Estimación del intervalo de referencia de calcio, fósforo y fosfatasa alcalina séricos en población pediátrica utilizando una base de datos por el método de Hoffmann modificado / Determination of the reference interval of serum calcium, phosphorus, and alkaline phosphatase in the pediatric population using a data base and the modified Hoffman method

Las concentraciones de calcio (Ca), fósforo (P) y fosfatasa alcalina sérica (FAL) son extensamente evaluados en pediatría. La aplicación del procedimiento recomendado por la International Federation of Clinical Chemistry (IFCC) para evaluar FAL en el equipo Cobas 501 de Roche, requirió de una reevaluación del Intervalo de referencia (IR) en nuestra población pediátrica. El método indirecto de Hoffmann con la modificaciones propuestas por Katayev et al. provee un mecanismo para estimar IR en poblaciones de difícil estudio como la pediátrica. A partir de trabajar con nuestra base de datos nos propusimos fijar IR para Ca., P, y FAL discriminados por edad y sexo (en el caso de la FAL) en nuestra población pediátrica. Se utilizaron los resultados de un año de la base de datos del hospital de sujetos entre 0 y 18 años El total de los sujetos analizados fue de 13.906 pacientes para Calcio 14.790 para fósforo y 6.333 para FAL. En FAL encontramos dimorfismo sexual en los grupos de 7 a 9, 10 a 12, 13 a 15 y 16 a 18 años con una diferencia significativa (p<0,0001). Los IR fueron calculados con los procedimientos recomendados por edad y género, los analitos Ca y P no presentaron diferencias por sexo y las diferencias por edad no fueron significativas aunque sí resultaron útiles para fijar los rangos frente a la FAL. El método de Hoffmann modificado es útil para la evaluación de poblaciones con dificultades para su estudio como la pediátrica (AU)

Serum calcium (Ca), phosphorus (P), and alkaline phosphatase (AP) levels are broadly assessed in pediatrics. The procedure recommended by the International Federation of Clinical Chemistry (IFCC) for measuring AP in the Cobas 501 of Roche required reassessment of the reference interval (RI) in our pediatric population. The indirect method of Hoffmann with modifications proposed by Katayev et al. provides a mechanism to estimate the RI in difficult-to-study populations, such as children. Based on our data base, we aimed at determining the RI for Ca, P, and AP divided by age and sex (in the case of AP) in our pediatric population. One-year results of the hospital data base of subjects between 0 and 18 years of age were used. A total of 13.906 patients were analyzed for Ca, 14,790 for Ph, and 6,333 for AP. For AP sexual dimorphism was found in the age groups 7 to 9, 10 to 12, 13 to 15, and 16 to 18 years with a significant difference (p<0.0001). RIs were calculated with recommendations for age and sex. The analytes Ca and P did not show differences according to age, and differences according to sex were not significant although they were useful to determine ranges relative to AP. The modified Hoffmann method is useful in the evaluation of difficult-to-study populations, such as children (AU)

Pseudohipoparatiroidismo en niños, Manifestaciones clínicas e implicancias del tratamiento / Pseudohypoparathyroidism in childhood. Clinical manifestations and implications of treatment

El pseudohipoparatiroidismo es una enfermedad hereditaria caracterizada por presentar resistencia a la hormona paratiroidea que se manifiesta por hipocalcemia, hiperfosfatemia y niveles elevados de PTH. Los pacientes pueden presentar características fenotípicas de osteodistrofia hereditaria de Albright y tener asociadas otras resistencias hormonales. En este trabajo se analizan las características clínicas y bioquímicas de 13 niños afectados de la enfermedad, como así también la implicancia del tratamiento. El diagnóstico temprano, la detección oportuna de resistencias hormonales asociadas y el control periódico de los pacientes, son de relevancia para promover el crecimiento y disminuir las secuelas de la hipocalcemia (AU)

Pseudohypoparathyroidism is an hereditary disease characterized by hypocalcemia, hyperphosphatemia due to parathyroid hormone resistance. Patients may have the association of other endocrine resistances and physical characteristics termed Albright's hereditary osteodystrophy. We present here 13 patients with PHP, their clinic and biological signs, and the implication of the treatment. Early diagnosis, the study of other hormone resistances, and periodic control of the patients, are mandatory to promote a correct growth and decrease the consequences of hypocalcemia in these patients (AU)

Bone mineral density in children with celiac disease. Effect of a Gluten-free diet.

