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Biomedical subjects

O Rönning

Publications and source records attributed to O Rönning.

At least 19 recordsLinked to original sources
PubMed1999

Effect of methotrexate alone and in combination with vincristine on craniofacial morphology in growing rats.

Craniofacial growth in young Long-Evans/Turku strain rats was studied following administration at different intervals of the antineoplastic agent methotrexate (MTX) and of a combination of two agents, MTX and vincristine (VCR). The 10-day-old rats tolerated only 1 subcutaneous injection of 0.75 mg/kg MTX, while single and repeated doses of 1.0 mg/kg MTX, or of the combination of MTX (1.0 mg/kg) and VCR (0.05 mg/kg), could be used for the 30-day-old rats. The rats were killed 20 days after the start of the experiment, i.e. at 30 or 50 days of age, respectively; their weights were recorded and a total of 12 craniofacial dimensions were measured. Owing to the relatively few significant sex differences, the dimensions recorded for the females and males were pooled. Administration of MTX alone or combined with VCR caused disturbed craniofacial growth, which was already evident following 1 single injection of MTX in the younger rats (10 to 30 days) and after repeated injections (every third day) of MTX alone or combined with VCR in the older rats (30 to 50 days). The body weights of all the medicated rats were initially retarded and catch-up growth, i.e. a return to control body weight levels, occurred by the end of the experiment only in the rats that received a single injection of MTX, but not after repeated injections. We conclude that the antineoplastic agent MTX alone or in combination with VCR administered at short intervals with pharmacologically adjusted doses has a short-term effect on the craniofacial skeleton of growing rats.

Age Factors↗
PubMed1997

Abnormal craniofacial growth and early mandibular osteoarthritis in mice harbouring a mutant type II collagen transgene.

Skull morphology and histology in the heterozygous offspring of a transgenic founder mouse Del1, harbouring 6 copies of deletion mutation in Col2a1 gene, were compared with those in normal siblings. On visual observation and roentgenocephalometric examination the heads of heterozygous Del1 mice were smaller than normal. Histologically the sizes of cartilaginous structures of the cranial base were reduced. Severe defects were seen in the temporomandibular joint as progressive osteoarthritic lesions. These observations elucidate the relationship between the genotype and phenotype and demonstrate that heterozygous Del1 mice are a useful model for studies on a genetic disturbance where 'clinical' manifestations are not evident until adult age.

Animals↗
PubMed1997

Tissue-separating capacity of growth cartilages.

The tissue-separating capacity of chondral structures has been debated for more than 30 years, and one aspect that has particularly been questioned is whether the secondary cartilage of the mandibular condyle is comparable to primary growth cartilage, e.g. the epiphyseal growth plate. The present report summarizes information gained by using a specific interosseal transplantation method. These findings lead to the conclusion that all the structures examined, i.e. the proximal epiphyseal cartilage of the tibia, the cartilage of the costochondral junction of the ribs, the basicranial synchondroses, the medial cartilage of the clavicle and the mandibular condyle, have the capacity to separate adjoining skeletal structures. The changes induced by the transplanted structures in the recipient area vary, however, suggesting a hierarchial arrangement of cartilages with regard to their tissue-separating capacity. It is suggested that the tissue-separating capacity is a basic phenomenon in the function of growth, not only of primary growth cartilages, but of secondary cartilages as well.

Animals↗
PubMed1997

Effect of freezing damage of the periosteum on the growth of the mandibular condylar process in the rat.

The regulatory effect of the periosteum on the growth of the mandibular condylar process has previously been investigated by relieving the periosteal tension, e.g. by dividing the periosteum, but no unanimous conclusion has been reached. In the present investigation, a different experimental design was applied in that the growth of the condylar process was observed following a provoked periosteal damage. Using 15-day-old rats, the mandibular ramus on the right side was exposed, and the periosteum subjacent to the condylar cartilage was frozen by a cryotechnique. Controls were treated similarly, with the exception of the freezing. The height of the ramus and the length of the mandibular corpus were measured on separated dry mandibular halves 15 or 30 days postoperatively. The measurements showed that the mandibular halves on which the periosteum had been frozen were significantly smaller than the contralateral ones. A tendency in the same direction was also found in the sham-operated animals. It can be concluded that the presumably increased restriction following damage to the periosteum, and evidently also scarring resulting from the operation, has an inhibitory effect on the growth of the condylar process. However, it is still open to discussion whether the reduced growth is transmitted by mechanical means according to the periosteal-tension hypothesis and/or by here unspecified mitogenic factors.

