed for at least 12 months. The placebo (N = 204) and active treatment (N = 217) groups had similar characteristics at randomization. At one year, the difference in sitting pressure between the two treatment groups was 10 mmHg systolic and 4 mmHg diastolic. Fewer patients remained on monotherapy in the placebo than in the active treatment group and on placebo the second and third line medications were started earlier. Nitrendipine tablets were discontinued in 10 patients on placebo and in 21 patients assigned to active treatment (P Conclusions. A significant blood pressure reduction can be achieved and maintained in older patients with isolated systolic hypertension followed by general practitioners. Whether this blood pressure reduction results in a clinically meaningful decrease of cardiovascular complications is under investigation. Keywords. Antihypertensive treatment, general practice, isolated systolic hypertension, randomized clinical trial.

Journal Article↗
PubMed1995

[Ipsilateral adrenalectomy in the surgical treatment of renal carcinoma].

OBJECTIVES: To assess the value of ipsilateral adrenalectomy during radical nephrectomy for the treatment of renal cell carcinoma as a function of preoperative computed tomography findings. METHODS: Between May 1985 and June 1994, 194 patients underwent radical nephrectomy for renal cell carcinoma in our institution. Preoperative radiological reports and postoperative pathological reports were reviewed for 185 patients. RESULTS: 148 patients underwent abdominal computed tomography before surgery. 94 adrenalectomies were performed in this group of patients. None of the 77 patients in whom computed tomography showed a normal adrenal gland had adrenal metastasis on the definitive histological examination. 17 patients had an adrenal mass on computed tomography, 3 of which proved to be neoplastic. Preoperative CT had a sensitivity of 100%, a specificity of 82%, a positive predictive value of 18% and a negative predictive value of 100%. The 185 files reviewed included 114 adrenalectomies, including 4 adrenal glands invaded by renal cell carcinoma (3.5%). In these 4 cases, the smallest diameter of the renal tumour was 4 cm and the minimum pathological stage was T3. CONCLUSIONS: It therefore appears justified not to perform adrenalectomy during nephrectomy, in the presence of a renal tumour and negative adrenal computed tomography.

Adenocarcinoma↗
PubMed1994

The role of transforming growth factor beta 1 in the fibroblastic reaction associated with rat colorectal tumor development.

Many tumors are surrounded by a highly fibrous stroma composed of fibroblasts and extracellular matrix. This desmoplastic response has been suggested to both inhibit and favor tumor progression. The present study deals with the effects of tumor cells on the fibroblastic reactions they cause and relates this to progression or regression of tumors. Two rat colon carcinoma cell lines, one which develops progressive tumors when injected s.c. in syngeneic animals (PROb cell line) and the other which develops regressive tumors in similar conditions (REGb cell line), were compared by the fibroblastic reaction which they cause. Comparative histological analysis of progressive and regressive tumors developed by the two cell lines showed a significant but opposite response of fibroblastic compartment. The progressive tumor nodules were observed to grow within a loose tissue, whereas the regressive tumor cells were surrounded by a fibrous capsule. Immunohistological labelings revealed the presence of alpha-smooth muscle actin-positive myofibroblasts during the tumor expansion, while these specific cells disappeared during the tumor regression. Immunostainings of transforming growth factor beta 1 showed an increasing staining of the progressive tumor cells during tumor development but a slight expression by tumor cells and stroma during the tumor regression. This growth factor was demonstrated to facilitate initial steps of the tumor progression by addition of active transforming growth factor beta 1 at the time of s.c. injection of PROb cells in syngeneic rat models. In vitro experimental analysis with the use of neutralizing antibody showed that active transforming growth factor beta produced by the progressive cells inhibited fibroblast proliferation and facilitated their differentiation into myofibroblasts. Since the number of myofibroblasts increased with time in progressive tumors, their presence may constitute a potential growth advantage for tumor growth. In contrast, our results indicated involvement of platelet-derived growth factor-like protein(s) in fibroblast proliferation under the control of regressive cells and the presence of an important sheath of alpha-smooth muscle actin-negative fibroblasts in regressive tumors may support a role for this growth factor in vivo. Thus, the ability of tumor cells to produce or induce the production of transforming growth factor beta or platelet-derived growth factor may give rise to a specific fibroblast reaction, which in turn may determine consequent tumor evolution.

