[The evolutionary development of the jaws and dentition]. / De evolutie van het tandkaakstelsel.

The development of the jaws and dentition during half a billion years of evolution is described in broad lines and two theories regarding the origin of the dentition are discussed in detail. It is highly likely our dentition developed from dermal ossification 'denticles' originally protecting, in particular, the head of primitive extinct vertebrates. Simple, at first tubercular, later conical teeth developed into complex tooth and molar forms, especially in mammals. Special attention is given to the development of molar cusps. The process of continuous replacement of the dentition is also discussed in more detail.

A novel class of aromatic vitamin D analogs.

Vitamin D analogs in which the triene moiety is replaced by an aromatic ring have been synthesized and their ability to bind to the vitamin D receptor investigated.

Diastereoselective synthesis, binding affinity for vitamin D receptor, and chiral stationary phase chromatography of hydroxy analogs of 1,25-dihydroxycholecalciferol and 25-hydroxycholecalciferol.

A series of analogs of 1,25-dihydroxycholecalciferol and 25-hydroxycholecalciferol were obtained with an additional hydroxyl in the aliphatic side chain at carbon atom C-24. These analogs were synthesized by direct and diastereo-selective alpha-hydroxylation of enolates derived from respective vitamin D esters using Davies chiral oxaziridines. The use of (+)-(2R,8aS)-(8, 8-dichlorocamphoryl)sulfonyl oxaziridine resulted in (R) stereochemistry of the new asymmetric center for both series of analogs. Similarly, (-)-(2S,8aR) oxaziridine gave (S) analogs. The diastereomeric purity of hydroxy analogs was determined by high-performance liquid chromatography on a chiral stationary phase. High diastereopurity of hydroxylation of vitamin D esters was obtained without the use of any chiral auxiliary. The binding affinity of (24R)-1,24,25-trihydroxycholecalciferol for the calf thymus intracellular vitamin D receptor was one order of magnitude higher than that of the respective (24S)-diastereomer.

Convergent synthesis, chiral HPLC, and vitamin D receptor affinity of analogs of 1,25-dihydroxycholecalciferol.

A series of analogs of 1,25-dihydroxycholecalciferol was obtained with an additional chiral center at the terminus of the aliphatic side chain (C-25). The analogs were obtained from (+)-(R)- and (-)-(S)-2-methylglycidols, by opening of the oxirane ring with the carbanions derived from vitamin D C23a,24- or C22-sulfones. The diastereomeric purity of the analogs was determined by high-performance liquid chromatography on a chiral stationary phase. The binding affinity of analogs for the calf thymus intracellular vitamin D receptor (VDR) was two orders of magnitude lower than that of the lead compound of this group, 24a,24b-dihomo-1,25-dihydroxycholecalciferol, and it was comparable to the affinity of analogs of 24-nor-1,25-dihydroxycholecalciferol. However, a twofold difference was observed for analogs diastereomeric at C-25 in their affinity for VDR. The diastereodifferentiation of the binding affinity was found to be specific for vitamin D vicinal 25,26-diols as it disappears for analogs where 26-hydroxyl, neighboring the C-25 chiral center, is replaced with methyl.

Synthesis and in vitro evaluation of side chain-unsaturated analogs of 24a,24b-dihomo-1,25-dihydroxycholecalciferol.

A synthesis and an in vitro evaluation of side chain-unsaturated analogs 3 and 4 of 24a, 24b-dihomo-1,25-dihydroxycholecalciferol (1) are described, Novel C23a, 24-vitamin D synthons (sulfone 10 and aldehyde 11) were used for the synthesis of analog 4 and for the efficient preparation of the parent compound 1. The synthetic approach developed allows the use of easily available side chain fragments, such as oxirane 12 or Wittig reagent 15 for the preparation of compound 1 and analog 4, respectively. Introduction of a 24aE double bond results in a selective, 1000-fold increase in the binding affinity of analog 4 for the vitamin D receptor, compared to the affinity of 1, whereas the affinity of 4 for the vitamin D-binding protein and the activity in stimulating the differentiation of human promyelocytic leukemia HL-60 cells remained largely unchanged.

