The influence of three endodontic sealers on bone healing: an experimental study.

BACKGROUND: The aim of this experimental study is to assess the bone healing phenomenon produced in the presence of 3 dental materials used for the root canal obturation. MATERIALS AND METHODS: The biocompatibility of 3 endodontic sealers (a self-curing epoxy resin - AH Plus, a dual cure urethane dimethacrylate resin - RealSeal and a new dual cure endodontic hydroxyapatite based filling material) was investigated after intra-osseous implantation of the materials in rats' calvaria. Tissue reaction was studied at 2, 4, 6, 8, 10 and 12 weeks after implantation using calibrated image retrieval by Olympus. We took into consideration the presence of inflammatory cells (polymorphonuclear leukocytes, macrophages, plasma cells, lymphocytes and giant cells) and classified the aspects of the histological samples according to the following scale: 0 - no inflammation, 1 - mild, isolated inflammation, 2 - moderate, localised inflammatory reaction, 3 - severe, diffuse and intense inflammatory reaction. RESULTS: The inflammatory reaction was present at the 6 intervals for all the tested materials, but a decrease of the inflammatory infiltrate, statistically significant, until extinction for all tested materials was observed at the end of the experimental period. The reaction of bone tissue recovery was most intense in the case of the control area. Lower intensity osteogenesis phenomenon was observed in case of all 3 tested sealers at the end of the experimental period. CONCLUSIONS: Biocompatibility and bone healing induction of the new hydroxyapatite based endodontic filling material is comparable to other commercial materials, AH Plus and RealSeal.

Oral health status among schoolchildren in Romania, 1992.

In Romania, systematic information on the occurrence of oral diseases in children is scarce. The purpose of the present study was to describe the prevalence and the pattern of dental caries in schoolchildren, and to use the data to provide a baseline for planning and evaluation of oral health care. A national sample of children at grade 1 (n = 729) and grade 6 (n = 660) was chosen consistent with the WHO pathfinder principle. Clinical examinations were carried out according to the recording system for the Danish Municipal Dental Service and the following results were obtained. In children of grade 1 (7-yr-olds) the prevalence proportion of caries in primary teeth was 86% and in permanent teeth 39%. The mean caries indices were 11.4 defs and 1.3 DMFS. At grade 6 (12-yr-olds) the prevalence proportion of caries in primary teeth was 17% and in permanent teeth 90%. The mean caries experience was 0.8 defs and 6.5 DMFS, and a mean of 4.1 DMFT was observed. In both groups, the D-component of the caries index was dominant. The children were also classified by caries severity zone. At grade 1, 61% had a very severe pattern of caries in the primary teeth, i.e. caries in pits/fissures, proximal surfaces, smooth surfaces, and incisors. Forty-three percent of the children at grade 6 showed this pattern in permanent teeth. In Romanian schoolchildren the present level and pattern of dental caries are most severe and the implementation of oral health promotion and prevention at the community level is urgently needed.

The modulation of circulating parathyroid hormone immunoheterogeneity in man by ionized calcium concentration.

Twenty normal individuals received 2-h iv infusions of CaCl2 and Na2 ethylenediamine tetra-acetate, with sampling every 15 min. PTH was measured by means of an intact hormone assay (I) and two carboxylterminal assays structured to react mostly with mid (M) or late (L) carboxylterminal fragments. A mathematical model was used to fit the sigmoidal relationship between ionized calcium (CA++) and PTH values. The influence of Ca++ on circulating PTH immunoheterogeneity was assessed via changes in L/I, M/I, and M/L ratios. Results are reported as means +/- SD. Response to hypocalcemia was highest with M (57.8 +/- 26.4 pmol/L, P less than 0.005 vs. L or I) and higher with L (20.1 +/- 5.6 pmol/L; P less than 0.0005 vs. I) than with I (14.1 +/- 6.4 pmol/L). L/I, M/I, and M/L decreased from 2.43 +/- 0.56 to 1.54 +/- 0.19 (P less than 0.0005), 8.44 +/- 2.38 to 4.36 +/- 4.07 (P less than 0.0005), and 3.49 +/- 0.71 to 2.86 +/- 0.76 (P less than 0.005), respectively, during Na2 ethylenediamine tetra-acetate infusion. Nonsuppressible PTH was again higher with M (13.7 +/- 4.8 pmol/L; P less than 0.0005 vs. L or I) and higher with L (2.8 +/- 0.7 pmol/L, P less than 0.0005 vs. I) than with I (0.5 +/- 0.3 pmol/L). L/I, M/I, and M/L ratios increased from 2.47 +/- 0.97 to 5.35 +/- 2.09 (P less than 0.0005), 8.90 +/- 3.10 to 29.56 +/- 14.89 (P less than 0.0005), and 3.62 +/- 0.90 to 5.30 +/- 1.91 (P less than 0.005) during CaCl2 infusion. The set-point for PTH stimulation by calcium was similar for M (1.15 +/- 0.035 mmol/L) and L (1.175 +/- 0.041 mmol/L) but significantly higher with the I assay (1.184 +/- 0.31 mmol/L; P less than 0.0005 vs. M). The M/I, L/I, and M/L ratio set-points were similar at 1.28 +/- 0.01, 1.27 +/- 0.01, and 1.29 +/- 0.02 mmol/L. Thus, even if proportionately more intact PTH and less carboxylterminal fragments are produced and secreted during hypocalcemia, the latter still predominate in the circulation. Furthermore, at high calcium values, secretion of fragments is less well inhibited than that of intact hormone. The lower secretion and higher ratio set-points suggest that the secretion and intracellular degradation of PTH have different sensitivities to inhibition by calcium.