Animals↗
PubMed1996

Lesions of the mandibular condyle in juvenile chronic arthritis.

A total of 371 serial dental panoramic radiographs from 71 children with juvenile chronic arthritis (JCA) were examined to determine the presence and extent of radiographically detectable condylar abnormalities. The series included 12 children with so called 'bird face' deformity and 55 in whom facial growth was judged to be normal. By the age of 15 years, 27 patients (38 per cent), showed lesions of the TMJ, of which 14 (55 per cent) were bilateral. Of those cases with unilateral destruction, the left condyle was affected nine times more frequently than the right. All of the children with 'bird face' deformity had condylar abnormality, but these facial characteristics should not be considered pathognomonic of juvenile chronic arthritis. Moderate to severe condylar abnormality was detectable in 10.9 per cent of children with normal facial growth, and where condylar destruction is present it can often be established as early as 8 years. Systemic corticosteroids appear to have little or no effect on the condyle or mandibular growth.

Adolescent↗
PubMed1995

Reactions of the mandible to experimentally induced asymmetrical growth of the maxilla in the rat.

The purpose of this investigation was to examine the interrelation in growth and morphogenesis between the maxilla and the mandible. Asymmetrical growth was induced in the maxilla of 10-day-old LE/T rats by means of unilateral artificial synostosis of the frontonasal and frontopremaxillary sutures. Untreated rats were used as controls. Biometric and microscopic observations were made at the ages of 30, 50, and 100 days. The arrest of sutural growth was followed by reduced sagittal growth of the maxilla, significantly more so on the treated side. Its anterior part became bent towards the treated side and rotated around the sagittal axis. In response to the primary alteration in maxillary shape, the mandible adapted by developing a secondary asymmetry in that it was shorter on the treated side than on the contralateral side throughout the experiment and shorter on the untreated side than in the untreated controls at 30 days. When the distances were adjusted for body weight, the mandibular length on the untreated side appeared to be virtually unaffected by the experimental procedure or even exceeded the control value at 50 days. The mandibular ramus was higher on the treated side than on the contralateral side at 30 days, and became bilaterally higher than in the untreated controls with increasing age. The results imply that the growth in length of the mandible follows that of the maxilla to some extent and are indicative of a restraining effect of the shortened maxilla on mandibular growth. The existence of a mechanism responsible for keeping the height of the ramus the same on both sides is suggested.

Aging↗
PubMed1995

Basicranial synchondroses and the mandibular condyle in craniofacial growth.

Basicranial synchondroses are remnants of the fetal chondrocranium and thus represent primary cartilage, whereas the chondral part of the mandibular condyle, for example, develops unattached to the chondrocranium, as secondary cartilage. The two cartilage groups show differences in structure and cell proliferation pattern, and yet both are endowed with tissue-separating qualities.

Animals↗
PubMed1994

Juvenile chronic arthritis: a cephalometric analysis of the facial skeleton.

A retrospective cross-sectional cephalometric investigation was undertaken to examine the facial form of a group of Finnish children with juvenile chronic arthritis (JCA). Following digitization, the radiographs were divided into three age groups, and according to whether or not 'bird-face' deformity was present. From a total of 67 cases (39 females and 28 males) 19 per cent were judged to be 'affected'. Analyses were carried out and the groups compared using t-tests. The mandible was found to be smaller both in ramal height and body length in the affected sample, with reduction in posterior face height being only partly compensated by increase in bony apposition at the angle producing antegonial notching. There was posterior rotation of the mandible with a reduction in angles S-N-B and S-N-Pog, and an increase in the gonial angle, the angle between the mandibular plane and S-N, maxillary, and occlusal planes. The changes in the maxilla were less marked. Although S-N-A was reduced in all three age groups, it was not significantly so. Maxillary length (ANS-PNS) was significantly smaller in the two younger age groups. In the vertical plane maxillary dimensions were reduced in the two younger age groups. A highly significant increase in the occlusal to maxillary planes angle was observed in all groups. There was, however, no difference in S-N to maxillary planes angle, indicating a more steeply inclined occlusal plane due to subnormally erupted maxillary molars. Although the inter-incisal angle was reduced there was no significant difference in the incisor inclinations in relation to the jaws and despite the posterior rotation of the mandible there was no significant increase in size of overjet or in the frequency of anterior open bite.