Actins↗
PubMed1994

Comparative effect of calcium hydroxide and hydroxyapatite on the cellular activity of human pulp fibroblasts in vitro.

When, in vivo, calcium hydroxide [Ca(OH)2] or hydroxyapatite are used as dental pulp-capping agents, a reparative dentine bridge is observed. New hard tissue is formed directly on the hydroxyapatite, whereas a characteristic necrotic area appears under Ca(OH)2. The differing pulpal reactions to these two capping agents suggest differing cell responses. After isolation and selection of human pulp fibroblasts in vitro, the cells were characterized by their morphology, their high alkaline phosphatase specific activity, and their synthesis of type I and III collagens and fibronectin. They were then incubated in the presence of either hydroxyapatite (1 mg/ml) or Ca(OH)2 (0.8 mg/ml). With Ca(OH)2, the cells exhibited dramatical alterations in morphology, DNA synthesis, alkaline phosphatase activity and protein synthesis, in accordance with the necrosis observed in vivo. With hydroxyapatite, phagocytic activity of pulpal fibroblasts toward hydroxyapatite particles (< 10 microns) was seen. As a consequence, DNA synthesis was affected. This inhibitory effect was not due to cell damage, as demonstrated by increased [3H]-proline and [3H]-leucine incorporation by the cells. There was also an inhibitory effect of hydroxyapatite on alkaline phosphatase activity, suggesting that the pulp fibroblasts were not in a differentiation stage. In conclusion, compared to the effects of Ca(OH)2 on human pulp fibroblasts, these data are consistent with the biocompatibility of hydroxyapatite previously described in vivo and testify to the occurrence of a biological response elicited by this synthetic biomaterial.

Adolescent↗
PubMed1992

High and low affinity receptors for human interleukin for DA cells/leukemia inhibitory factor on human cells. Molecular characterization and cellular distribution.

Radioiodinated recombinant human interleukin DA (HILDA)/leukemia inhibitory factor (LIF) purified from conditioned medium of Chinese hamster ovary transfected cells enabled the identification of specific receptor sites on a variety of human cell types. Using low concentrations (up to 500 pM) of the ligand iodinated at a high specific radioactivity, high affinity receptors (equilibrium dissociation constant Kd in the range of 30-100 pM) were first demonstrated. They were expressed at low levels by human peripheral blood monocytes but not by lymphocytes, NK cells, granulocytes, and platelets. The myelomonocytic cell line THP1 as well as the T lymphoma cell line HSB2 and the lymphoblastoid B cell line DAB were also receptor-negative. In contrast, most of the non-lymphoid tumoral cell lines tested, including melanomas, neuroblastomas, and carcinomas, expressed high affinity HILDA/LIF receptors at variable levels (Bmax from 20 to 600 sites/cell). The kinetics of HILDA/LIF high affinity binding to the choriocarcinoma JAR cell line were characterized at 4 degrees C with association and dissociation rate constants of k1 = 2.2 10(9) M-1 min-1 and k-1 = 0.0084 min-1, respectively, corresponding to a steady-state dissociation constant k1/k-1 = 3.8 pM. The subsequent use of higher concentrations of HILDA/LIF labeled at a lower specific radioactivity enabled the identification of a low affinity component on several cell lines (Kd in the range of 1-4 nM; Bmax from 1,000 to 5,000 sites/cell). On JAR cells, this low affinity component was characterized by association and dissociation rate constants at 4 degrees C of k1 = 7.3 10(7) M-1 min-1 and k-1 = 0.19 min-1, respectively (k-1/k1 = 2.6 nM). Affinity cross-linking of HILDA/LIF to JAR cells showed two cross-linked species under both reducing and nonreducing conditions corresponding to receptor species of 120 and 250 kDa, respectively. Whereas both bands had similar intensities under high affinity conditions, the higher band predominated under low affinity conditions. Our data suggest that the 250-kDa chain could constitute the low affinity binding component whereas the association of both 250- and 120-Da subunits would form the high affinity structure.

Animals↗
PubMed1992

Mechanism of action of maternal serum on the interleukin2 receptor expression.