OBJECTIVE: To assess the degree of osteopenia in children with celiac disease (CD) at the time of diagnosis and the effect of a gluten-free diet (GFD). DESIGN: Longitudinal and prospective study. SUBJECTS: In total, 24 children (18 girls, six boys) diagnosed with CD by means of an intestinal biopsy were included in the study. Mean+/-s.d. age was 4.9+/-4.3 years. In all, 16 patients were under (2.20+/-0.82 year) and eight were over the age of 4 years (10.30+/-2.90 year). The time between the first symptoms and diagnosis was 17.30+/-24.70 months (range: 2-109 months). Spine bone mineral content (BMC), area and bone mineral density (BMD) were measured by DXA at baseline and 1.17+/-0.93 years after GFD. RESULTS: Before treatment, mean+/-s.d. BMD was 0.46+/-0.13 g/cm(2), the BMD Z-score was -1.36+/-1.20, and was below -1 s.d. in 14 patients (58%). BMC, area and BMD increased significantly on GFD. BMD increased from 0.46+/-0.13 to 0.55+/-0.13 g/cm(2) (P<0.001). BMD Z-score improved from -1.36+/-1.20 to -0.23+/-1.20 after GFD. However, BMD increased more than 1 s.d. in 15 of the 16 children under the age of 4 years, a similar increase was only observed in four of the eight children aged more than 4 years, some of whom did not follow GFD strictly. Height and weight increased significantly with GFD (P<0.001) and the increase correlated positively with the increase in BMD. CONCLUSIONS: Axial BMD below -1 s.d. was found in 58% of children with celiac disease. Axial bone mass reverted to normal values in most children under the age of 4, who had low bone mass, all of whom followed GFD strictly.

Evolución de niños post-trasplante hepático luego del primer año de sobrevida / Evolution of children one year post liver transplant

Orthotopic liver transplantation is the only definitive mode of therapy for children with end-stage liver disease. However, it remains challenging because of the necessity to prevent long-term complications. The aim of this study was to analyze the evolution of transplanted patients with more than one year of follow up. Between November 1992 and November 2001, 238 patients underwent 264 liver transplantations. A total of 143 patients with more than one year of follow up were included. The median age of patients +/- SD was 5.41 years +/- 5.26 (r: 0.58-21.7 years). All children received primary immunosuppression with cyclosporine. The indications for liver replacement were: fulminant hepatic failure (n: 50), biliary atresia (n: 38), cirrhosis (n: 37), chronic cholestasis (n: 13) and miscellaneous (n: 5). The indications for liver re-transplantation were: biliary cirrhosis (n: 7), hepatic artery thrombosis (n: 4) and chronic rejection (n: 3). Reduced-size liver allografts were used in 73/157 liver transplants, 14 of them were from living-related donors and 11 were split-livers. Patient and graft survival rates were 93% and 86% respectively. Death risk was statistically higher in retransplanted and reduced-size grafted patients. Growth retardation and low bone density were recovered before the first 3 years post-transplant. The incidence of lymphoproliferative disease was 7.69%. De novo hepatitis B was diagnosed in 7 patients (4.8%). Social risk did not affect the outcome of our population. The prevention, detection and early treatment of complications in the long-term follow up contributed to improve the outcome.

