Mice deficient in Abl are osteoporotic and have defects in osteoblast maturation

The c-Abl protein is a non-receptor tyrosine kinase involved in many aspects of mammalian development. c-Abl kinase is widely expressed, but high levels are found in hyaline cartilage in the adult, bone tissue in newborn mice, and osteoblasts and associated neovasculature at sites of endochondrial ossification in the fetus. Mice homozygous for mutations in the gene encoding c-Abl (AIM) display increased perinatal mortality, reduced fertility, foreshortened crania and defects in the maturation of B cells in bone marrow. Here we demonstrate that Abl-/- mice are also osteoporotic. The long bones of mutant mice contain thinner cortical bone and reduced trabecular bone volume. The osteoporotic phenotype is not due to accelerated bone turnover--both the number and activity of osteoclasts are similar to those of control littermates--but rather to dysfunctional osteoblasts. In addition, the rate of mineral apposition in the mutant animals is reduced. Osteoblasts from both stromal and calvarial explants showed delayed maturation in vitro as measured by expression of alkaline phosphatase (ALP), induction of mRNA encoding osteocalcin and mineral deposition.

Osteopetrosis in mice lacking haematopoietic transcription factor PU.1

Osteoclasts are multinucleated cells and the principal resorptive cells of bone. Although osteoclasts are of myeloid origin, the role of haematopoietic transcription factors in osteoclastogenesis has not been explored. Here we show that messenger RNA for the myeloid- and B-cell-specific transcription factor PU.1 progressively increases as marrow macrophages assume the osteoclast phenotype in vitro. The association between PU.1 and osteoclast differentiation was confirmed by demonstrating that PU.1 expression increased with the induction of osteoclastogenesis by either 1,25-dihydroxyvitamin D3 or dexamethasone. Consistent with the participation of PU.1 in osteoclastogenesis, we found that the development of both osteoclasts and macrophages is arrested in PU.1-deficient mice. Reflecting the absence of osteoclasts, PU.1-/- mice exhibit the classic hallmarks of osteopetrosis, a family of sclerotic bone diseases. These animals were rescued by marrow transplantation, with complete restoration of osteoclast and macrophage differentiation, verifying that the PU.1 lesion is intrinsic to haematopoietic cells. The absence of both osteoclasts and macrophages in PU.1-mutant animals suggests that the transcription factor regulates the initial stages of myeloid differentiation, and that its absence represents the earliest developmental osteopetrotic mutant yet described.

[Prefrontal dementias: clinical features and SPECT in 6 cases]

Six patients with primary degenerative dementias and frontal or frontotemporal hypoperfusion are reported. Five were diagnosed as Frontal Progressive Dementia (FPD), characterized by striking changes in personality and social behavior. The last patient had a progressive aphasia and a moderate cognitive impairment. We discuss the heterogeneity of FPD that includes Pick's disease, frontal lobe type dementia (Neary) and progressive subcortical gliosis. The usefulness of SPECT and the need of a brain bank are remarked.

[Sneddon syndrome. Presentation of 2 cases]

Sneddon syndrome is a systemic non inflammatory arteriopathy characterized by the association of livedo reticularis, thrombotic cerebrovascular disease, coronary artery disease and hypertension. Middle age females are usually affected. It should be considered in the differential diagnosis of acute ischemic attacks in younger patients. It has been related to the antiphospholipid antibody syndrome. Treatment is based on control of hypertension and cardiovascular risk factors along with antiplatelet agents. Two cases meeting the clinical criteria outlined above are reported.

Relationship between the tonic elevator mandibular activity and the vertical dimension during the states of vigilance and hypnosis

The variation of the tonic EMG elevator mandibular activity was studied as well as the consequent variation of the vertical dimension in two different experimental states: those of vigilance and hypnosis. In the state of vigilance, normal values of tonic EMG activity were recorded and a space of inocclusion (X = 2.22 mm) coincident with the postural mandibular position. Under hypnosis a significant reduction of the tonic EMG activity was observed (43 to 50%), together with a great increase of the inocclusion space (X = 8.90 mm).

[Alzheimer-type dementia: clinical experience in 71 cases]

The clinical criteria used for making the diagnosis of dementia of the Alzheimer type are featured, presenting the experience with 71 patients who fulfilled those prerequisites. The manifestations began generally over the age of 60, predominantly in females, and frequently there was a history of affection in other family members. The symptoms most frequently found were memory defects, lack of abstraction and anosognosia. The diagnosis depended most often on the clinical findings rather than the laboratory studies, which could be normal. It is worth noting the variable clinical courses found indicating that we are dealing with a heterogeneous population. It is suggested that dementia of the Alzheimer type and normal senility are not contrasting conditions but rather a continuum of the same process.