Neoplastic Jurkat cells were submitted to a PHA stimulation test after a preincubation in maternal or nulliparous serum (10% dilution). The Il2R expression was significantly downregulated among maternal serum treated cells. Retroplacental serum was significantly more inhibitive than peripheral maternal serum (P less than 0.01). The maternal IgG fractions and mostly the retroplacental IgG fraction proved to contain a factor mainly responsible for the Il2R expression inhibitive property. The molecular mechanism of this phenomenon was further studied. It was shown that H7 (acting as a protein kinase inhibitor) could not influence the Il2R modulation. E.G.T.A., a calcium chelator, was not able to interfere with the inhibitive influence of maternal serum. It was suggested that the maternal serum mediated inhibition of the IL2R expression is not influenced by the hydrolysis of membrane bound phosphatidyl inositol. In contrast, pertussis toxin markedly enhanced, in a dose dependent way, the suppressive influence of maternal serum as compared to nulliparous serum. At low concentrations, pertussis toxin lost its stimulating property and retained its ability to ADP ribosylate the alpha subunit of G proteins inducing a release of adenylcyclase mediating cAMP synthesis. This mechanism has been further studied by the addition of dbc AMP or dbc GMP to Jurkat cells preparations stimulated by PHA. dbc AMP, in a dose-related way, induced a downregulation of the IL2R expression of stimulated neoplastic cells preincubated in nulliparous or maternal serum. dbc GMP did not influence the IL2R expression in the same experimental conditions. The maternal serum mediated cells showed the most pronounced IL2R inhibition. Finally, it was shown that the cAMP synthesis by PHA stimulated Jurkat cells was upregulated in a dose dependent way, after a previous cellular incubation in progressive concentrations of maternal serum. In contrast, among nulliparous serum pretreated cells, cAMP synthesis remained significantly lower, after a lectin stimulation, as compared to the cAMP production derived from retroplacental serum treated and stimulated cells. Taken together, these experiments suggest that the maternal serum dependent suppression of the IL2R expression is related to a protein G stimulation followed by an enhanced cAMP synthesis.

Calcium↗
PubMed1991

Modulation of the HLA class II antigen at a molecular level by maternal serum among cord blood cells and unrelated lymphocytes.

A retroplacental serum factor responsible for the downregulation of the MHC class II antigen expression has been described [1]. We found that maternal serum had the same property. The HLA class II modulating activity is however diminished in the presence of maternal serum as compared to retroplacental serum suggesting that the IA like inhibiting factor is released at the fetomaternal interface. After a 3-day incubation period of unrelated lymphocytes and mononuclear cord blood cells in a maternal serum pool, it was shown that the HLA Dr, the HLADp, and more significantly, the HLADq molecules were modulated. This phenomenon was more pronounced among cord blood cells. When third party lymphocytes and mononuclear cord blood cells were stimulated by Candidine or unrelated mononuclear cells in the presence of retroplacental serum, only the cellular subpopulation belonging to the CD4+ subset showed an HLADq downregulation. The molecular constituents of the MHC class II antigen expression characterizing cells belonging to other subsets remained unchanged. When the same stimulation assay was performed in the presence of a control medium (nulliparous serum), we found no changes in the MHC class II molecular constituents. When unrelated mononuclear cells and mononuclear cord blood cells were PHA stimulated in the presence of maternal and nulliparous serum, the HLADq expression of the CD8+ subset showed a significant downregulation in the maternal serum mediated stimulation assay as compared to the control stimulation test. The molecular expression of the HLA class II antigen related to the other subpopulation (CD4+, CD3+) stimulated by a mitogenic lectin remained unchanged. It is suggested that these molecular MHC class II modulations are due to a factor included in the maternal IgG reaction. Retroplacental IgG contains the highest concentration of this factor.

Anti-Bacterial Agents↗
PubMed1991

Cellular activity of osteoblasts in the presence of hydroxyapatite: an in vitro experiment.

The use of synthetic calcium phosphate as bone substitute calls for the knowledge of the influence on adjacent cells. Effects on monocytes, macrophages, synovial cells and fibroblasts have been largely described in vivo and in vitro but few data are available as concerns osteoblast responses. The present experiments tested the activity of MC3T3-E1, ROS 17/2.8 and mouse calvaria cells cultured in the presence of hydroxyapatite powders. The three osteoblast-like cells were shown to phagocytoze the calcium phosphate particles. As a consequence, they exhibit reduced cell growth and alkaline phosphatase activity. This response was different when compared with other cell types. The osteogenetic function of osteoblastic cells could be involved in these specific effects of hydroxyapatite.

3T3 Cells↗
PubMed1991

Modulation of B cell stimulation by maternal serum.

