Biomedical subjects

Christos Katsaros

Publications and source records attributed to Christos Katsaros.

10 recordsLinked to original sources

PubMed2006

Cytoskeleton and morphogenesis in brown algae.

BACKGROUND: Morphogenesis on a cellular level includes processes in which cytoskeleton and cell wall expansion are strongly involved. In brown algal zygotes, microtubules (MTs) and actin filaments (AFs) participate in polarity axis fixation, cell division and tip growth. Brown algal vegetative cells lack a cortical MT cytoskeleton, and are characterized by centriole-bearing centrosomes, which function as microtubule organizing centres. SCOPE: Extensive electron microscope and immunofluorescence studies of MT organization in different types of brown algal cells have shown that MTs constitute a major cytoskeletal component, indispensable for cell morphogenesis. Apart from participating in mitosis and cytokinesis, they are also involved in the expression and maintenance of polarity of particular cell types. Disruption of MTs after Nocodazole treatment inhibits cell growth, causing bulging and/or bending of apical cells, thickening of the tip cell wall, and affecting the nuclear positioning. Staining of F-actin using Rhodamine-Phalloidin, revealed a rich network consisting of perinuclear, endoplasmic and cortical AFs. AFs participate in mitosis by the organization of an F-actin spindle and in cytokinesis by an F-actin disc. They are also involved in the maintenance of polarity of apical cells, as well as in lateral branch initiation. The cortical system of AFs was found related to the orientation of cellulose microfibrils (MFs), and therefore to cell wall morphogenesis. This is expressed by the coincidence in the orientation between cortical AFs and the depositing MFs. Treatment with cytochalasin B inhibits mitosis and cytokinesis, as well as tip growth of apical cells, and causes abnormal deposition of MFs. CONCLUSIONS: Both the cytoskeletal elements studied so far, i.e. MTs and AFs are implicated in brown algal cell morphogenesis, expressed in their relationship with cell wall morphogenesis, polarization, spindle organization and cytokinetic mechanism. The novelty is the role of AFs and their possible co-operation with MTs.

Actin Cytoskeleton↗

PubMed2006

Functional influence on sutural bone apposition in the growing rat.

INTRODUCTION: The aim of this study was to quantify the influence of reduced masticatory muscle function on sutural bone apposition in the growing rat. METHODS: Twenty-six growing male albino rats were randomly divided into 2 equal groups; 1 (hard-diet group) received the ordinary diet of hard pellets, and the other (soft-diet group) received the powdered form of the ordinary diet mixed with water. The experimental period started when the rats were 4 weeks old and lasted 42 days. At days 0, 14, and 28, calcein was injected into all animals. At the end of the experiment, the animals were killed, and the heads were taken for preparation of undecalcified frontal sections, 120 microm thick. Three representative homologous sections for each animal in both groups were selected and studied under a fluorescence microscope. The level of bone apposition at the time of calcein injection was marked with separate fluorescing lines. Because the lines from the first injection could not be seen in all areas, bone apposition in the internasal, naso-premaxillary, and inter-premaxillary sutures was quantified from day 14 to the end of the experimental period, by using an image analysis software. RESULTS: In both groups, greater bone apposition was found between days 14 and 28 than between days 28 and 42 of the experimental period. Less bone apposition was found in the soft-diet group than in the hard-diet group in all sutures studied. CONCLUSIONS: The findings suggest that bone apposition in the studied facial sutures in the anterior facial skeleton of the growing rat is significantly affected by reduced masticatory function.

Analysis of Variance↗

PubMed2006

Dental maturation in short and long facial types. Is there a difference?

OBJECTIVE: The purpose of this investigation was to study the relationship between vertical skeletal growth pattern and dental maturation in children with long or short anterior facial height. MATERIALS AND METHODS: The sample consisted of the records of 312 Dutch children (153 boys and 159 girls, aged 9-12.9 years, with a mean chronological age of 11.3 years). The subjects were selected according to their lower anterior facial height as a percentage of the total facial height. Two groups, one with long and the other with short anterior facial height, were formed for further comparison. Dental age, according to Demirjian's dental maturity score, was determined for each subject. The power of the study was 79% (2-sided test) and 87% (1-sided test). RESULTS: There was no statistically significant difference in dental age score between the two extreme groups. The subjects with short anterior facial height demonstrated a slight tendency toward more advanced dental age. CONCLUSIONS: The difference in dental age between long and short facial types is not big enough to be clinically relevant.

