Dynamics of recovery of morphometrical variables and pQCT-derived cortical bone properties after a short-term protein restriction in maturing rats.

Severe protein restriction during the post-weaning period in the rat markedly reduces femoral bone mass and produces a number of alterations in the shaft biomechanical properties. Body weight and femur length show an immediate and complete catch-up during nutritional rehabilitation. The aim of the present investigation was to assess whether the accelerated bone growth that occurs during protein rehabilitation is accompanied by recovery of cortical bone properties. The dynamics of the recovery of both material and geometric properties were thus evaluated on the femoral diaphyses in 45-day old female rats after a 10-day period of dietary protein restriction by peripheral quantitative computed tomography (pQCT). Protein starvation led to marked reduction of both body weight and femoral length (37% and 14% at day 10, respectively) which showed a complete catch-up after 30 d of protein refeeding. Protein restriction was associated with the interruption of the natural increase in cortical area (CtCSA), volumetric cortical bone mineral content (vCtBMC) and volumetric cortical bone mineral density (vCtBMD) which were 19.7, 25.8, and 14%, respectively, in malnourished than in control rats at the end of the protein starvation period. These parameters recovered completely during protein refeeding. Treatment also reduced by 30% both rectangular (xCSMI) and polar (pCSMI) moments of inertia. Although an improvement of these architectural indicators occurred with time, an approximately 20% deficit was still present at the end of the observation period (70 d), as was the bone strength index (BSI). It is concluded that protein restriction affected the adaptation of diaphyseal design which should reduce the mechanical competence of the femoral diaphysis because of an inadequate architectural distribution of cortical bone, and that the alteration did not show complete catch-up during the studied period.

Bone growth in nonorganic nutritional dwarfing rats.

Since no data are available to characterize mandibular growth in nonorganic nutritional dwarfing (ND), the purpose of the present study was to describe the effects of a diet on mandible and femur growth in a nutritional dwarfish animal model. Male Wistar rats were divided into two groups of 10 animals each: Control (C) and Experimental (E80: diet-restricted group). C rats were fed a standard diet ad libitum. E80 rats received 80% of the amount of standard diet eaten by group C. Food intake and body weight (Wt) and length (Lt) were recorded periodically. Growth data (Wt and Lt) were expressed as a Z-score of weight-for-length (WLZ) ratio, an index of body size. Five animals of each group were selected at random at 4 and 8 weeks and sacrificed. Additionally at t = 0, 5 animals were sacrificed for baseline measurements. Mandibular growth was estimated directly on the right mandible by measuring ten dimensions. Femur growth was estimated from Wt and Lt measurements of the bone. Mandibular weight, area, length and height were negatively affected by dietary restriction during the first 4 weeks of the experimental period. Mandibular growth ceased after this point. Dimensions corresponding to the alveolar unit did not change with time. However, all other dimensions were negatively influenced but not to the same extent. Femur rather than mandibular weight was severely affected. Therefore, the negative effects of the nutritional stress that occurs after weaning would be stronger for the femur, than for the mandible. Femur length was also negatively affected by suboptimal nutrition. In summary, the results of the present study showed that mandible and femur growth respond differently to mild chronic food restriction. These observations could be explained in terms of the different critical bone growth periods and of the time at which nutritional stress was imposed.

Bone growth in nonorganic nutritional dwarfing rats.

Since no data are available to characterize mandibular growth in nonorganic nutritional dwarfing (ND), the purpose of the present study was to describe the effects of a diet on mandible and femur growth in a nutritional dwarfish animal model. Male Wistar rats were divided into two groups of 10 animals each: Control (C) and Experimental (E80: diet-restricted group). C rats were fed a standard diet ad libitum. E80 rats received 80

of the amount of standard diet eaten by group C. Food intake and body weight (Wt) and length (Lt) were recorded periodically. Growth data (Wt and Lt) were expressed as a Z-score of weight-for-length (WLZ) ratio, an index of body size. Five animals of each group were selected at random at 4 and 8 weeks and sacrificed. Additionally at t = 0, 5 animals were sacrificed for baseline measurements. Mandibular growth was estimated directly on the right mandible by measuring ten dimensions. Femur growth was estimated from Wt and Lt measurements of the bone. Mandibular weight, area, length and height were negatively affected by dietary restriction during the first 4 weeks of the experimental period. Mandibular growth ceased after this point. Dimensions corresponding to the alveolar unit did not change with time. However, all other dimensions were negatively influenced but not to the same extent. Femur rather than mandibular weight was severely affected. Therefore, the negative effects of the nutritional stress that occurs after weaning would be stronger for the femur, than for the mandible. Femur length was also negatively affected by suboptimal nutrition. In summary, the results of the present study showed that mandible and femur growth respond differently to mild chronic food restriction. These observations could be explained in terms of the different critical bone growth periods and of the time at which nutritional stress was imposed.

