We analyzed the effect of substituting serine for each of the 19 cysteine residues within the amino-terminal extracellular domain of the human Ca 2؉ receptor on cell surface expression and receptor dimerization. C129S, C131S, C437S, C449S, and C482S were similar to wild type receptor; the other 14 cysteine to serine mutants were retained intracellularly. Four of these, C60S, C101S, C358S and C395S, were unable to dimerize. A C129S/C131S double mutant failed to dimerize but was unique in that the monomeric form expressed at the cell surface. Substitution of a cysteine for serine 132 within the C129S/C131S mutant restored receptor dimerization. Mutation of residues Cys-129, Cys-131, and Ser-132, singly and in various combinations caused a left shift in Ca 2؉ response compared with wild type receptor. These results identify cysteines 129 and 131 as critical in formation of intermolecular disulfide bond(s) responsible for receptor dimerization. In a "venus flytrap" model of the receptor extracellular domain, Cys-129 and Cys-131 are located within a region protruding from one lobe of the flytrap. We suggest that this region represents a dimer interface for the receptor and that mutation of residues within the interface causes important changes in Ca 2؉ response of the receptor.

The presence of macroprolactinaemia does not exclude the possibility of a pituitary adenoma and consequently may not prevent pituitary imaging studies. However, our data demonstrate that all asymptomatic patients who screened positive for macroprolactin had normal pituitary imaging studies. Patient samples showing hyperprolactinaemia should be first tested for macroprolactin, before the patient is submitted to imaging studies. We suggest that imaging studies should be ordered in patients with macroprolactinaemia when indicated by clinically relevant features. As a result, unnecessary anxiety and costly medical procedures may be prevented.

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CONTEXT: It is believed that about 25% of menopausal women in the USA will exhibit some kind of fracture as a consequence of osteoporosis. Fractures of the proximal femur are associated with a greater number of deaths and disabilities and higher medical expenses than all the other osteoporotic fractures together. OBJECTIVE: To study the clinical and epidemiological features of patients with proximal femur fracture in hospitals in São Paulo. DESIGN: Transversal and retrospective study. LOCAL: Hospital São Paulo and Hospital Servidor Público Estadual "Francisco Morato Oliveira". PARTICIPANTS: Patients aged sixty-five years or more hospitalized because of proximal femur fracture, from March to November 1996 (N = 73). This group was compared to patients of the same age without fracture of the proximal femur. INTERVENTION: Evaluation of weight, height, body mass index; lifestyle habits (physical activity at home, ingestion of dairy calcium, drinking of coffee, smoking habit), gynecological history (ages at menarche and menopause, number of pregnancies and lactations), previous morbidity, use of medications, history of previous fractures, family history of osteoporosis. MEASUREMENT: The comparison of the different data regarding lifestyle habits between the two groups was made using the chi-squared test. Other data were analyzed using the Mann -- Whitney test. P £ 0.05 was considered significant. RESULTS: We noted a predominance of proximal femur fracture among females in relation to males (a female/male ratio of 3.3:1) with a progressive increase in the frequency of proximal femur fracture with age in both sexes. The group with proximal femur fracture, in comparison with the control group, showed a lower body mass index, less physical activity, and a greater number of pregnancies and lactations. Other data were not different. CONCLUSION: In accordance with the literature, we found a predomination of proximal femur fracture in women in relation to men, and a favorable effect of higher body mass index and physical activity for decreasing the frequency of proximal femur fracture. We also discuss the role of pregnancies and lactation on the frequency of proximal femur fracture.

A missense mutation, A843E, in the seventh transmembrane domain of the human Ca P+ receptor, identified in a subject with autosomal dominant hypocalcemia, was found to cause a constitutive activation while at the same time lowering the maximal response of the receptor to Ca

Naturally occurring mutations identified in subjects with autosomal dominant hypocalcemia (ADH) and the calcimimetic compound, R-568, have both been reported to increase Ca2+ sensitivity of the Ca2+ receptor (CaR). To gain insight into their mechanism of action, we studied interactions between four different ADH mutations located in the amino-terminal extracellular domain (ECD) and R-568. We found that R-568 increased the sensitivity of three of the ADH mutant receptors, but the Leu125Pro mutant appeared to be maximally left-shifted in that neither R-568 addition nor combining other ADH mutations with Leu125Pro gave increases in sensitivity comparable to those seen with the three other ADH mutations studied. We also made use of truncation and deletion mutants of the CaR and CaR/metabotropic glutamate receptor type 1 (mGluR1) chimeras to study both the site of action of R-568 and the effect of the Leu125Pro activating mutation. R-568 was effective in receptor constructs containing the seven transmembrane domain (7TM) of the CaR, but not in those containing the mGluR1 7TM. R-568, moreover, imparted Ca2+ responsiveness to CaR constructs lacking all or part of the CaR ECD. The Leu125Pro mutation in contrast conferred no or minimal increase in Ca2+ responsiveness to CaR constructs lacking part of the CaR ECD but showed a striking increase in basal activity in the context of chimeras containing an mGluR1 7TM. Our results localize the site of action of NPS-568 specifically to the CaR 7TM. Our results with the Leu125Pro mutant, furthermore, suggest that the mGluR1 7TM domain may be more permissive for activation than the 7TM domain of the CaR.