Age Determination by Skeleton↗

PubMed2006

Dental age in children with a complete unilateral cleft lip and palate.

OBJECTIVE: To assess dental age in children with a complete unilateral cleft lip and palate and to compare this with a noncleft control group. DESIGN: Two-group, mixed-longitudinal cohort study. SETTING: Cleft group from an academic center for cleft lip and palate treatment. Noncleft control group from the same population. PATIENTS: Participants included 70 Caucasian children with a full complement of teeth and a complete unilateral cleft lip and palate (45 boys and 25 girls) from the Cleft Palate Craniofacial Center at the Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands. The control group (90 boys and 91 girls) was taken from the Nijmegen Growth Study. MAIN OUTCOME MEASURE: Dental age was assessed on orthopantomograms. In the unilateral cleft lip and palate group, linear interpolation in individual age curves was applied to obtain the dental age at 5, 9.5, and 14 years of age. For these ages, a comparison was made with the noncleft control group. RESULTS: Boys and girls with a unilateral cleft lip and palate showed a significant delay in dental age, as compared with their noncleft peers at all three ages. This delay was more pronounced in boys than in girls. The gender effect was significant at chronological ages 5 and 14 years. CONCLUSIONS: Children with a complete unilateral cleft lip and palate have a delay in dental age, compared with noncleft children.

Adolescent↗

PubMed2005

Treatment outcome in unilateral cleft lip and palate evaluated with the GOSLON yardstick: a meta-analysis of 1236 patients.

BACKGROUND: The goal of this study was to assess determinants for treatment outcome in unilateral cleft lip and palate, evaluated according to the Great Ormond Street London and Oslo (GOSLON) Yardstick and 5-year-index ratings by means of a meta-analysis. METHODS: Multiple databases were searched for publications in which patient groups were evaluated by GOSLON ranking or the GOSLON-like 5-year index. From the 15 selected publications, the following background variables could be extracted and were evaluated as determinants for treatment outcome in unilateral cleft lip and palate: year of birth, average age of the patient at the time of GOSLON classification, racial background, presence of Simonart's band, infant orthopedics, palatal closure before the age of 3 versus palatal closure at a later age, bone graft, and number of surgeons. RESULTS: The total number of patients included in the meta-analysis was 1236. Patients whose soft and hard palate were closed before the age of 3 presented significantly poorer (p = 0.003) GOSLON scores (mean score, 2.9; SD 0.4) than patients whose palate was closed at a later age (mean GOSLON score, 2.3; SD 0.2). CONCLUSIONS: Delayed palatal closure generally results in better dental arch relationships than early palatal closure. Well-designed, randomized clinical trials are required for further investigation of the optimal timing for palatal closure.

Age Factors↗

PubMed2005

Treatment outcome after two-stage palatal closure in unilateral cleft lip and palate: a comparison with Eurocleft.

OBJECTIVE: To evaluate dental arch relationships of patients with unilateral cleft lip and palate (UCLP) treated with a two-stage palatal closure and to compare them with the six centers from the Eurocleft study that used various treatment protocols. DESIGN: Repeated-measures study. SETTING: Cleft Palate Craniofacial Unit of Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands. PATIENTS: Records of 9-year-old children with complete unilateral cleft lip and palate (n = 43) were included. INTERVENTIONS: The dental arch relationships of these patients were assessed by applying the Goslon Yardstick and subsequently compared with the Goslon outcome of the six-center Eurocleft study. MEAN OUTCOME MEASURES: Statistics of intra- and interexaminer agreement. RESULTS: For the Nijmegen UCLP group, 9% of dental arch relationships had a Goslon score of 1, 52% had a score of 2, 30% has a score of 3, 9% had a score of 4, and none had a score of 5. The mean Nijmegen Goslon score showed no significant differences with Eurocleft centers A, B, and E, which achieved the best treatment results, but did significantly differ from Goslon outcomes of Eurocleft centers D (p < .001), C, and F (p < .01), which had relatively poor treatment outcome. CONCLUSIONS: Treatment outcome of the patients in the Nijmegen UCLP group treated with two-stage palatal closure was comparable with the results of the Eurocleft centers with the best outcome. Treatment protocol could not explain differences in the quality of treatment results.

