Induction of chemoresistance in HL-60 cells concomitantly causes a resistance to apoptosis and the synthesis of P-glycoprotein.

The appearance of multidrug-resistant (MDR) proteins or the acquisition of a defective apoptotic programme are major drawbacks in the treatment of cancers since both induce a resistance to classical chemotherapy. However, a link between the two mechanisms has not, as yet, been clearly established. In this study, HL-60 cells cultured in the continual presence of a sub-lethal dose of doxorubicin (dox; HL-60/Dox) were used as a model to study acquired chemoresistance. During the induction of chemoresistance, the appearance of a functional P-glycoprotein (P-gp), in addition to the expression of anti-apoptotic Bcl-2, Bcl-XL and pro-apoptotic Bax proteins was assessed. Parental cells which are sensitive to dox, have no P-gp activity and express Bcl-2 and Bax. After 4 weeks of treatment, a functional P-gp was detected in HL-60/Dox cells. In addition, the synthesis of Bcl-2 appeared to be replaced by Bcl-XL while that of Bax remained unchanged. These cells were also resistant to apoptosis induced by both P-gp and non-P-gp substrates. This inability to induce apoptosis could have resulted from the induction of the expression of the inhibitor of apoptosis protein (XIAP). Our data show that acquired chemoresistance could involve a parallel induction of P-gp and an impairment of the apoptotic pathway.

Production and characterisation of a monoclonal antibody specific for apoptotic bodies derived from several tumour cell lines.

We have recently shown that apoptotic bodies (apobodies) derived from rat colon carcinoma cell lines (PROb) after sodium butyrate (NaB) treatment were able to cure rats with induced peritoneal carcinomatosis ( [BOISTEAU] ). A specific immune response was assumed to be involved since the serum of cured rats contained antibodies specific for apobodies. In the present study, a mAb (clone 6E8) produced by immunisation of rats with apobodies strongly recognized apobodies but had little reactivity with parental tumour cell lines, as demonstrated by enzyme-linked immunosorbent assay (ELISA), immunostaining and flow cytometry. Immunoelectron microscopy showed that 6E8 mAb mainly stained the hyaloplasm or cytosol of apobodies. A protein was detected at 67 kDa by immunoprecipitation of apobodies with mAb, followed by immunoblotting, using serum of rats immunised with apobodies. The 6E8 mAb recognized apobodies derived from several rat or human colon cancer cell lines and a rat glioma cell line, regardless of the apoptosis stimulus used (NaB, staurosporine or UV). Our results clearly show that 6E8 mAb defines an epitope specifically generated during apoptosis, which suggests that the protein recognized may be involved in the molecular cascade of apoptotic cell death.

[The structure and ultrastructure of the pulp in Vipera aspis (Viperidae)]. / Structure et ultrastructure de la pulpe de Vipera aspis (Viperidae).

The present paper using classical and transmission electron microscopy brings the first data on the pulp of the fangs of Viperidae (poisonous serpents with terrestrial or semi-aquatic habits). The pulp of the fangs of Viperidae shows a poor collagen and fibroblast content and a high developed vascular system. The odontoblasts are polarized, with a high organelle content. The interconnections are constituted of lateral "gap junction" systems. At a late secretion stage, the odontoblastic processes show a poor cytoplasm, mainly constituted of microfilaments.

[Anomalies of enamel formation in subjects with maxillary clefts]. / Anomalies de formation de l'émail chez les sujets présentant des fentes maxillaires.

A structural and ultrastructural study of teeth located in the vicinity of maxillary cleft and teeth located outside the cleft region, was made in 12 cases, using correlated light microscopy, microradiography and SEM. All teeth directly involved in cleft process presented gross hypoplasia of the crown where the enamel surface was hypomineralized. Globular calcified masses of different radiodensity were seen on the hypomineralized enamel surface. The teeth located outside the cleft region presented less pronounced anomalies constituted by isolated or group microhypoplasia on hypomineralized enamel. The observation of enamel pearl was not pathognomonic of maxillary cleft.

[The structure, ultrastructure and physicochemical analysis of the hard dental tissues of the Viperidae]. / Structure, ultrastructure et analyses physico-chimiques des tissus durs dentaires des vipéridés.