Evolución de niños post-trasplante hepático luego del primer año de sobrevida / Evolution of children one year post liver transplant

Orthotopic liver transplantation is the only definitive mode of therapy for children with end-stage liver disease. However, it remains challenging because of the necessity to prevent long-term complications. The aim of this study was to analyze the evolution of transplanted patients with more than one year of follow up. Between November 1992 and November 2001, 238 patients underwent 264 liver transplantations. A total of 143 patients with more than one year of follow up were included. The median age of patients +/- SD was 5.41 years +/- 5.26 (r: 0.58-21.7 years). All children received primary immunosuppression with cyclosporine. The indications for liver replacement were: fulminant hepatic failure (n: 50), biliary atresia (n: 38), cirrhosis (n: 37), chronic cholestasis (n: 13) and miscellaneous (n: 5). The indications for liver re-transplantation were: biliary cirrhosis (n: 7), hepatic artery thrombosis (n: 4) and chronic rejection (n: 3). Reduced-size liver allografts were used in 73/157 liver transplants, 14 of them were from living-related donors and 11 were split-livers. Patient and graft survival rates were 93% and 86% respectively. Death risk was statistically higher in retransplanted and reduced-size grafted patients. Growth retardation and low bone density were recovered before the first 3 years post-transplant. The incidence of lymphoproliferative disease was 7.69%. De novo hepatitis B was diagnosed in 7 patients (4.8%). Social risk did not affect the outcome of our population. The prevention, detection and early treatment of complications in the long-term follow up contributed to improve the outcome.(AU)

Niveles circulantes de 25 - hidroxivitamina D en población materno-infantil de zonas de riesgo del país: provincias de Chubut, Santa Cruz y Tierra del Fuego / Blood levels of 25-hidroxivitamine D in mothers and children of provinces at risk in Argentina: Chubut, Santa Cruz and Tierra del Fuego

Con el fin de evaluar el estado nutricional de vitamina D en el sur del país, se midieron niveles séricos de 25 hidroxivitamina D (250HD). Al final del invierno, se estudiaron 20 niños sanos en Comodoro rivadavia (Chubut. Latitud 45ºS, edad (X más menosDS) 2.2 más menos 0.99 años) y 51 niños sanos en Ushuaia, (tierra del Fuego, Latitud 54ºS, edad: 6.2 más menos 3.7años)Además en Rio Gallegos (Santa Cruz , latitud 52ºS) se estudiaron 27 madres sanas y cordón umbilical en el momento de parto. En Comodoro Rivadavia el 45% de los niños presentó deficiencia (<10ng/ml, n=9) y 5 niños insuficiencia de 250HD (10-15 ng/ml). La X más menos DS de todo el grupo fue: 12.6 más menos 4.7 ng/ml. En Ushuaia el promedio del todo gupo fue 20.6 más menos 8.5 ng/ml, 14 niños (27%) tuvieron valores de 250HD <15 ng/ml, la mayoria de los niños no habían recibido suplemento de vitamina D durante el invierno. Niños suplementados seis meses previos al estudio con 100.000 y 150.000 UI de vitamina D tuvieron valores mayores que los no suplementados (23.4 más menos 8.0 ng/ml, n=36 vs 14.1 más menos 5.5 ng/ml,n=15, p<0.001). Cinco de los niños suplementados presentaron valores de deficienica. La ingesta de calcio fue menos a la recomendada por FDA: 730 más menos230 mg/día. En Rio Gallegos el 66% de las madres y el 85% de los sueros de Cordón Umbilical presentaron niveles deficientes de 250HD. Estos resultados muestran que aún existe deficiencia de vitamina D en la población de niños saludables en el sur de nuestro país. En ushuaia, a pesar que los niveles circulantes de 250HD fueron mejores que en el resto, el hecho de que algunos niños suplementados presentaron niveles de deficiencia de vitamina D, sugiere la necesidad de implementar suplementos periódicos durante el invierno. Palabras clave: Vitamina D, enfermedad nutricional ó metabolica, raquitismo, 25-hidroxivitamina D, calcifediol.

