Atypical molecular profile for joint development in the avian costal joint

Development of synovial joints involves generation of cartilaginous anlagen, formation of interzones between cartilage anlagen, and cavitation of interzones to produce fluid filled cavities. Interzone development is not fully understood, but interzones are thought to develop from skeletogenic cells that are inhibited from further chondrogenic development by a cascade of gene expression including Wnt and Bmp family members. We examined the development of the rarely studied avian costal joint to better understand mechanisms of joint development. The costal joint is found within ribs, is morphologically similar to the metatarsophalangeal joint, and undergoes cavitation in a similar manner. In contrast to other interzones, Wnt14/9a, Gdf5, Chordin, Barx1, and Bapx1 are absent from the costal joint interzone, consistent with the absence of active β-catenin and phosphorylated Smad 1/5/8. However Autotaxin and Noggin are expressed. The molecular profile of the costal joint suggests there are alternative mechanisms of interzone development.

A new view of patterning domains in the vertebrate mesoderm

The musculoskeletal system of vertebrates is derived from the embryonic mesoderm. Its structures are categorized as epaxial or hypaxial based on their adult position and innervation. The epaxial/hypaxial terminology is also used to describe regions of the embryonic somites based on fate mapping of somitic derivatives. However, the adult, functional distinctions are not fully consistent with the changing embryonic environments of mesodermal populations during morphogenesis, and the traditional terminology loses accuracy when used to describe certain mutant phenotypes. Here we describe a new terminology naming two mesodermal environments defined by the lineage of the included cells. We discuss how mutant phenotypes may be better explained by consideration of the embryonic context in which genes take their effect and argue that the recognition of these embryonic territories clarifies description and discussion of the morphogenesis and patterning of the musculoskeletal system.

Assembly of trunk and limb blood vessels involves extensive migration and vasculogenesis of somite-derived angioblasts

Vascular development requires the assembly of precursor cells into blood vessels, but how embryonic vessels are assembled is not well understood. To determine how vascular cells migrate and assemble into vessels of the trunk and limb, marked somite-derived angioblasts were followed in developing embryos. Injection of avian somites with the cell-tracker DiI showed that somite-derived angioblasts in unperturbed embryos migrated extensively and contributed to trunk and limb vessels. Mouse-avian chimeras with mouse presomitic mesoderm grafts had graft-derived endothelial cells in blood vessels at significant distances from the graft, indicating that mouse angioblasts migrated extensively in avian hosts. Mouse graft-derived endothelial cells were consistently found in trunk vessels, such as the perineural vascular plexus, the cardinal vein, and presumptive intersomitic vessels, as well as in vessels of the limb and kidney rudiment. This reproducible pattern of graft colonization suggests that avian vascular patterning cues for trunk and limb vessels are recognized by mammalian somitic angioblasts. Mouse-quail chimeras stained with both the quail vascular marker QH1 and the mouse vascular marker PECAM-1 had finely chimeric vessels, with graft-derived mouse cells interdigitated with quail vascular cells in most vascular beds colonized by graft cells. Thus, diverse trunk and limb blood vessels have endothelial cells that developed from migratory somitic angioblasts, and assembly of these vessels is likely to have a large vasculogenic component.

Morphogenesis of the turtle shell: the development of a novel structure in tetrapod evolution

The turtle shell is an evolutionary novelty that is synapomorphic for chelonians. The carapace is initiated by the entrapment of the ribs by the carapacial ridge (CR), a lateral bulge of the dorsal ectoderm and dermal mesoderm. The mechanisms by which the CR is initiated, the ribs entrapped and the dorsal dermis ossified, remains unknown. Similarly, the formation of the plastron remains unexplained. Here, we present a series of anatomical investigations into plastron and carapace formation in the red-eared slider, Trachemys scripta, and the snapping turtle, Chelydra serpentina. We document the entrapment of the ribs by the CR and the formation of the plastron and carapacial bones by intramembranous ossification. We note the formation of the ossification centers around each rib, which suggest that the rib is organizing dermal ossification by secreting paracrine factors. The nuchal ossification center is complex and appears to involve multiple bone-forming regions. Individual ossification centers at the periphery of the carapace form the peripheral and pygial bones. The intramembranous ossification of the plastron proceeds from nine distinct ossification centers, and there appear to be interactions between the spicules of apposing centers as they draw near each other.