The present study, using classical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, infrared spectroscopy, has shown the dental hard tissues of the fangs of Viperidae (poisonous serpents with terrestrial or semi-aquatic habits) to be constituted of: a calcified outer layer, 0.4 microns thick, made of very small needle-like crystals, randomly distributed. The calcified outer layer contains organic invaginations inducing pores at the surface and many collagen fibres incompletely mineralized, which may suggest enameloid. a calcified inner layer, in the wall of the poison canal. The calcified inner layer, 0.6 microns thick, is constituted of very small crystals, which are parallel to each other and perpendicular to the calcified outer layer. It might be the inner layer of enameloid, an orthodentine, whose tubules present a special lateral branching system resembling a fish bone. The TEM data, which show the dentine to be constituted of very small ill-defined crystals and incompletely mineralized collagen fibres are corroborated by chemical analyses which reveal a poorly mineralized apatite with high carbonate content.

Regional odontodysplasia: new histopathological data.

Light microscopy, microradiography, SEM and TEM of 4 tooth follicles in a 12-year-old caucasian girl presenting regional odontodysplasia showed widespread globular dentin, calcifications located in the enlarged pulp chambers, hypoplastic and hypomineralized enamel. Hypomineralized strands were sandwiched between two normal enamel layers, which indicates that amelogenesis, interrupted for a while, has once more become established. The enamel surface was covered with calcoglobules. Numerous rounded calcifications were scattered within the dental follicles. Some of these occurred in microfibrils (possibly oxytalan fibers), distinct from collagen fibers. Calcification of the sheath surrounding epithelial rests was a conspicuous feature. The fibroblasts in contact with calcifications developed numerous cytoplasmic extensions, which suggests that they may have assumed a phagocytosis behaviour.

[Dental enamel pearls: histopathological study]. / Les perles d'émail: étude histopathologique.

Enamel pearls are small rounded or egg-shaped nodules which most frequently develop in the furcation area of molars. They may consist of enamel only or enamel containing a small core of tubular dentin. They often sit upon strands of cementum or Tomes granular layer. Histologically, the enamel surface of enamel pearls resembles immature enamel and may be covered with cementum. Small calcoglobules presenting varying degrees of organization are often found related to enamel pearls. Some of them, which have the same radiodensity as the enamel of the pearl and of the affected tooth, may be considered as an enamel-type of calcifications. Others, which present a concentric structure revealed by a polarization cross when viewed between cross polars, may be similar to cementicles. All calcifications located in contact with enamel pearls or at a distance, from them are dystrophic calcifications.

Report on caries reduction in French schoolchildren 3 years after the introduction of a preventive program.

A combination of preventive methods have been used to reduce dental caries in children aged 7-8 at baseline, living in a non-fluoridated area in the West of France. The preventive program involved a daily supervised toothbrushing at school with 180 mg of fluoridated toothpaste, professional prophylaxis every 2 months with topical application of fluoride gel and reinforced motivation. The oral hygiene level was measured using the Silness-Löe plaque index and caries were recorded using the def and DMF surface indices, including incipient lesions. The 3-yr results showed a significant 52% plaque reduction in the test group compared with the control group. Caries reduction was significant at the 0.01% level: 44% for primary teeth and 60% for permanent teeth.

Enameloid in the teleost fish Lophius. An ultrastructural study.

The ultrastructural and chemical differences between mature enameloid and dentine in the teleost fish Lophius were demonstrated using transmission (TEM) and scanning (SEM) electron microscopy, X-ray diffraction analysis, electron diffraction analysis and electron microprobe analysis. An enameloid cap (about 50 micron thick) and a thin layer (1 micron thick) of collar enameloid were revealed in the scanning (SEM) and transmission (TEM) electron microscopes. Collar enameloid, structurally different from dentine both in SEM and TEM, proved to be less mineralized than the cap as revealed by electron microprobe analysis. The enameloid cap was seen to differ from dentine by (i) its electron density in TEM; (ii) the structural arrangement perpendicular to the underlying dentine, observed in SEM and TEM and corroborated by electron diffraction data, which showed a preferred orientation of enameloid crystallites; (iii) its higher F content decreasing gradually from the apex of the tooth to the junction with dentine and falling suddenly below this junction; and (iv) its lower Mg content. Establishment of a classification of enameloids is proposed, similar to that for dentines, in which selachian enameloid would be a reference standard.

Osteodentine and vascular osteodentine of Anarhichas lupus (L.).

TEM, SEM and X-ray diffraction analysis demonstrate the heterogeneity of the dentinal tissue on Anarhichas lupus, a vascular osteodentine. The disordered aspect of collagen fibres, incompletely mineralized (the periodical striation being still visible), explains the scattered distribution of crystallites since they are responsible for their arrangement. The low degree of mineralization revealed by the visible collagen striation is confirmed by X-ray diffraction analysis (the crystallinity of vascular osteodentine being much lower than that of the peripheral dental tissue) as well as by high resolution TEM, since no lattice planes could be observed. Osteodentine, supporting bone and proper bone have in common a mineral phase, more or less organized, different from the apatite system.