Participación de MT1-MMP en la remodelación del ligamento periodontal durante la movilización dentaria / Role of MT1-MMP in the remodeling of the periodontal ligament during tooth movement

La movilización dentaria involucra una serie de cambios en los tejidos de soporte caracterizados por la activa remodelación de estos. La MT1-MMP o MMP-14 es una potente enzima proteolítica capaz de degradar colágeno tipo I, la principal molécula estructural del ligamento periodontal. La migración dentaria requiere de la degradación controlada del colágeno constituyente del ligamento periodontal. Sin embargo, no existen evidencias de la participación de MT1-MMP en la remodelación del tejido periodontal durante este proceso. En el presente estudio hemos analizado la expresión de MT1 -MMP y del marcador de actividad osteoclástica Fosfatasa Acida Tartrato Resistente (TRAP) en un modelo de migración dentaria en ratas. La migración dentaria fue activada mediante la inserción de una banda separadora entre los incisivos superiores. La expresión y distribución de TRAP y MT1-MMP fue evaluada a través de citoquímica e inmunohistoquímica a los días 1, 3, 5 y 7. La producción de TRAP fue identificada principalmente en osteoclastos ubicados en la zona de compresión del ligamento periodontal. La producción de MT1-MMP fue observada en fibroblastos de la zona de compresión del ligamento periodontal y osteoclastos ubicados en esta misma región. Nuestros resultados permiten proponer que tanto MT1 -MMP como TRAP participan en la remodelación de los tejidos de soporte periodontal durante la migración dentaria.

Tooth movement involves a series of changes of the supporting periodontal tissues characterized by the active connective tissue remodeling. MT1-MMP or MMP-14 belongs to the family of matrix metalloproteinases that are able to degrade type I collagen, the main molecule involved in periodontal attachment. Tooth migration requires the controlled degradation of periodontal ligament collagen fibers. However, evidences linking MT1 -MMP expression with periodontal tissue remodeling are lacking. In the present study, we have evaluated the expression of MT1-MMPand of the osteoclast marker Tartrate Resistant Acid Phosphatase (TRAP) in a model of tooth migration in rats. Tooth migration was induced after the insertion of a rubber band between the upper incisors. The distribution of TRAP and MT1 -MMP was evaluated by means of cytochemistry and immunohistochemistry respectively at days 1, 3, 5 and 7. TRAP production was identified in osteoclasts at the area of compression of the periodontal ligament. MT1-MMP distribution was observed in fibroblastsatthe compressed area of the periodontal ligament and also in osteoclasts of the same region. Our findings allow us to propose that MT1-MMP and TRAP take part of the tissue remodeling events observed during tooth movement.

Noninvasive determination of the anaerobic threshold in canoeing, cross-country skiing, cycling, roller, and ice-skating, rowing, and walking.

The relationship between velocity (V) and heart rate (HR) was determined in four canoeists, 42 cross-country skiers, 73 cyclists, nine ice-skaters, 10 roller-skaters, 32 rowers, and 20 walkers. The athletes were asked to increase their work intensity progressively, from low to submaximal velocities; HRs were determined by ECG in roller-, ice-skating, and walking, or read on a cardiofrequency meter in canoeing, cross-country skiing, cycling, and rowing. In all the athletes examined the linearity of the V-HR relationship was maintained up to a submaximal speed (deflection velocity, Vd), beyond which the increase in work intensity exceeded the increase in HR. Vd and anaerobic threshold (AT), determined through blood lactate measurements, were coincident in 19 athletes (6 cross-country skiers, 3 cyclists, 2 roller-skaters, 3 rowers, and 5 walkers). Vd was correlated with the average speeds maintained in walking (20 km, n = 13, r = 0.88), cross-country skiing (15 km, n = 20, r = 0.80; 30 km, n = 8, r = 0.82; 12 km, n = 7, r = 0.86; 11 km, n = 7, r = 0.86) and cycling (1,000 m flying-start, n = 68, r = 0.83), thus showing that AT is a limiting factor in these aerobic events.

[Hematological variables in marathon and ultramarathon runners]. / Variabili ematologiche in maratoneti ed ultramaratoneti.

The haemoglobin concentration of runners has been reported to be often below normal (1). In the present investigation the haemoglobin and iron concentrations and the haematocrit have been determined in 45 marathon runners examined before and after the 1982 Italian Marathon Championship and in 79 runners examined before and after the 1982 Firenze-Faenza race (107 km). The results obtained suggest that the training programs followed by the marathon runners (up to 260 km per week in the months preceding the race) are accompanied by a significant decrease of the haemoglobin and iron levels and of the haematocrit. Similar results have been observed in the participants to the Firenze-Faenza race. Nevertheless in these ultramarathoners the decrease of the haemoglobin and iron concentration and of the haematocrit are less marked, possibly because their training programs are less intense than those of the marathon runners. The findings obtained are in favour of the hypothesis that the degree of "sport anaemia" might be related to the amount of training of the athletes.

[Endurance of 6 marathon runners before and after a "dissociated diet"]. / Valutazione della resistenza di 6 maratoneti prima e dopo "dieta dissociata".

The effect of a carbohydrate loading diet on the endurance of six male marathon runners have been examined. Endurance improved in three runners, remained unchanged in two, and worsened in one. Due to the possibility of negative effects on the performance capability, a runner should experiment his personal reactions to the carbohydrate loading diet before using it regularly for long distance competitions.

Determination of the anaerobic threshold by a noninvasive field test in runners.

The relationship between running speed (RS) and heart rate (HR) was determined in 210 runners. On a 400-m track the athletes ran continuously from an initial velocity of 12-14 km/h to submaximal velocities varying according to the athlete's capability. The HRs were determined through ECG. In all athletes examined, a deflection from the expected linearity of the RS-HR relationship was observed at submaximal RS. The test-retest correlation for the velocities at which this deflection from linearity occurred (Vd) determined in 26 athletes was 0.99. The velocity at the anaerobic threshold (AT), established by means of blood lactate measurements, and Vd were coincident in 10 runners. The correlation between Vd and average running speed (mean RS) in competition was 0.93 in the 5,000 m (mean Vd = 19.13 +/- 1.08 km/h; mean RS = 20.25 +/- 1.15 km/h), 0.95 in the marathon (mean Vd = 18.85 +/- 1.15 km/h; mean RS = 17.40 +/- 1.14 km/h), and 0.99 in the 1-h race (mean Vd = 18.70 +/- 0.98 km/h; mean RS = 18.65 +/- 0.92 km/h), thus showing that AT is critical in determining the running pace in aerobic competitive events.

[Determination of the anaerobic threshold by a noninvasive field in man]. / Un test da campo per la determinazione della soglia anaerobica nell'uomo.

The relationship between running velocity and heart rate has been determined in 320 runners. A deflection from the expected linearity of this relationship has been observed at sub-maximal running speeds. Deflection velocity and anaerobic threshold (established through blood lactate determination) were coincident in 10 runners, thus showing that the increase in running speed exceeding the augmentation in heart frequency above Vd depends on anaerobic ATP production.