Hox genes and morphological identity: axial versus lateral patterning in the vertebrate mesoderm

The successful organization of the vertebrate body requires that local information in the embryo be translated into a functional, global pattern. Somite cells form the bulk of the musculoskeletal system. Heterotopic transplants of segmental plate along the axis from quail to chick were performed to test the correlation between autonomous morphological patterning and Hox gene expression in somite subpopulations. The data presented strengthen the correlation of Hox gene expression with axial specification and focus on the significance of Hox genes in specific derivatives of the somites. We have defined two anatomical compartments of the body based on the embryonic origin of the cells making up contributing structures: the dorsal compartment, formed from purely somitic cell populations; and the ventral compartment comprising cells from somites and lateral plate. The boundary between these anatomical compartments is termed the somitic frontier. Somitic tissue transplanted between axial levels retains both original Hox expression and morphological identity in the dorsal compartment. In contrast, migrating lateral somitic cells crossing the somitic frontier do not maintain donor Hox expression but apparently adopt the Hox expression of the lateral plate and participate in the morphology appropriate to the host level. Dorsal and ventral compartments, as defined here, have relevance for experimental manipulations that influence somite cell behavior. The correlation of Hox expression profiles and patterning behavior of cells in these two compartments supports the hypothesis of independent Hox codes in paraxial and lateral plate mesoderm.

Ideology and social work practice in substance abuse settings

The profession of social work has a unique role in preventing and treating alcohol and other drug problems. In human services settings shared beliefs or ideologies of care are expected to have substantial influence over the way in which problems are perceived and the types of service technologies used. Thus, it is important that social work professionals be cognizant of what beliefs they hold and how their beliefs about substance abuse treatment and prevention may affect practice. This article discusses current ideologies of care in the substance abuse arena, including the disease/abstinence, psychosocial, ecological, and harm-reduction approaches. In addition, this article examines managers' beliefs about substance abuse programs to determine if there are differences between those who have a social work background (that is, hold at least one social work degree) and those who do not. Suggestions for social work practice and future research also are provided.

Supervisor ideology and organizational response: HIV/AIDS prevention in outpatient substance abuse treatment units

Distinct practice ideologies or ideologies of care are deemed to influence greatly the selection of intervention methods and the mix of services adopted by the providers. Examined here is the relation between clinical supervisor ideology and variation among human service organizations in their provision of HIV/AIDS prevention services. Data were drawn from a 1990 national, representative sample of outpatient substance abuse treatment (OSAT) units. The study affirms that ideology is central to both means and ends in HSOs, helping to define the organization's mission and goals, and establishing guidelines for practice and procedures. Future research on the relationship between ideology and HIV/AIDS education can benefit from efforts to develop alternative strategies for measuring ideologies of care among both managers and staff in substance abuse settings.

Life after funding: a strategy for survival of a program to prevent substance abuse

Problems associated with the use of alcohol and other drugs are among the most serious public health threats found on college and university campuses in the United States. The United States Department of Education's Fund for the Improvement of Postsecondary Education program has supported a nationwide effort among colleges and universities to address these problems. A key issue facing programs to prevent substance abuse is their prospect for survival as grant funding ends. In this article, the survival of one college-based alcohol and other drug prevention program and its move toward institutionalization in an extremely challenging fiscal environment are examined. The strategies described by the authors may be helpful for directors of other programs facing similar challenges.