Reproductive history of mothers of children with solitary, nonsyndromic cleft lip and/or palate.

The reproductive history was studied to evaluate if the three types of solitary, nonsyndromic clefts: cleft lip (CL), cleft lip and palate (CLP), and cleft palate (CP) are homogeneous entities. Occurrence of fetal loss, maternal health, and drug consumption of the mother during the pregnancy were compared in cases involving three types of clefts. Data was gathered from 87 children with clefts, 55 males and 32 females. Spontaneous abortions and vaginal bleeding were found to occur significantly more often in the (older) mother of a CLP child. This suggests that the factors involved in the etiology of CLP differ from the factors involved in CL and CP. Therefore, grouping of data of the three types of clefts in studies on the etiology should be avoided.

The effect of duration and magnitude of tensile mechanical forces on sutural tissue in vivo.

Orthodontic springs were placed across the interparietal suture in twenty 30-day-old male Wistar rats, in order to study the effect of tensile forces on the initial biological response of sutural tissues. Five groups of different force duration and magnitude were used: a 6 hours (h), 0 mN group; 6 h and 24 h, 50 mN groups; and 6 h and 24 h, 100 mN groups. One group of four animals served as a control. The animals were injected with tritiated proline 3 hours prior to the end of the experiment. Undecalcified 5 microns sections were used for (enzyme) histology and autoradiography in order to quantify several morphometric variables. The data were analysed with multivariate analysis of variance and contrast calculations. Application of the springs led to significant sutural widening within 6 hours. The concentration of fibroblasts in the suture also increased significantly within 6 hours. The volume of the suture and the incorporation of 3H-proline in the fibrous part of the suture and in the osteoid along the sutural bony edges were significantly increased after 24 hours of force. In general, force duration had a greater impact on histological events than force magnitude.

Dental anomalies in patients with familial and sporadic cleft lip and palate.

Based on the frequency of occurrence of cleft lip and palate (CLP) in a family, a distinction has been made between familial and sporadic CLP. It was presumed that the genetic predisposition in familial CLP is high, while in sporadic CLP environmental factors play an important role. This study describes the possible relationship between the incidence of dental anomalies and the genetic predisposition of CLP in both the deciduous and permanent dentition. Dental anomalies were studied in 100 CLP patients and 38 control subjects. Neither the number of dental anomalies, nor the numbers of missing and supernumerary teeth differed significantly between familial and sporadic cases. A comparison between subjects with and without CLP showed a significant difference in the morphology of the dentition of the upper jaw. This difference was quantitative rather than qualitative. This study indicates a direct relationship between cleft formation and formation of the teeth, irrespective of the genetic predisposition and the severity of the cleft (i.e. uni- or bilateral).

Sutures and forces: a review.

This review gives a description of the biologic significance of craniofacial sutures with respect to growth and to growth corrections. Sutural growth and its regulation are discussed briefly. Morphogenesis of sutures, sutural morphology, both microscopic and macroscopic, the structure and function of the sutural periosteum and secondary cartilages, and the biochemical composition of sutures are described. Furthermore, in vivo and in vitro experiments, including transplantation experiments, are discussed. The relationship between extrinsic mechanical forces and the resulting tissue responses in sutures is given special attention. The present article describes the state of our knowledge on the interaction between sutures and forces, and indicates problems that need to be investigated.

Tissue changes in the rabbit periodontal ligament during orthodontic tooth movement.