Synthesis and biological activity profiles of atrial natriuretic factor (ANF) analogs.

Several analogs of the atrial natriuretic factor (ANF) were synthesized by the solid-phase method using the acetamidomethyl (Acm) group for sulfhydryl protection. The compounds were tested in a receptor binding assay using bovine adrenal zona glomerulosa cell membranes and in the rat diuresis/natriuresis assay. Substitution of tyrosine in position 116 of ANF(101-126) and of the analog [3-Mpr105]ANF(105-126)(3-Mpr = 3-mercaptopropionic acid) did not alter the biological activity profiles and, therefore, these two analogs in radioiodinated form will be useful for enzymatic degradation and clearance studies. Replacement of 3-mercaptopropionic acid with 2-mercaptopropionic acid in [3-Mpr105]ANF(105-126) resulted in an analog with very low potency in both assay systems, presumably as a consequence of the steric bulk and/or local conformational restriction produced by the methyl group attached to the alpha-carbon in position 105. The analog [3-Mpr105,Nva109]ANF(105-126)(Nva = norvaline) showed very low affinity in the receptor binding assay but displayed considerable diuretic/natriuretic activity. The obtained biological activity profiles suggest that in comparison with other ANF peptides the des-amino ANF(105-126) analogs may have a somewhat longer half-life in vivo, or alternatively, may indicate a more complex situation of ANF receptor or binding site heterogeneity.

Characterization, distribution and plasticity of atrial natriuretic factor binding sites in brain.

The [125I]iodotyrosyl derivative of atrial natriuretic factor [( 125I])ANF) apparently binds to a single class of high affinity sites in guinea pig brain membrane preparations. Ligand selectivity pattern reveals that the structural requirements of brain [125I]ANF binding sites are similar to those reported in most peripheral tissues. In vitro receptor autoradiographic studies demonstrate that the brain distribution of [125I]ANF binding sites is species dependent. In rat, high levels of binding are found in olfactory bulb, subfornical organ, area postrema, choroid plexus, and ependyma. In guinea pig, these regions are also enriched with [125I]ANF binding in addition to various thalamic nucleic, amygdala, hippocampus, and cerebellum. In monkey, high densities of sites are seen in the cerebellar cortex. This suggests that brain ANF receptor sites could mediate ANF effects related to the central integration of cardiovascular parameters, as well as other actions not associated with these systems. As in the periphery, it appears that brain [125I]ANF binding sites are associated with guanylate cyclase. Moreover, the density of [125I]ANF receptor binding sites is altered in certain brain regions in spontaneously hypertensive rats and in cardiomyopathic hamsters, demonstrating the plasticity of brain ANF receptors. Thus, ANF and ANF receptors are complementary facets of a new neurotransmitter-neuromodulator system present in mammalian brain.

Superactive analogs of the atrial natriuretic peptide (ANP).

Three analogs of the atrial natriuretic peptide ANP(105-126), lacking the N-terminal exocyclic peptide segment and containing 2-mercaptoacetic acid, 3-mercaptopropionic acid or 4-mercaptobutyric acid in place of the cysteine residue in position 105 of the peptide sequence, were synthesized by the solid-phase method. The resulting des-amino analogs showed 2 to 4 times higher diuretic/natriuretic activity than the most active natural ANP and displayed a potent hypotensive effect as well. All three analogs were relatively less potent in various in vitro bioassays and in a binding assay, indicating that their high activities in vivo may be due to resistance to enzymatic degradation and to reduced non-specific tissue adsorption. These compounds not only will serve as useful pharmacologic tools but also represent prototypes for the development of further reduced-size ANP analogs.