Tolerancia y eficacia de calcipotriol ungüento en niños de 2 a 14 años con psoriasis vulgar / Tolerance and efficacy of calpotriol ointment in psoriasis vulgaris in children aged 2 - 14 años

El calcipotriol, un análogo de la vitamina D, es un tratamiento eficaz y seguro para la psoriasis en placas de carácter leve a moderado en pacientes adultos. Objetivos: Evaluar la eficacia y tolerancia del ungüento de calcipotriol en el tratamiento tópico de la psoriasis en niños. Determinar la influencia del mismo sobre el metabolismo cálcico y la presencia de efectos adversos. Materiales y métodos: 14 niños con psoriasis vulgar con menos del 30% de superficie corporal comprometida fueron tratados durante 8 semanas con calcipotriol ungüento 2 veces por día. Se evaluaron clínicamente a través del PASI la extensión y severidad de la enfermedad la eficacia clínica global y la tolerancia de la medicación. Se realizaron estudios de laboratorio (hematología, función renal, hepática, calcio sérico y urinario, fósforo, PTH y 25 hidroxivitamina D, antes de iniciar el tratamiento y las cuatro semanas. Resultados: 14 niños completaron el estudio, 7 mujeres y 7 varones. La edad promedio fue de 9 años. El PASI diminuyó en el 71%. No se detectaron efectos adversos a excepción de un leve ardor en dos pacientes. No hubo alteraciones de los parámetros de laboratorio incluyendo aquellos relacionados con la homeostasis del calcio. La tolerancia de la medicación fue excelente. Conclusiones: El ungüento de calcipotriol es un tratamiento seguro y eficaz para la psoriasis infantil. Constituye una terapéutica aceptable y útil junto a otros tratamientos antipsoriáticos furante la infancia.

Trasplante hepático. Seguimiento a largo plazo / Liver transplantation. Long term follow up

El trasplante hepático (TH) constituye la única alternativa terapéutica para numerosas enfermedades hepáticas avanzadas. Los adelantos en la técnica quirúrgica y en la inmunosupresión desarrollados en los últimos años permitieron mejorar la sobrevida. En la evolución a largo plazo de los pacientes trasplantados pueden presentarse complicaciones de diversa severidad. Objetivo: analizar la evolución a largo plazo de los pacientes trasplantados con un seguimiento mayor de 1 año post-TH. Material y Métodos: Durante el período 11/92-11/01 se realizaron 264 TH en 238 pacientes. De estos pacientes 143 (157 TH) fueron seguidos más allá de un año post-TH. La mediana de edad (m.a más menos DS) fue de 5,41 años más menos 5,26 (r:0.58 - 21.7 años); 76 pertenecían al sexo femenino. Catorce (9.79 por ciento) recibieron un re-TH. Fueron excluidos los pacientes que no habían cumplido todavía un años post- TH o los que fallecieron antes de ese lapso de seguimiento. Las indicaciones de TH fueron: falla hepática fulminante (FHF) (n:50); atresia de vías biliares (AVB) (n:38); cirrosis (n: 37); colestasis crónica (n: 13) y otras (n: 5). Las indicaciones de Re-TH fueron: cirrosis biliar (n: 7); trombosis de la arteria hepática (n: 4) y rechazo crónico (n: 3). En 73/157 TH se utilizaron injertos reducidos: 14 donantes vivos relacionados (DVR) y 11 biparticiones hepáticas. Se sometieron a análisis estadístico variables potenciales de morbimortalidad. Resultados: La sobrevida global fue: pacientes 93 por ciento: injerto: 86 por ciento. El re-TH y el injerto reducido fueron las variables de mayor significación para aumento del riesgo de muerte en nuestra población. El déficit de talla y masa ósea se recuperó anes de los 3 años post-TH. La incidencia del síndrome linfoproliferativo (SLP) fue del 7.69 por ciento, su diagnóstico y tratamiento temprano permitió una evolución favorable en la mayoria de los casos.

Mutational analysis of PHEX gene in X-linked hypophosphatemia.