RESUMOAs síndromes de neoplasias endócrinas múltiplas (NEM) incluem as do tipo 1 (MEN 1) e 2 (MEN 2), a síndrome de von Hippel-Lindau, neurofibromatose tipo 1 e o complexo de Carney. Estas são síndromes genéticas complexas decorrentes de ativação ou inativação de diferentes tipos de genes envolvidos na regulação da proliferação celular. Nesta revisão, discutiremos as manifestações clínicas e o acompanhamento da MEN 1, assim como o rastreamento genético de potenciais portadores de alterações no gene MEN 1. A MEN 1 inclui o desenvolvimento de hiperparatiroidismo primário multifocal, tumores de ilhotas pancreáticas e adenomas de hipófise. Além disso, alguns pacientes podem apresentar manifestações cutâneas como angiofibromas e colagenomas e ainda podem desenvolver outras neoplasias como tumores carcinóides, tumores de tiróide, adenomas de adrenal, lipomas, feocromocitomas e meningiomas. A MEN 1 é uma síndrome hereditária, transmitida de forma autossômica dominante e causada por mutação inativadora do gene MEN 1. O gene MEN 1 codifica uma proteína denominada "menin", que é um gene supressor tumoral. Vários estudos demonstraram sua importância na regulação da proliferação celular e confirmaram seu papel na patogênese da MEN 1. A identificação do gene MEN 1 e sua análise genética resultaram na possibilidade de monitoração de pacientes que ainda não apresentam manifestações clínicas associadas a esta síndrome e diagnóstico precoce e tratamento dos pacientes afetados. Tais medidas poderão implicar em sobrevida maior para estes pacientes. Estudos adicionais visando uma melhor compreensão da função e dos mecanismos de sinalização da proteína "menin" poderão propiciar alternativas terapêuticas para os pacientes que evoluem com malignização de tumores relacionados à MEN 1, podendo resultar em maior sobrevida. Multiple endocrine neoplasia (MEN) syndromes include types 1 (MEN 1) and 2 (MEN 2), von Hippel-Lindau syndrome, neurofibromatosis type 1 and Carney complex. These are complex genetic syndromes caused by activation or inactivation of different types of genes known to be involved in the regulation of cell proliferation. In this review we will discuss the clinical manifestations and management of the MEN 1 syndrome as well as the genetic screening of potential MEN 1 gene carriers. MEN 1 is a hereditary syndrome, transmitted in an autosomic dominant fashion and caused by an inactivating mutation of the MEN 1 gene, characterized by the development of primary hyperparathyroidism, islet cell tumors and pituitary adenomas. In addition, these patients can pre-

Vitamin D deficiency, observed mainly in the geriatric population, is responsible for loss of bone mass and increased risk of bone fractures. Currently, recommended doses of cholecalciferol are advised, but since there are few studies evaluating the factors that influence the serum levels of 25-hydroxyvitamin D (25(OH)D) following supplementation, we analyzed the relationship between the increase in serum 25(OH)D after supplementation and body fat. We studied a group of 42 homebound elderly subjects over 65 years old (31 women) in order to assess whether there is a need for adjustment of the doses of cholecalciferol administered to this group according to their adipose mass. Baseline measurements of 25(OH)D, intact parathyroid hormone and bone remodeling markers (osteocalcin and carboxy-terminal fraction of type 1 collagen) were performed. Percent body fat was measured by dual-energy X-ray absorptiometry. The patients were divided into three groups according to their percent body fat index and were treated with cholecalciferol, 7,000 IU a week, for 12 weeks. The increases in serum levels of 25(OH)D were similar for all groups, averaging 7.46 ng/mL (P < 0.05). It is noteworthy that this increase only shifted these patients from the insufficiency category to hypovitaminosis. Peak levels of 25(OH)D were attained after only 6 weeks of treatment. This study demonstrated that adipose tissue mass does not influence the elevation of 25(OH)D levels following vitamin D supplementation, suggesting that there is no need to adjust vitamin D dose according to body fat in elderly homebound individuals.