Synthesis and activity profiles of atrial natriuretic peptide (ANP) analogs with reduced ring size.

Three deletion analogs of the atrial natriuretic peptide, [desGly-120]-ANP(103-126), [desLeu119, desGly120]ANP(103-126) and [desGly118,120,-desLeu119]-ANP(103-126), were synthesized by the solid-phase method. Successive elimination of the non-functional residues in positions 120-118 of the peptide sequence resulted in a progressive potency reduction in the rabbit aorta assay, in the bioassay monitoring suppression of aldosterone secretion from bovine zona glomerulosa cells and in a binding assay based on displacement of radioiodinated ANP(101-126) from bovine zona glomerulosa cell membranes. The fact that the deletion analogs showed quantitatively different relative potencies in each of the three in vitro assay systems was interpreted as further evidence in support of the existence of two or more classes of ANP receptors or binding sites.

Radioimmunoassay of atrial natriuretic factor: human plasma levels.

A simple and sensitive radioimmunoassay procedure has been developed for the determination of atrial natriuretic factor (ANF) in human plasma. The rabbit antiserum was obtained from a commercial source. ANF was extracted from plasma using an octadecasilyl silica cartridge with a recovery of 78.7%. HPLC of the plasma extract showed the presence of one immunoreactive peak of ANF corresponding to its low molecular weight form. Plasma ANF in humans increased from 8.0 +/- 2.2 in upright position to 20.0 +/- 5.9 fmol/ml (n = 6) in downward position (p less than 0.005).

Discordant disappearance of bioactive and immunoreactive parathyroid hormone after parathyroidectomy.

The disappearance of plasma PTH after parathyroidectomy was assessed in patients with primary hyperparathyroidism and normal renal function, chronic renal failure or restored renal function (after transplantation). Plasma PTH levels were determined by renal cytochemical bioassay and by midregion and carboxyl-terminal RIAs. Baseline PTH levels were lower in each patient when assessed by bioassay than when determined by RIA, and the rate of hormone disappearance was faster when determined by bioassay than when measured by RIA. This difference was accentuated in chronic renal failure due to prolongation of the disappearance rates of midregion and carboxyl-terminal immunoreactivity. The half-life of bioassayable hormone in patients with chronic renal failure was prolonged less than 2-fold compared to the half-life in patients with normal or restored renal function. The results emphasize the discordance between levels of bioactive and immunoreactive hormone regardless of renal function, demonstrate that this discordance is augmented after acute reduction in circulating hormone, and show that it is further increased when kidney function is impaired. The studies also implicate extrarenal mechanisms as a major factor in the clearance of bioactive hormone in established renal failure.

Differential effects of GTP on the coupling of beta-adrenergic receptors to adenylate cyclase from frog and turkey erythrocytes. Application of new methods for the analysis of receptor-effector coupling.

A detailed comparison of the interaction of beta-adrenergic receptors with adenylate cyclase stimulation and modification of this interaction by guanine nucleotides has been made in two model systems, the frog and turkey erythrocyte. Objective analysis of the data was facilitated by the development of new graphical methods which involve the use of logit-logit transformations of percent receptor occupancy versus percent enzyme stimulation plots (coupling curves). Receptor-cyclase coupling in turkey erythrocyte membranes demonstrates a proportional relationship between receptor occupancy and adenylate cyclase activation and is unaffected by exogenous guanine nucleotides. By comparison, the proportional relationship of receptor occupancy and adenylate cyclase activation observed in frog erythrocyte membranes in the absence of guanine nucleotides is modified by the addition of exogenous guanine nucleotides such that a greater fractional enzyme stimulation is elicited by low receptor occupancy. Methodological criteria crucial for valid comparison of receptor occupancy and adenylate cyclase activity are delineated. In addition, the possible molecular mechanisms of receptor-cyclase coupling which might give rise to the coupling curves observed are discussed.

Simultaneous analysis of families of sigmoidal curves: application to bioassay, radioligand assay, and physiological dose-response curves.

Physiological and pharmacological studies of hormones, drugs, and neurotransmitters often generate families of sigmoidal dose-response curves. Optimally efficient data analysis should involve simultaneous description of all curves, rather than fitting each one individually. We have developed a general computerized method to describe the dose-response curves in terms of basal and maximal responses, ED50, and curve shape or steepness. This facile method permits rigorous statistical analysis, provides a basis for pooling of information from separate experiments, and allows one to test which characteristics are shared by various curves.