Hypophosphatemic rickets is commonly an X-linked dominant disorder (XLH or HYP) associated with a renal tubular defect in phosphate transport and bone deformities. The XLH gene, referred to as PHEX, or formerly as PEX (phosphate regulating gene with homologies to endopeptidases on the X-chromosome), encodes a 749-amino acid protein that putatively consists of an intracellular, transmembrane, and extracellular domain. PHEX mutations have been observed in XLH patients, and we have undertaken studies to characterize such mutations in 46 unrelated XLH kindreds and 22 unrelated patients with nonfamilial XLH by single stranded conformational polymorphism and DNA sequence analysis. We identified 31 mutations (7 nonsense, 6 deletions, 2 deletional insertions, 1 duplication, 2 insertions, 4 splice site, 8 missense, and 1 within the 5' untranslated region), of which 30 were scattered throughout the putative extracellular domain, together with 6 polymorphisms that had heterozygosity frequencies ranging from less than 1% to 43%. Single stranded conformational polymorphism was found to detect more than 60% of these mutations. Over 20% of the mutations were observed in nonfamilial XLH patients, who represented de novo occurrences of PHEX mutations. The unique point mutation (a-->g) of the 5'untranslated region together with the other mutations indicates that the dominant XLH phenotype is unlikely to be explained by haplo-insufficiency or a dominant negative effect.

Panostotic fibrous dysplasia. A new craniotubular dysplasia.

The authors describe the radiographic-scintigraphic features of an unusual craniotubular dysplasia characterized by diffuse osteopenia with bone expansion and a "ground glass" appearance, markedly increased skeletal turnover, myelofibrosis, hypophosphatemia, and pigmented "coast-of-Maine" patches. This syndrome, termed panostotic fibrous dysplasia, is distinct from previously reported disorders.

[Dysregulation of plasma 1,25(OH)2D in calcium restriction in hypercalciuric children]. / Dysrégulation du 1,25(OH)2D plasmatique au cours d'une restriction calcique chez des enfants hypercalciuriques.

BACKGROUND: The effect of calcium restriction on the plasma concentration of 1,25(OH)2D in normo- and hypercalciuric children remains unknown. METHODS: We studied phosphate and calcium metabolism of 8 normocalciuric and 8 hypercalciuric children aged 4 to 16 years, under 3 conditions: on a normal dietary calcium intake after a 5-day calcium-restricted diet, and after oral calcium loading. The healthy, normocalciuric children had histories that included no renal failure of abnormalities of phosphate and calcium metabolism. Four of the 8 hypercalciuric children had urolithiasis, 1 had hematuria and the 3 others had idiopathic hypercalciuria. Blood samples were analyzed for calcium, creatinine, immunoreactive parathyroid hormone, cAMP, 25(OH)D and 1,25(OH)2D concentrations. Urine samples were analyzed for calcium, phosphorus, creatinine and cAMP. RESULTS: On the normal dietary calcium intake, the hypercalciuric children had higher urinary calcium excretion and plasma 1,25(OH)2D levels and lower TmP that did the controls. The 1,25(OH)2D levels of the normocalciuric children were significantly increased after 5 days of dietary calcium deprivation, but those of the hypercalciuric children were not. The other parameters (essentially PTH, cAMP and TmP) varied similarly in the two groups. CONCLUSION: The results suggest that: a) calcium restriction influences 1,25(OH)2D levels in normocalciuric subjects via a PTH- and phosphor-independent mechanism; b) dietary control of renal vitamin D metabolism is impaired in hypercalciuric patients.

Evidence for extrarenal production of 1,25-dihydroxyvitamin during physiological bone growth: in vivo and in vitro production by deer antler cells.

