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In the mammal, definitive hematopoietic stem cells (HSCs) are first derived from mesodermal cells within a region of the embryonic para-aortic splanchnopleura known as the aorta-gonad-mesonephros (AGM). Within this region, HSCs are thought to arise from hemangioblast precursors located in the ventral wall of the dorsal aorta. However, the factors that regulate HSC development in vivo are still largely unknown. Bone morphogenetic protein (BMP)-4, a member of the transforming growth factor beta (TGF-β) superfamily of growth factors, is a potent ventralizing factor and has been implicated in the commitment of embryonic mesodermal cells to a hematopoietic fate in a number of systems. In the human AGM, we find that BMP-4 is expressed at high levels, and with striking polarity, in a region of densely packed cells underlying intra-aortic hematopoietic clusters. In contrast, TGF-β1 is expressed predominantly by hematopoietic cells within the clusters. These findings implicate both BMP-4 and TGF-β1 in the initiation and regulation of hematopoiesis in the human AGM. Furthermore, the distribution of BMP-4 expression is highly suggestive of a direct role in the specification of human hematopoietic cells from embryonic mesoderm in vivo.

In the mammal, definitive hematopoietic stem cells (HSCs) are first derived from mesodermal cells within a region of the embryonic para-aortic splanchnopleura known as the aorta-gonad-mesonephros (AGM). Within this region, HSCs are thought to arise from hemangioblast precursors located in the ventral wall of the dorsal aorta. However, the factors that regulate HSC development in vivo are still largely unknown. Bone morphogenetic protein (BMP)-4, a member of the transforming growth factor beta (TGF-β) superfamily of growth factors, is a potent ventralizing factor and has been implicated in the commitment of embryonic mesodermal cells to a hematopoietic fate in a number of systems. In the human AGM, we find that BMP-4 is expressed at high levels, and with striking polarity, in a region of densely packed cells underlying intra-aortic hematopoietic clusters. In contrast, TGF-β1 is expressed predominantly by hematopoietic cells within the clusters. These findings implicate both BMP-4 and TGF-β1 in the initiation and regulation of hematopoiesis in the human AGM. Furthermore, the distribution of BMP-4 expression is highly suggestive of a direct role in the specification of human hematopoietic cells from embryonic mesoderm in vivo.

Objective: To estimate service demand (willingness to seek or use services) for respite care among informal, primary carers of people with a psychological disability and to describe their characteristics.Methods: Analysis of data from the household component of the 2009 Survey of Disability Ageing and Carers (n=64,213 persons). Results:In Australia in 2009, 1.0% of people aged 15 years or over (177,900 persons) provided informal, primary care to a co-resident with a psychological disability. One-quarter (27.2%) of these carers reported service demand for respite care, of whom one-third had used respite services in the past three months and four-fifths had an unmet need for any or more respite care. A significantly greater percentages of carers with service demand for respite care spent 40 or more hours per week on caregiving, provided care to a person with profound activity restrictions and reported unmet support needs, compared to carers without service demand. Lack of suitable, available respite care models was a barrier to utilisation. Conclusions:Findings confirm significant service demand for, and under-utilisation of, respite care among mental health carers.Implications: Increased coverage of respite services, more flexible service delivery models matched to carers' needs and better integration with other support services are indicated.