Anti-IgM stimulation of B cells is decreased in the presence of maternal serum as compared to control media. This inhibiting influence of maternal serum is observed during the priming of the B cells. The progression of B cells into cellular proliferation was not influenced by maternal serum. At the level of the immunoglobulin secretion, the influence of maternal serum was also shown. A significant down regulation of the IgM, no change of the IgG production, and an enhanced secretion of IgA and IgE was demonstrated in the presence of maternal serum as compared to control media. It has been suggested that the maternal IgG fraction contains a molecule partly responsible for these changes. Furthermore, the CD23 antigen is increased when B cells are stimulated in the presence of a pool of maternal IgG. All the findings concerning maternal IgG were more pronounced when retroplacental IgG was used instead of peripheral maternal IgG. This observation suggests that the factor responsible for the B cell changes is released at the fetomaternal interface.

Antibodies, Anti-Idiotypic↗
PubMed1991

[Causal relations of occupational psychiatric disability].

This article discusses a problem that is relatively common in psychiatric practice, but almost non existent in the literature i.e., an occupational disability arising from a psychological trauma. This inquiry focuses on an area in which millions of dollars a year are at stake. Legislative and administrative authorities are increasingly demand that psychiatrists define objective criteria on which legislators can base decisions in contentious cases. What is the connection between the trauma and the current disability, and what is the risk of reoccurrence? Will the employee be able to resume his or her former duties? It quickly becomes clear that clinical, administrative and legislative realities are often incompatible. This article will therefore provide an overview of the subject in a historical perspective, and to orient the reader, will briefly describe the legislative context in the US and Quebec, as well as the role of the expert in assessing causality. We will attempt, by means of an overall conceptual model, to provide a synopsis of the usual procedure in this type of expert assessment.

Disability Evaluation↗
PubMed1990

Modulation of the HLA class II antigen at a molecular level by maternal serum.

The recent immunological literature has described the existence of a retroplacental serum factor being responsible for the downregulation of the MHC Class II antigen expression. In this report, the same property has been found in peripheral maternal serum. The HLA Class II modulating activity is however diminished in the presence of peripheral maternal serum as compared to retroplacental serum suggesting that the IA like inhibiting factor is released at the fetomaternal interface. After a three-day incubation period of unrelated lymphocytes in a maternal serum pool, it was shown that the HLA Dr., the HLA Dp., and more significantly, the HLA Dq. molecules were modulated. When third party lymphocytes were stimulated by Candidine or unrelated mononuclear cells in the presence of retroplacental serum, only the cellular subpopulation belonging to the CD4+ subset showed an HLA Dq. downregulation. The molecular constituents of the MHC Class II antigen expression characterizing cells belonging to other subsets remained unchanged. When the same stimulation assay was performed in the presence of a control medium (nulliparous serum), no changes concerning the MHC Class II molecular constituents were observed. When unrelated mononuclear cells were PHA stimulated in the presence of maternal and nulliparous serums, the HLA Dq. expression of the CD8+ subset showed a significant downregulation in the maternal serum mediated stimulation assay as compared to the control stimulation test. The molecular expression of the HLA Class II antigen related to the other subpopulations (CD4+, CD3+) stimulated by a mitogenic lectin remained unchanged. It is suggested that these molecular MHC Class II modulations are due to a factor included in the maternal IgG reaction. Retroplacental IgG contains the highest concentration of this factor.

Down-Regulation↗
PubMed1989

Chemical changes in hydroxyapatite biomaterial under in vivo and in vitro biological conditions.

The introduction of a synthetic calcium phosphate into a biological environment is likely to result in surface-mediated chemical events. On the basis of such an assessment, we studied the chemical changes occurring in the mineral after exposure of a synthetic hydroxyapatite ceramic to both in vivo (implantation in human) and in vitro (cell culture) conditions. A small amount of the material was phagocytized but the major remaining part behaved as a secondary nucleator as evidenced by the appearance of a newly formed mineral. Morphologically, the newly formed mineral appeared as tiny crystals precipitated and grown from the surface of the initial synthetic crystals. The density of the additional mineral increased from the periphery to the core of each biomaterial aggregate. Chemically, it was identified by IR spectroscopy as a carbonated apatitic mineral. We propose that the adsorption of biomolecules could inhibit precipitation, accounting for the increasing amount of precipitate from the periphery to the core of the aggregates.

Adult↗