Jan-Paul van de Velde - Academia.edu (original) (raw)

Papers by Jan-Paul van de Velde

The Cleft Palate-Craniofacial Journal, 1992

SUMMARY Orthodontic springs were placed across the interparietal suture in twenty 30-day-old male... more SUMMARY 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

Acta morphologica Neerlando-Scandinavica

In this (semi) quantitative animal study the reaction of the periodontal ligament (PDL) to experi... more 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 ...

Journal de biologie buccale, 1988

Based on the frequency of occurrence of cleft lip and palate (CLP) in a family, a distinction has... more 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 gene...

The European Journal of Orthodontics, 1990

Orthodontic springs were placed across the interparietal suture in twenty 30-day-old male Wistar ... more 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.

The European Journal of Orthodontics, 1988

In this (semi)quantitative animal study the reaction of the gingival tissues to experimental toot... more In this (semi)quantitative animal study the reaction of the gingival tissues to experimental tooth movement is described and compared to the reaction in the periodontal ligament. To this end, rabbit first incisors were moved sideways with helical torsion springs for periods varying from 3–72 hours. The initial force of the springs was 50 gf. Comparison with control animals and animals wearing passive springs showed that tooth movement itself leads to trauma in the dentogingival area within only a few hours. This trauma is characterized by tears and ulcerations in the epithelium, by tears and ruptures in the fibres, by leukocytic infiltration and by the presence of extravascular erythrocytes. Between the incisors, however, a firm connective tissue septum, acting as a reinforcement to the dentogingival area, remains intact. Tissue damage significantly increases with time. After 72 hours of orthodontic force, however, the interdental papilla seems to have recovered to some extent. The histologic data of the dentogingival area in animals wearing active springs, were compared to those of the underlying periodontal ligament by multivariate analysis of variance. This analysis showed, that there are significant differences between the tissue reaction in the labial and palatal segments, and between the dentogingival and dentoalveolar areas. Furthermore, a close relationship was found between the damage to the fibres and the occurrence of extravascular erythrocytes and leukocytes. It was therefore concluded, that local tissue damage, characterized by rupture of fibres, leads to an inflammatory reaction in the gingiva and the periodontal ligament.

American Journal of Orthodontics and Dentofacial Orthopedics, 1988

This review gives a description of the biologic significance of craniofaciai sutures with respect... more This review gives a description of the biologic significance of craniofaciai 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.

Metabolic Bone Disease and Related Research, 1984

Osteoblastic and osteoclastic activity was studied in avian medullary bone in vivo. During the ac... more 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 (k 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.

ChemInform, 2010

A Novel Class of Vitamin D Analogues. Synthesis and Preliminary Biological Evaluation.-Five vitam... more A Novel Class of Vitamin D Analogues. Synthesis and Preliminary Biological Evaluation.-Five vitamin D analogues, e.g. (IV), are prepared in which the triene system and the A-ring are replaced by an aromatic ring. Generally the compounds demonstrate a high affinity towards the vitamin D receptor. The vitamin D analogues are relatively good binders.

Steroids, 1997

A synthesis and an in vitro evaluation of side chain-unsaturated analogs 3 and 4 of 24a,24b-dihom... more A synthesis and an in vitro evaluation of side chain-unsaturated analogs 3 and 4 of 24a,24b-dihomo-l,25dihydroxycholecalciferol (1) are described. Novel C23,,.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 I2 or Wittig reagent 15for the preparation of compound I and analog 4, respectively. Introduction of a 24aE double bond results in a selective, lO00-fold increase in the binding affinity of analog 4for 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.

Endocrinology, 1984

PTH bioactivity during the egg-laying cycle of the chicken has been measured by the cytochemical ... more 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.

Current Pharmaceutical Design, 2000

Chirality, 1999

A series of analogs of 1,25-dihydroxycholecalciferol was obtained with an additional chiral cente... more 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 C 23a,24-or C 22-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.

Chirality, 1999

A series of analogs of 1,25-dihydroxycholecalciferol and 25hydroxycholecalciferol were obtained w... more A series of analogs of 1,25-dihydroxycholecalciferol and 25hydroxycholecalciferol were obtained with an additional hydroxyl in the aliphatic side chain at carbon atom C-24. These analogs were synthesized by direct and diastereoselective ␣-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)-1,24,25trihydroxycholecalciferol for the calf thymus intracellular vitamin D receptor was one order of magnitude higher than that of the respective (24S)-diastereomer. Chirality

The Cleft Palate-Craniofacial Journal, 1992

SUMMARY Orthodontic springs were placed across the interparietal suture in twenty 30-day-old male... more SUMMARY 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

Acta morphologica Neerlando-Scandinavica

In this (semi) quantitative animal study the reaction of the periodontal ligament (PDL) to experi... more 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 ...

