Differentiation of photoreceptors and horizontal cells in the embryonic mouse retina: an electron microscopic, serial section analysis.

The early differentiation of photoreceptors and horizontal cells in the mouse retina has been studied with serial thin sections and reconstructions in embryos on the fifteenth and seventeenth days of gestation (E15 and E17). The following developmental sequences have been inferred. At E15 photoreceptors develop from ventricular cells when a long vitreal process fails to develop following mitosis, and the end of the ventricular process forms a bulbous enlargement (the future inner segment) which contains a pair of centrioles and a cilium and extends into the optic ventricle. This future inner segment is considerably larger at E17, but otherwise the photoreceptors resemble those seen at E15. At E15 horizontal cells develop from ventricular cells when a long vitreal process fails to develop following mitosis, and the end of the ventricular process detaches from the junctional complex at the ventricular surface. By E17 future horizontal cells are located in the middle of the ventricular layer (neuroblastic layer) and have developed from bipolar shaped cells into cells with multiple branching processes, predominantly radially arranged but rarely with a more tangential orientation. These relatively advanced cells at E17 resemble closely the earliest stage of horizontal cell formation described previously in silver studies by Cajal. A scheme is proposed which explains the initial differentiation of several of the major cell types in the retina in terms of two key features: whether or not the call remains attached to the junctional complex and whether or not a vitreal process grows into the ganglion cell layer. By independent variations in these two features, four classes of cells are produced that, by virtue of their differing environments, differentiate into four cell types: ganglion (and amacrine) cells, horizontal cells, photoreceptors, and Müller cells.     

Differences in amphetamine and morphine sensitivity in lateralized and non-lateralized rats: locomotor activity and drug self-administration

Morphine and d-amphetamine were tested for their effects on locomotor activity and for their propensities to be intravenously self-administered in rats that had been screened for their tendencies to rotate (turn in circles) spontaneously at night; noctural rotation was used as a behavioral index of asymmetry in the dopaminergic nigrostriatal system. Lateralized (rotating) rats were more sensitive to the locomotor stimulant effects of d-amphetamine than non-lateralized (non-rotating) rats. The stimulant effects of low doses of morphine were also greater in lateralized rats, whereas the depressant effects of high doses of morphine were greater in non-lateralized rats. Lateralized rats self-administered more d-amphetamine than non-lateralized rats whereas non-lateralized rats self-administered more morphine than lateralized rats. The data indicate that the degree of lateralization in some brain pathways is a source of interindividual variation in drug sensitivity--this may in part be responsible for the individual tendencies of humans to selectively abuse particular types of drugs.     

Creating a novel structure for nursing research in a cooperative clinical trials group: the Children's Oncology Group experience

OBJECTIVE: To describe a novel structure designed to integrate nursing research into the Children's Oncology Group (COG). DATA SOURCES: Review articles, reports, and newsleters. CONCLUSION: A new structure using nurse researcher-advanced practice nurse dyads has succesfully integrated nurse researchers into COG scientific activity, as evidenced by the development of concept proposals, companion protocols, nursing objectives in therapeutic trials, and nurse-led publications. IMPLICATIONS FOR NURSING PRACTICE: This provides a promising method for integrating nurse researchers and increasing multidisciplinary research collaboration in cooperative oncology group.     

A review of complementary mechanisms which protect the developing marsupial pouch young

Marsupials are born without a functioning adaptive immune system, into a non-sterile environment where they continue to develop. This review examines the extent of exposure of pouch young to microorganisms and describes the protective mechanisms that are complementary to adaptive immunity in the developing young. Complementary protective mechanisms include the role of the innate immune system and maternal protection strategies, such as immune compounds in milk, prenatal transfer of immunoglobulins, antimicrobial compounds secreted in the pouch, and chemical or mechanical cleaning of the pouch and pouch young.     

Capture of flowing endothelial cells using surface-immobilized anti-kinase insert domain receptor antibody

In humans, self-endothelialization of synthetic grafts is severely limited, but a recent interesting idea is to attract endothelial progenitor cells (EPCs) from peripheral blood onto grafts via antibodies directed at proposed EPC markers. Results with anti-CD34 antibodies have shown some promise, but it is unclear whether CD34 is the best marker for cells with re-endothelializing potential. Much evidence points to kinase insert domain receptor (KDR) as an important indicator of endothelial potential if not a definitive marker. Because KDR is not an adhesion molecule (like CD34), we first demonstrated the ability to use adsorbed and protein G-oriented antibody to this receptor to capture flowing cells onto a solid surface. Using endothelial cells and smooth muscle cells, we show in a model system under low shear rates the ability to selectively capture cells by this receptor. Furthermore, our results indicate that concomitant flow of cells lacking the receptor does not affect the efficiency of capture of KDR(+) cells but that orienting the antibody significantly increases the efficiency of capture.     

Structural and cellular characterization of electrospun recombinant human tropoelastin biomaterials

An off-the-shelf vascular graft biomaterial for vascular bypass surgeries is an unmet clinical need. The vascular biomaterial must support cell growth, be non-thrombogenic, minimize intimal hyperplasia, match the structural properties of native vessels, and allow for regeneration of arterial tissue. Electrospun recombinant human tropoelastin (rTE) as a medial component of a vascular graft scaffold was investigated in this study by evaluating its structural properties, as well as its ability to support primary smooth muscle cell adhesion and growth. rTE solutions of 9, 15, and 20?wt% were electrospun into sheets with average fiber diameters of 167?±?32, 522?±?67, and 735?±?270?nm, and average pore sizes of 0.4?±?0.1, 5.8?±?4.3, and 4.9?±?2.4?μm, respectively. Electrospun rTE fibers were cross-linked with disuccinimidyl suberate to produce an insoluble fibrous polymeric recombinant tropoelastin (prTE) biomaterial. Smooth muscle cells attached via integrin binding to the rTE coatings and proliferated on prTE biomaterials at a comparable rate to growth on prTE coated glass, glass alone, and tissue culture plastic. Electrospun tropoelastin demonstrated the cell compatibility and design flexibility required of a graft biomaterial for vascular applications.