The development of deer antler follows a pattern similar to that described for mammalian endochondral ossification and has been proposed as a suitable model for studies of bone growth. We investigated seasonal changes in the plasma concentrations of 1,25-dihydroxyvitamin D [1,25-(OH)2D] and calcium and the activity of alkaline phosphatase in relation to the antler cycle during 1 yr in 4 captive roe deer and measured these biological parameters in 27 wild roe deer during their antler cycle. A significant elevation of 1,25-(OH)2D in peripheral plasma, with no parallel increase in the concentration of its precursor 25-hydroxyvitamin D, was observed to accompany the rapid growth phase of the antler cycle in captive (P less than 0.001) and wild (P less than 0.025) deer. During the same phase there was a gradient in levels of 1,25-(OH)2D in antler vs. jugular blood (P less than 0.01). In addition, velvet cells in culture proved to have the ability to convert 25-hydroxyvitamin D3 into a more polar derivative, which was indistinguishable from true 1,25-(OH)2D3 with regard to its chromatographic properties, its UV absorbance at 254 nm, and its ability to bind to the 1,25-(OH)2D3 receptors present in chick intestinal cytosol. These in vivo and in vitro results strongly suggest that local production of 1,25-(OH)2D by the antler cells does occur in vivo and may contribute to the increase in plasma 1,25-(OH)2D during bone growth.

[Prophylaxis of vitamin D deficiency in hypothyroidism in the newborn infant]. / Prophylaxie de la carence en vitamine D chez le nouveau-né hypothyroïdien.

This study deals with the relationship between the occurrence of hypercalcemia and the administration of prophylactic doses of vitamin D in children with hypothyroidism, before and during L-thyroxine (LT4) treatment. The goal of the study was to determine the dosage of vitamin D necessary to prevent rickets without inducing hypercalcemia. There was a 23% prevalence of hypercalcemia at the time of the diagnosis of hypothyroidism by screening whereas it was 21% in the children who were not given vitamin D during the first 3 months of LT4 treatment. This figure was significantly higher in those who were given vitamin D during the first 3 months of treatment and reached 70%. However, one of the 19 children not given vitamin D presented with biological signs evoking vitamin D deficiency. In conclusion, in hypothyroid infants, vitamin D should be administered carefully during the first 6 months of treatment and restricted to children at risk for developing vitamin D deficiency.

Corticosteroid-induced changes in the responsiveness of human osteoblast-like cells to parathyroid hormone.

We investigated the in vitro effect of corticosteroids on the responsiveness of human cells of osteoblast lineage to parathyroid hormone (PTH). Prior to corticosteroid treatment, the cells demonstrated only a small increase in cAMP production and no measurable change in transmembrane potential in response to PTH. Exposure of cells to dexamethasone resulted in a 5-fold increase in PTH-induced cAMP production and in measurable PTH-induced membrane depolarization in all cells studied. The effect of corticosteroids on cAMP production was specific for PTH (not seen with PGE1 or forskolin), occurred in a time- and dose-dependent fashion and in the absence of cell proliferation. Most of the cells were of osteoblast lineage as determined by the presence of alkaline phosphatase activity and BGP secretion. These findings further support the idea that corticosteroids increase the sensitivity of cells of osteoblast lineage to PTH, perhaps by transforming cells which initially have a low responsiveness to PTH to a state of high responsiveness.

[Extrarenal synthesis of calcitriol in sarcoidosis]. / Synthèse extra-rénale du calcitriol dans la sarcoïdose.

Mean plasma calcitriol was significantly increased in a patient with sarcoidosis and hypercalcemia without elevation of PTH. Recent studies provided evidence for an extrarenal production of calcitriol. To investigate this possibility, the conversion of calcidiol by a sarcoid lymph node homogenate was studied. After 2-hour incubation, a product was present in the incubation, which comigrated with synthetic calcitriol on two high performance liquid chromatography systems, was detected by ultraviolet absorption spectrometry and was bound with high affinity by the chick intestinal receptor for calcitriol. These results provide further evidence for an extrarenal synthesis of calcitriol, contributing to the excessive amounts of this metabolite found in the plasma of patients with sarcoidosis.

Hypercalcemia in infants with congenital hypothyroidism and its relation to vitamin D and thyroid hormones.