Bone growth in nonorganic nutritional dwarfing rats

Since no data are available to characterize mandibular growth in nonorganic nutritional dwarfing (ND), the purpose of the present study was to describe the effects of a diet on mandible and femur growth in a nutritional dwarfish animal model. Male Wistar rats were divided into two groups of 10 animals each: Control (C) and Experimental (E80: diet-restricted group). C rats were fed a standard diet ad libitum. E80 rats received 80

of the amount of standard diet eaten by group C. Food intake and body weight (Wt) and length (Lt) were recorded periodically. Growth data (Wt and Lt) were expressed as a Z-score of weight-for-length (WLZ) ratio, an index of body size. Five animals of each group were selected at random at 4 and 8 weeks and sacrificed. Additionally at t = 0, 5 animals were sacrificed for baseline measurements. Mandibular growth was estimated directly on the right mandible by measuring ten dimensions. Femur growth was estimated from Wt and Lt measurements of the bone. Mandibular weight, area, length and height were negatively affected by dietary restriction during the first 4 weeks of the experimental period. Mandibular growth ceased after this point. Dimensions corresponding to the alveolar unit did not change with time. However, all other dimensions were negatively influenced but not to the same extent. Femur rather than mandibular weight was severely affected. Therefore, the negative effects of the nutritional stress that occurs after weaning would be stronger for the femur, than for the mandible. Femur length was also negatively affected by suboptimal nutrition. In summary, the results of the present study showed that mandible and femur growth respond differently to mild chronic food restriction. These observations could be explained in terms of the different critical bone growth periods and of the time at which nutritional stress was imposed.

[Nutrition dwarfism: longitudinal analysis of anthropometric and metabolic parameters in rats]. / Enanismo por desnutricion: cronodinamia de los procesos metabolicos en ratas.

UNLABELLED: Nutritional dwarfing (ND) is the result of nonorganic causes reflective of a voluntary or unintentional reduction in food intake, inappropriate eating behavior, dissatisfaction with body weight or unhealthy approaches toward weight control. Patients with ND have reached an equilibrium between their genetic growth potential and their nutritional intake. This study was undertaken to compare on a growing rat model the metabolic alterations in terms of substrate utilization (SU), oxygen consumption (VO2) and growth rate velocity. Twenty male weanling Wistar rats were randomized to 3 groups: control (C), experimental 4 (E4) and 8 (E8). C was fed "ad libitum" with a stock diet, E4 and E8 were underfed by 80% of the requirements during four or eight weeks, respectively. During the depletion phase the following measurements were performed: 1a) body weight (Wt), 1b) length, 1c) Weight for Length ratio z-score, 2) Body composition (BC) by EM-SCAN Tobec Model 3 000, Springfield. USA, 3) VO2 by indirect calorimetry, ECO-OXYMAX. RESULTS: 1) wt for length was -0.70 +/- 0.43 for E4 (t = 4 weeks) and 1.44 +/- 0.32 for E8 (t = 8 weeks), 2% of fat mass was within the normal range, 3) VO2 was not significantly different between groups. Chronic suboptimal nutrition (80%) decreased growth velocity which was the sole manifestation of nutritional inadequacy.

Unmodified erythropoietic response to a beta adrenergic agonist in hypothyroid mice.

beta-adrenergic agonists are able to increase erythropoiesis in the polycythemic mouse model by possibly increasing erythropoietin secretion. Since a great deal of evidence indicates that the actions of thyroid hormones and catecholamines are intimately interrelated, the present study was designed to estimate the erythropoietic response to isoproterenol, a very well-known beta-adrenergic agonist, in hypothyroid mice. Adult male CF-1 mice, maintained on a standard rodent chow and water (euthyroid) or 0.1% propylthiouracil (PTU) solution (hypothyroid) ad libitum during 37 days. Plasma T4 concentration was 1.75 +/- 0.25 micrograms/ml in euthyroid and < 1.0 microgram/ml in hypothyroid mice at this time. Mice were transfused with 1.0 ml of packed homologous red cells and the erythropoietic effect of graded doses (50, 500 and 5000 micrograms/kg) were tested by the RBC-59Fe incorporation method. No statistically significant differences (unpaired t test) were found between euthyroid and hypothyroid mice. Hypothyroidism, therefore, does not affect beta-adrenergic agonist-induced erythropoietin secretion in the present experimental conditions.