Virally mediated misexpression of Hoxc-6 in the cervical mesoderm results in spinal nerve truncations

Members of the Hox gene family appear to regulate anterior-posterior (A-P) regionalization in embryos. Genetic manipulation of numerous Hox genes in the developing trunk region of vertebrates results in changes in the morphology of individual vertebrae. We have used virally mediated, targeted misexpression to ectopically express the Hoxc-6 protein in chick embryos. Hoxc-6 has an anterior border of expression at the cervical-thoracic transition in tetrapods. Misexpression of this gene in the cervical mesoderm of chick embryos results in dramatic truncations of the ventral rami of cervical spinal nerves in the infected region. These data point to a role for Hoxc-6 in axon guidance, and suggest that in addition to regulating proliferative rates, Hox gene expression provides positional information utilized in producing domain-specific extracellular signals.

Analysis of Hox gene expression in the chick limb bud

The vertebrate Hox genes have been shown to be important for patterning the primary and secondary axes of the developing vertebrate embryo. The function of these genes along the primary axis of the embryo has been generally interpreted in the context of positional specification and homeotic transformation of axial structures. The way in which these genes are expressed and function during the development of the secondary axes, particularly the limb, is less clear. In order to provide a reference for understanding the role of the Hox genes in limb patterning, we isolated clones of 23 Hox genes expressed during limb development, characterized their expression patterns and analyzed their regulation by the signalling centers which pattern the limb. The expression patterns of the Abd-B-related Hoxa and Hoxd genes have previously been partially characterized; however, our study reveals that these genes are expressed in patterns more dynamic and complex than generally appreciated, only transiently approximating simple, concentric, nested domains. Detailed analysis of these patterns suggests that the expression of each of the Hoxa and Hoxd genes is regulated in up to three independent phases. Each of these phases appears to be associated with the specification and patterning of one of the proximodistal segments of the limb (upper arm, lower arm and hand). Interestingly, in the last of these phases, the expression of the Hoxd genes violates the general rule of spatial and temporal colinearity of Hox gene expression with gene order along the chromosome. In contrast to the Abd-B-related Hoxa and Hoxd genes, which are expressed in both the fore and hind limbs, different sets of Hoxc genes are expressed in the two limbs. There is a correlation between the relative position of these genes along the chromosome and the axial level of the limb bud in which they are expressed. The more 3′ genes are expressed in the fore limb bud while the 5′ genes are expressed in the hind limb bud; intermediate genes are transcribed in both limbs. However, there is no clear correlation between the relative position of the genes along the chromosome and their expression domains within the limb. With the exception of Hoxc-11, which is transcribed in a posterior portion of the hind limb, Hoxc gene expression is restricted to the anterior/proximal portion of the limb bud. Importantly, comparison of the distributions of Hoxc-6 RNA and protein products reveals posttranscriptional regulation of this gene, suggesting that caution must be exercised in interpreting the functional significance of the RNA distribution of any of the vertebrate Hox genes. To understand the genesis of the complex patterns of Hox gene expression in the limb bud, we examined the propagation of Hox gene expression relative to cell proliferation. We find that shifts in Hox gene expression cannot be attributed to passive expansion due to cell proliferation. Rather, phase-specific Hox gene expression patterns appear to result from a context-dependent response of the limb mesoderm to Sonic hedgehog. Sonic hedgehog (the patterning signal from the Zone of Polarizing Activity) is known to be able to activate Hoxd gene expression in the limb. Although we find that Sonic hedgehog is capable of initiating and polarizing Hoxd gene expression during both of the latter two phases of Hox gene expression, the specific patterns induced are not determined by the signal, but depend upon the temporal context of the mesoderm receiving the signal. Misexpression of Sonic hedgehog also reveals that Hoxb-9, which is normally excluded from the posterior mesenchyme of the leg, is negatively regulated by Sonic hedgehog and that Hoxc-11, which is expressed in the posterior portion of the leg, is not affected by Sonic hedgehog and hence is not required to pattern the skeletal elements of the lower leg.

Ideologies of care in community residential services: what do caregivers believe?