Journal de biologie buccale, 1988

Based on the frequency of occurrence of cleft lip and palate (CLP) in a family, a distinction has... more 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 gene...

The European Journal of Orthodontics, 1990

Orthodontic springs were placed across the interparietal suture in twenty 30-day-old male Wistar ... more 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.

The European Journal of Orthodontics, 1988

In this (semi)quantitative animal study the reaction of the gingival tissues to experimental toot... more In this (semi)quantitative animal study the reaction of the gingival tissues to experimental tooth movement is described and compared to the reaction in the periodontal ligament. To this end, rabbit first incisors were moved sideways with helical torsion springs for periods varying from 3–72 hours. The initial force of the springs was 50 gf. Comparison with control animals and animals wearing passive springs showed that tooth movement itself leads to trauma in the dentogingival area within only a few hours. This trauma is characterized by tears and ulcerations in the epithelium, by tears and ruptures in the fibres, by leukocytic infiltration and by the presence of extravascular erythrocytes. Between the incisors, however, a firm connective tissue septum, acting as a reinforcement to the dentogingival area, remains intact. Tissue damage significantly increases with time. After 72 hours of orthodontic force, however, the interdental papilla seems to have recovered to some extent. The histologic data of the dentogingival area in animals wearing active springs, were compared to those of the underlying periodontal ligament by multivariate analysis of variance. This analysis showed, that there are significant differences between the tissue reaction in the labial and palatal segments, and between the dentogingival and dentoalveolar areas. Furthermore, a close relationship was found between the damage to the fibres and the occurrence of extravascular erythrocytes and leukocytes. It was therefore concluded, that local tissue damage, characterized by rupture of fibres, leads to an inflammatory reaction in the gingiva and the periodontal ligament.

American Journal of Orthodontics and Dentofacial Orthopedics, 1988

This review gives a description of the biologic significance of craniofaciai sutures with respect... more This review gives a description of the biologic significance of craniofaciai 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.

Metabolic Bone Disease and Related Research, 1984

Osteoblastic and osteoclastic activity was studied in avian medullary bone in vivo. During the ac... more 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 (k 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.

ChemInform, 2010

A Novel Class of Vitamin D Analogues. Synthesis and Preliminary Biological Evaluation.-Five vitam... more A Novel Class of Vitamin D Analogues. Synthesis and Preliminary Biological Evaluation.-Five vitamin D analogues, e.g. (IV), are prepared in which the triene system and the A-ring are replaced by an aromatic ring. Generally the compounds demonstrate a high affinity towards the vitamin D receptor. The vitamin D analogues are relatively good binders.

Steroids, 1997

A synthesis and an in vitro evaluation of side chain-unsaturated analogs 3 and 4 of 24a,24b-dihom... more A synthesis and an in vitro evaluation of side chain-unsaturated analogs 3 and 4 of 24a,24b-dihomo-l,25dihydroxycholecalciferol (1) are described. Novel C23,,.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 I2 or Wittig reagent 15for the preparation of compound I and analog 4, respectively. Introduction of a 24aE double bond results in a selective, lO00-fold increase in the binding affinity of analog 4for 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.

Endocrinology, 1984

PTH bioactivity during the egg-laying cycle of the chicken has been measured by the cytochemical ... more 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.

Current Pharmaceutical Design, 2000

Chirality, 1999

A series of analogs of 1,25-dihydroxycholecalciferol was obtained with an additional chiral cente... more 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 C 23a,24-or C 22-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.

Chirality, 1999

A series of analogs of 1,25-dihydroxycholecalciferol and 25hydroxycholecalciferol were obtained w... more A series of analogs of 1,25-dihydroxycholecalciferol and 25hydroxycholecalciferol were obtained with an additional hydroxyl in the aliphatic side chain at carbon atom C-24. These analogs were synthesized by direct and diastereoselective ␣-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)-1,24,25trihydroxycholecalciferol for the calf thymus intracellular vitamin D receptor was one order of magnitude higher than that of the respective (24S)-diastereomer. Chirality