Adolescent↗
PubMed1993

Mandibular condyle lesions related to age at onset and subtypes of juvenile rheumatoid arthritis in 15-year-old children.

The severity of lesions in the temporomandibular joint (TMJ) area and their association with age at onset, the various forms of juvenile rheumatoid arthritis (JRA), and certain serologic tests for rheumatoid factor (RF), antinuclear antibodies (ANA), and human leukocyte antigen (HLA)-B27 were determined in 15-yr-old children. The series comprised 121 JRA children, 78 girls and 43 boys, in whom an analysis had recently been made of the relation of TMJ lesions to jaw movement and occlusal status. The mean age at onset was 7.3 yr, the girls contracting JRA earlier than the boys. Also, the girls with lesions in the TMJ area were significantly younger than those with no lesions. TMJ abnormalities were found in 50% of cases with a pauciarticular or systemic onset, but in 72% of those representing the polyarticular subtype. Flattened condyles and grave lesions were equally represented in all subgroups and in both sexes. A crossover from onset type to present diagnosis was found in 30% of the cases, mostly from pauciarticular to polyarthritis, which also increased the risk of TMJ lesions from 50 to 60%. RF, ANA, or HLA-B27 alone did not seem to be associated with a risk of TMJ abnormalities. Maximal opening capacity is more restricted in patients with early onset or a polyarticular mode of JRA. Since the TMJ is affected in more than half of JRA children, regular measurements of maximal movements of the mandible or roentgenologic examinations of the TMJ are essential for their optimal treatment.

Adolescent↗
PubMed1993

Growth of costochondral fragments transplanted from mature to young isogeneic rats.

Experiments were carried out to determine whether growth of costochondral grafts is associated with age-related humoral factors. Rib fragments containing either short (without germinative zone) or long (with proliferative and germinative zones) cartilaginous ends were excised from adult rats, and the sections transplanted across the interparietal suture in 10-day-old isogeneic rats. The animals with short cartilage transplants were killed 15 or 25 days later; those with long cartilage transplants 25 days postoperatively. Measurements on dry skulls with short transplants showed neurocranial width to be greater in the experimental rats than in the unoperated controls at 25 days, whereas 10 days later the difference was no longer significant. By the latter time, however, the neurocranium was significantly wider in the long cartilage group than in the other groups. It is suggested that the declining growth potential of the costal cartilages from the adult rats was reactivated when transplanted to younger animals, i.e., the growth of costochondral transplants is related to humoral factors.

Age Factors↗
PubMed1992

Craniofacial growth in shunt-treated hydrocephalics: a four-year roentgenocephalometric follow-up study.

The craniofacial growth of 24 shunt-treated hydrocephalics aged 5-15 years was evaluated over a 4-year period, by comparing changes in linear and angular cephalometric variables with those of an age- and sex-matched control group. The main findings were increased calvarial thickness, increased cranial base flexure, superior displacement of the sella, and a tendency for the gonial angle to remain more obtuse in the shunt-treated patients. As craniofacial growth in the latter differed only slightly from that observed in the controls, the deviations in facial morphology observed in a previous cross-sectional study of shunt-treated hydrocephalics can be taken to represent a long-term effect of the shunt treatment.

Adolescent↗
PubMed1992

Weaning and the histology of the mandibular condyle in the rat.