The circulating concentrations of calcium, phosphorus, and vitamin D metabolites were measured in 25 infants (fifteen to 30 days of age) with congenital hypothyroidism before treatment or during the first 6 months of thyroxine therapy. Five of the children before treatment and four during the early 3 months of treatment had mild hypercalcemia (10.8 to 12.4 mg/dl). Hypercalcemia before treatment did not appear to be related to the vitamin D status of the infant nor to an alteration in vitamin D metabolism, but to the presence of a residual thyroid secretion. In contrast, hypercalcemia during thyroxine therapy was related to vitamin D supplementation, even though the serum calcium concentration could not be correlated with the circulating concentration of any of the vitamin D metabolites assayed and obvious changes in vitamin D metabolism could not be demonstrated.

Long-term nocturnal calcium infusions can cure rickets and promote normal mineralization in hereditary resistance to 1,25-dihydroxyvitamin D.

We report the beneficial effects of calcium infusions in a child with hereditary resistance to 1,25(OH)2D and alopecia. This patient after transient responsiveness to vitamin D derivatives became unresponsive to all therapy despite serum 1,25(OH)2D concentrations maintained at levels approximately 100-fold normal. A 7-mo trial with calcium infusions led to correction of biochemical abnormalities and healing of rickets. Bone biopsies (n = 3) showed a normal mineralization and the disappearance of the osteomalacia. Cultures of bone-derived cells demonstrated a lack of activation of 25-hydroxyvitamin D 24-hydroxylase and osteocalcin synthesis by 1,25(OH)2D3 (10(-9) and 10(-6) M). These results demonstrate that even in the absence of a normal 1,25(OH)2D3 receptor-effector system in bone cells, normal mineralization can be achieved in humans if adequate serum calcium and phosphorus concentrations are maintained; and calcium infusions may be an efficient alternative for the management of patients with this condition who are unresponsive to large doses of vitamin D derivatives.

Response to parathyroid hormone and 1,25-dihydroxyvitamin D3 of bone-derived cells isolated from normal children and children with abnormalities in skeletal development.

In order to evaluate the role of intrinsic defects in osteoblast function in the pathogenesis of diseases of skeletal development, we developed techniques which permit the evaluation of the metabolic properties of bone-derived cells in vitro. Cells from control children demonstrated a variety of properties classically attributed to osteoblasts (presence of alkaline phosphatase positive cells and synthesis of bone gla protein) and responded to PTH (cAMP production) and to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) ([3H]25-hydroxyvitamin D3 conversion into [3H]24,25-dihydroxyvitamin D3 and bone gla protein secretion). Using these techniques we evaluated the function of cultured bone cells from patients with three rare diseases of skeletal development. Cells from a patient with rickets resistant to 1,25(OH)2D3 were resistant to 1,25(OH)2D3 but responded normally to PTH. Cells from a patient with acroosteolysis with osteoporosis responded normally to PTH and 1,25(OH)2D3. Cells from a patient with hyperphosphatasia with osteoectasia responded normally to 1,25(OH)2D3 but did not respond to PTH. The results demonstrate that bone cell cultures can provide information about the role of osteoblast dysfunction in such diseases.

Contenido mineral oseo en la poblacion normal de Buenos Aires / Mineral bone content in a normal population of Buenos Aires

El contenido mineral oseo fue determinado en el tercio medio del radio en 209 sujetos normales de ambos sexos. El metodo empleado se funda en la absorcion de fotones emitidos por una fuente de 100 mCi de 241 Am. El coeficiente de variacion para la lectura de un estandard fue de 0,98% y para un sujeto al que se le practicaron 10 mediciones sucesivas de 1,9% . El contenido mineral mas elevado se observo en las mujeres durante la cuarta decada y en los hombres en la quinta decada. A partir de dicha edad la masa osea disminuye, observandose en las mujeres una caida promedio de 19,5% y en los hombres de 12,8% hasta el comienzo de la octava decada. Los valores obtenidos constituyen un estandard de referencia para la evaluacion clinica de pacientes con osteopatias desmineralizantes o condensantes