Ideologies of care, or systems of beliefs about the importance of particular goals and activities, help guide how care is provided. One currently pervasive ideology of care is that of normalization. In this paper, the ideologies of care of both house managers and direct care staff in group homes are contrasted. Results indicate that the ideology of direct care staff is less differentiated than that of the house managers. In addition, house managers are more likely to subscribe to a normalization ideology and less likely to subscribe to a family orientation ideology than are direct care staff. Ideological differences between house managers and direct care staff are only partially explained by differences in the demographic composition of the two groups.

Sonic hedgehog is an endodermal signal inducing Bmp-4 and Hox genes during induction and regionalization of the chick hindgut

Reciprocal inductive signals between the endoderm and mesoderm are critical to vertebrate gut development. Sonic hedgehog encodes a secreted protein known to act as an inductive signal in several regions of the developing embryo. In this report, we provide evidence to support the role of Sonic hedgehog and its target genes Bmp-4 and the Abd-B-related Hox genes in the induction and patterning the chick hindgut. Sonic is expressed in the definitive endoderm at the earliest stage of chick gut formation. Immediately subjacent to Sonic expression in the caudal endoderm is undifferentiated mesoderm, later to become the visceral mesoderm of the hindgut. Genes expressed within this tissue include Bmp-4 (a TGF-beta relative implicated in proper growth of visceral mesoderm) and members of the Abd-B class of Hox genes (known regulators of pattern in many aspects of development). Using virally mediated misexpression, we show that Sonic hedgehog is sufficient to induce ectopic expression of Bmp-4 and specific Hoxd genes within the mesoderm. Sonic therefore appears to act as a signal in an epithelial-mesenchymal interaction in the earliest stages of chick hindgut formation. Gut pattern is evidenced later in gut morphogenesis with the presence of anatomic boundaries reflecting phenotypically and physiologically distinct regions. The expression pattern of the Abd-b-like Hox genes remains restricted in the hindgut and these Hox expression domains reflect gut morphologic boundaries. This finding strongly supports a role for these genes in determining the adult gut phenotype. Our results provide the basis for a model to describe molecular controls of early vertebrate hindgut development and patterning. Expression of homologous genes in Drosophila suggest that aspects of gut morphogenesis may be regulated by similar inductive networks in the two organisms.

Hox genes and the evolution of vertebrate axial morphology

A common form of evolutionary variation between vertebrate taxa is the different numbers of segments that contribute to various regions of the anterior-posterior axis; cervical vertebrae, thoracic vertebrae, etc. The term ‘transposition’ is used to describe this phenomenon. Genetic experiments with homeotic genes in mice have demonstrated that Hox genes are in part responsible for the specification of segmental identity along the anterior-posterior axis, and it has been proposed that an axial Hox code determines the morphology of individual vertebrae (Kessel, M. and Gruss, P. (1990) Science 249, 347–379). This paper presents a comparative study of the developmental patterns of homeobox gene expression and developmental morphology between animals that have homologous regulatory genes but different morphologies. The axial expression boundaries of 23 Hox genes were examined in the paraxial mesoderm of chick, and 16 in mouse embryos by in situ hybridization and immunolocalization techniques. Hox gene anterior expression boundaries were found to be transposed in concert with morphological boundaries. This data contributes a mechanistic level to the assumed homology of these regions in vertebrates. The recognition of mechanistic homology supports the historical homology of basic patterning mechanisms between all organisms that share these genes.

Ownership differences in the provision of outpatient substance abuse services

The authors examine the assumption of the 1980s that the provision and costs of substance abuse services, among others, could best be met by expanding programs in the private sector. The study presents a comparison of public and private substance abuse services, based on data drawn from a national sample of outpatient units, and develops a profile of treatment and financing within three auspice (ownership) categories--private nonprofit, private for-profit, and public. An input-throughput-output framework was used to assess the public-private differences within a wide range of organizational characteristics.