Age Factors↗

PubMed2004

Photographs of study casts: an alternative medium for rating dental arch relationships in unilateral cleft lip and palate.

OBJECTIVE: To investigate the reliability of using photographs of study casts as an alternative to casts for rating dental arch relationships. DESIGN: Repeated-measures study. SETTING: Cleft Palate Center of the University Medical Center Nijmegen, Nijmegen, The Netherlands. PATIENTS: Records of children with complete unilateral cleft lip and palate (UCLP) (n = 49) at the age of 9 years were included. MEAN OUTCOME MEASURE(S): Statistics of intra- and interexaminer agreement. RESULTS: No significant differences were found between the rating of dental casts and photographs of dental casts, using the Goslon Yardstick. CONCLUSIONS: Photographs of dental casts provide a consistent, reproducible method for rating dental arch relationships in patients with UCLP at the age of 9 years and provide a reliable alternative to the application of the Goslon Yardstick on dental casts.

Child↗

PubMed2003

Masseter muscle thickness and maxillary dental arch width.

The purpose of the present investigation was to study the relationship between the ultrasonographic thickness of the masseter muscle and the width of the maxillary dental arch. The sample comprised 60 consecutive orthodontic patients (37 females, 23 males), 7-18 years of age with a Class I relationship and minor malocclusion. The thickness of the masseter muscle was measured ultrasonographically. Recordings were performed bilaterally with the muscles both in relaxation and under contraction. Maxillary intermolar width was measured with an electronic calliper as the distance between the palatal surfaces of the first permanent molars. Intermolar width showed no association with age and gender. However, masseter muscle thickness showed a direct, significant (P < 0.0001) association with these two factors together, i.e. the masseter muscle was thicker in older individuals and in males. In the female group, maxillary intermolar width showed a direct, significant association with masseter thickness both during contraction (P < 0.006) and relaxation (P < 0.013), i.e. females with thicker masseter muscles had a wider maxillary dental arch. In the male group, however, no significant relationship was found between maxillary intermolar width and masseter thickness. The findings of this study indicate that the functional capacity of the masticatory muscles may be considered as one of the factors influencing the width of the maxillary dental arch.

Adolescent↗

PubMed2003

Segment distraction to reduce a wide alveolar cleft before alveolar bone grafting.

OBJECTIVE: To demonstrate a method for reduction of wide alveolar clefts prior to bone grafting. This method aims to facilitate bone grafting and achieve adequate soft tissue coverage of the graft with attached gingiva. CASE REPORT: Treatment of a patient with bilateral cleft lip and palate with a severe alveolar defect on the left side is illustrated. Distraction osteogenesis was used to mesialize the left segment so that the alveolar cleft was reduced to a minimum. After a 10-week retention period, bone grafting of the reduced alveolar defect was successfully performed. After consolidation of the bone graft, the alveolar cleft was found to have an osseous closure with adequate soft tissue coverage. CONCLUSION: In patients with a wide alveolar cleft, soft tissue coverage with keratinized mucosa can be more readily assured by reducing the alveolar cleft by callus distraction to mesialize the lateral segment prior to bone grafting.

Alveolar Process↗

PubMed2002

Influence of masticatory muscle function on transverse skull dimensions in the growing rat.

AIM: The aim of this study was to elucidate the influence of reduced masticatory muscle function on the transversal dimensions of the premaxilla, maxilla (including the dental arch) and the calvaria in the growing rat. MATERIAL AND METHODS: 38 growing male albino rats were used. 14 animals were killed at the beginning of the experiment to provide baseline values (Young Group). The remaining animals were randomly divided into two equal groups; one received the ordinary diet in hard pellet form (Hard Diet Group), and the other a soft diet (Soft Diet Group). The experimental period started when the rats were 28 days old and had a duration of 28 days. 3D measurements of the dentofacial skeleton were performed on dry skulls with a Reflex microscope. RESULTS: No inter-group differences were found in mean body weight and overall length of the cranium. The dental arch was found to be narrower in the third molar region in the Soft Diet Group, possibly due to less growth in the midpalatal suture and/or to reduced occlusal loading. This may be due to the first and second molars having been in occlusion at the beginning of the experimental period, while the third molars were not. Furthermore, the premaxilla and the frontal bones at the most lateral part of the temporal crest were narrower in the Soft Diet Group, these regions being areas of masticatory muscle attachment.

Animals↗