In this (semi) quantitative animal study the reaction of the periodontal ligament (PDL) to experimental tooth movement is described. To this end, rabbit first incisors were moved sideways with helical torsion springs for periods varying from 3-24 hours. The initial force of the springs was 50 gf. The histomorphology of the PDL was studied in 5 microns thick plastic sections. Comparison with control animals and animals wearing passive springs showed that tooth movement leads to an increased trauma in the PDL within only a few hours. This trauma is characterized by hyalinization, tears and ruptures in the fibres and blood vessels, and by the presence of extravascular erythrocytes and pyknosis. Tissue damage significantly increased with time. After 24 hours of tooth movement, the PDL fibers are compressed or stretched in 68% of the sections and the blood vessels in the PDL are compressed or stretched in 62% of the sections. Even in the controls, more than 15% of the sections displayed slightly stretched or compressed fibers, and about 10% showed slightly compressed or stretched blood vessels. This indicates that some damage is regularly present in a normally functioning PDL. Increases in the percentage of sections with blood vessel compression are found in all groups wearing passive springs, especially after 6 hours. A high concordancy in compression and tension patterns of blood vessels and fibers is present in 83% of the sections. Pyknotic cells are practically confined to areas with compressed PDL fibers in rabbits wearing active springs. Extravascular erythrocytes were found in sections with all types of fiber patterns. A significant majority of extravascular erythrocytes, however, was found in areas with compressed fibers.

Patterns and relationships of plasma calcium, protein and phosphorus during the egg laying cycle of the fowl and the effect of dietary calcium.

In 29 domestic hens, four blood samples were collected during the period of egg formation, at time points representing different metabolic stages. Plasma concentrations of total calcium, total phosphorus, inorganic phosphorus and total protein were measured, and the effect of adding oyster shell particles to a standard laying diet was investigated. Analyses of covariance were made and correlations between the plasma characteristics were calculated. The following were significantly correlated: total and inorganic phosphorus, calcium and total phosphorus, and calcium and protein. Each of the four characteristics showed a significant decrease during egg formation. Inorganic phosphorus reached a peak 15 h after ovulation, probably related to medullary bone resorption. Plasma total phosphorus differed significantly between chickens. Addition of oyster shell to the diet did not affect the concentration or the pattern of the plasma characteristics during egg formation and did not reduce calcium mobilisation from medullary bone during shell formation.

Medullary bone matrix formation, mineralization, and remodeling related to the daily egg-laying cycle of Japanese quail: a histological and radiological study.

A model is presented concerning the remodeling of medullary bone during the egg-laying cycle of hens. This model is partly based on earlier results that showed that the active period of medullary bone resorption that produces part of the calcium needed for the eggshell coincides with the period of medullary bone matrix formation. It was hypothesized that mineralization of this matrix takes place during the subsequent inactive period. The present study examines this model. The medullary bone matrix volume, regardless of the degree of mineralization, is quantified in quail hens at four time points during the egg-laying cycle. No significant changes in the medullary bone volume (i.e., matrix and bone) during the egg-laying cycle were found, implying that matrix formation and bone resorption are kept in balance within a time interval of only a few hours. In the radiological part of this study the whole body retention (WBR) of 99mTc(Sn)MDP is used as a measure of the amount of low calcium medullary bone matrix formed during the egg-laying cycle. This use of 99mTc(Sn)MDP is justified by an autoradiographic experiment that showed that 99mTc(Sn)MDP actually labels newly formed medullary bone. Localization of the radioactive label showed a high positive correlation with the localization of fluorescent tetracycline labels in the medullary bone. From 4 to 22 hours after ovulation, the amount of medullary bone matrix increases linearly in quail hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Parathyroid hormone responses to calcium stress during eggshell calcification.

PTH bioactivity during the egg-laying cycle of the chicken has been measured by the cytochemical bioassay for PTH. During the period of eggshell calcification, PTH bioactivity is elevated. After completion of the shell the plasma PTH falls to a low level but is slightly raised again 2 h after ovulation. These results indicate that changes in bioactive PTH play an important role in the calcium metabolism of the chicken during this physiological calcium stress.

Changes in activity of chicken medullary bone cell populations in relation to the egg-laying cycle.

Osteoblastic and osteoclastic activity was studied in avian medullary bone in vivo. During the active period of eggshell calcification, medullary bone active resorption surface increased ninefold. This correlated with a sevenfold increase in the percentage of active osteoclasts. Osteoblast activity is also increased during the active period, as demonstrated by a twofold increase in the active osteoblastic surface. These findings and our observation that the medullary bone volume remains the same (+/- 13%) whether the eggshell is being formed (active period) or not (inactive period) led to the conclusion that the activities of osteoblasts and osteoclasts rapidly return to balance.