Additive effects of dietary protein and energy deficiencies on mandibular growth in the weanling rat.

Dietary protein restriction adversely affects mandibular growth in the weanling rat. Protein deficiency is usually accompanied by reduced food intake which, in turn, induces energy deficiency. The present study was thus designed to dissociate the effects of dietary protein and energy deficiencies on the growth of the mandible in rapidly growing rats. Four groups of Sprague-Dawley rats aged 30 days were fed a normal diet, a low-energy diet, a low protein diet, and a low-protein and low-energy diet for 20 days. Rats were sacrificed at the end of experimental period and body weight and mandibular dimensions were recorded to evaluate body growth and mandibular growth. The growth of the mandible was affected almost in the same order of magnitude by both protein and energy restrictions. When both were applied together, mandibular growth was even more severely affected. Two way analysis of variance revealed the absence of synergism between variables, indicating that the negative effects of dietary protein and energy restrictions on mandibular growth could be considered to be additive.

Additive effects of dietary protein and energy deficiencies on mandibular growth in the weanling rat.

Dietary protein restriction adversely affects mandibular growth in the weanling rat. Protein deficiency is usually accompanied by reduced food intake which, in turn, induces energy deficiency. The present study was thus designed to dissociate the effects of dietary protein and energy deficiencies on the growth of the mandible in rapidly growing rats. Four groups of Sprague-Dawley rats aged 30 days were fed a normal diet, a low-energy diet, a low protein diet, and a low-protein and low-energy diet for 20 days. Rats were sacrificed at the end of experimental period and body weight and mandibular dimensions were recorded to evaluate body growth and mandibular growth. The growth of the mandible was affected almost in the same order of magnitude by both protein and energy restrictions. When both were applied together, mandibular growth was even more severely affected. Two way analysis of variance revealed the absence of synergism between variables, indicating that the negative effects of dietary protein and energy restrictions on mandibular growth could be considered to be additive.

Additive effects of dietary protein and energy deficiencies on mandibular growth in the weanling rat

Dietary protein restriction adversely affects mandibular growth in the weanling rat. Protein deficiency is usually accompanied by reduced food intake which, in turn, induces energy deficiency. The present study was thus designed to dissociate the effects of dietary protein and energy deficiencies on the growth of the mandible in rapidly growing rats. Four groups of Sprague-Dawley rats aged 30 days were fed a normal diet, a low-energy diet, a low protein diet, and a low-protein and low-energy diet for 20 days. Rats were sacrificed at the end of experimental period and body weight and mandibular dimensions were recorded to evaluate body growth and mandibular growth. The growth of the mandible was affected almost in the same order of magnitude by both protein and energy restrictions. When both were applied together, mandibular growth was even more severely affected. Two way analysis of variance revealed the absence of synergism between variables, indicating that the negative effects of dietary protein and energy restrictions on mandibular growth could be considered to be additive.

Impaired response of polycythemic mice to erythropoietin induced by protein starvation imposed after hormone administration.

The present study was performed to determine the stage of the erythropoietic pathway which is affected by starvation or protein deprivation and whose manifestation is a depressed response to exogenous erythropoietin (EPO). The response to recombinant human EPO was measured in post-hypoxic polycythemic mice by determination of 59Fe uptake into red cells, spleen and femur and/or erythroid colony forming units (CFU-E) and erythroid precursor cell concentrations in femoral marrow. Experimental mice were either starved or fed one of seven different diets whose protein (casein) content ranged from 0 to 20%. All diets were isocaloric. The response of mice maintained on the standard diet (Purina Lab chow) was taken as the normal one. Starvation during the 48-hour period immediately before EPO injection had no effect on the response to the hormone. Starvation, and protein deprivation to a lesser extent, during the 48-hour period following EPO, on the other hand, significantly reduced the response. There was a progressive increase in the response as the casein content of the diet was increased. A normal response was observed when dietary casein concentration was 10%. These findings indicate that nutritional deprivation or dietary protein alterations during the period immediately following EPO injection in polycythemic mice can have detrimental effects on the erythroid response in a model in which nutritional deprivation was relatively short and acute. They also indicate that the subnormal response is not due to a decreased size of the erythroid progenitor pool available for differentiation but to deficient rates of differentiation of erythropoietic units.