Eighty-eight Long Evans/Turku rats were used in the study. The effect of the articulatory function on the mandibular condyle was observed histologically during normal growth, when the rat is changing its diet from milk to whole pellets as a part of weaning. Six animals each were killed at the age of 10, 15, 20, 25, 30, 35, 40 and 50 days for histological tissue processing. For further information, 30 animals were fed a soft diet (6 animals each were killed at the age of 25, 30, 35, 40 and 50 days), and 10 animals were fed hardened pellets (2 animals each were killed at the ages of 25, 30, 35, 40 and 50 days). An even and regular transition from mesenchymal cells via immature chondroblasts into mature chondroblasts and hypertrophied chondrocytes was found at 10, 15 and 20 days during normal growth and also at 25, 30, 35, 40 and 50 days when animals were fed a soft diet. This maturing process appeared to be disturbed at the age of 25, 30, 35 and 40 days in the superior aspect of the condyle in animals fed ordinary pellets. The density of the mesenchymal cell layer was decreased, and the amount of intercellular matrix seemed to be evaluated in mesenchymal and intermediate cell layers. These features were later manifest deeper in the cartilage as acellular regions and as cell clusters. The changes were similar but more severe when the animals were fed hardened pellets.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Growth potential of the rat mandibular condyle as an isogeneic transplant traversing the interparietal suture.

The mandibular condyle of 5-, 10- or 20-day inbred male rats was transplanted across the interparietal suture of male litter-mates and the transverse dimension of the neurocranium was measured from dry skulls at 25 or 35 days. The width of the neurocranium had increased significantly from days 5 or 10 to 25 in the rats with the transplants, whereas the difference from controls was small or non-existent by 35 days. Histological examination showed that the cartilaginous zone was reduced in the transplants at 25 days but that there were still layers of chondrocytes at 35 days. It is suggested that the rat mandibular condyle is endowed with a tissue-separating, interstitial growth potential that, to some extent, is unrelated to mobility, and essentially effected by chondrocyte hypertrophy.

Animals↗
PubMed1991

Growth potential of the rat clavicle.

An experiment was performed to determine whether the clavicle, which is capped with secondary cartilage at both ends, is endowed with a tissue-separating quality or is only adaptive to forces exerted by the surrounding structures. The medial end of the clavicle from 10-day-old male rats was transplanted across the interparietal suture into an opening in the adjoining parietal bones corresponding to the outline of the transplant. The transverse dimensions of the neurocranium when measured at 25 and 35 days of age were greater in the animals with transplants than in the untreated controls. Histologic examination showed that although the cartilaginous component of the transplants was reduced, the zonal arrangements was comparable to that in situ. It was concluded that the medial end of the clavicle has a potential for separating skeletal components and that preservation of the basic structure is dependent on mechanical resistance.

Animals↗
PubMed1991

Interrelationship between size and tissue-separating potential of costochondral transplants.

The aim was to determine whether the reportedly unpredictable outcome of the use of costochondral grafts in reconstructive surgery is related to variation in growth potential between the transplanted cartilages. A rib fragment including the costochondral junction was transplanted across the interparietal suture in 10-day-old rats. The transplants contained either a short, intermediate, or long cartilaginous end and a constant length of bone. The animals were killed 25 days later and the width of the neurocranium was measured from dry skulls. The neurocranium was wider the longer the cartilaginous end of the transplant. It is concluded that costochondral transplants have an intrinsic potential for separating skeletal components and that this capacity is closely related to the amount of cartilage in the transplant.

Animals↗
PubMed1991

Cartilage, function and craniofacial morphogenesis.

While primary cartilage of the craniofacial complex is a derivative of the chondroskeleton, secondary cartilage develops in close association with membrane bone. Mobile function, motility, is not always a prerequisite for the genesis of secondary cartilage but seems necessary for its maintenance as also, evidently, is mechanical load. Both primary and secondary cartilage have active morphogenetic potentials. For the primary cartilage this potential is essentially instrinsic, as has been demonstrated with transgenic mice, for instance. Consequently, primary cartilage is less adaptive to external influences than secondary cartilage. Analysis of the factors controlling the growth of the cartilaginous structures renders their utilization in reconstructive surgery more predictable.

Animals↗