Scleral fibroblasts, perichondrial cells of the scleral layer of the 12-day chick embryo, always manifest a fibroblastic morphology in monolayer culture. In soft-agar culture, these cells produce two types of colonies. One type of colony, F-type, consists of adherent fibroblastic cells, and the other, C-type, is composed of scattered round chondrocytic cells. Cells of the C-type colony are surrounded by a halo of extracellular matrix, positive with Alcian blue and with an antibody to cartilage-specific proteoglycan. When a single fibroblast clone in monolayer, derived from a single scleral fibroblast, is subcultured into soft agar, the cells give rise to both C-type and F-type colonies. Further, it was found that cells constituting F-type colonies eventually separate and become spherical, and the F-type colony converts to a C-type colony (C-type conversion). In regard to the C-type convertibility, the primary fibroblast clones were divided into four categories, early time differentiating, middle-time differentiating, late-time differentiating and nondifferentiating. This suggests that the scleral perichondrial layer of the 12-day chick embryo is composed of a variety of cells with different chondrogenic potentialities maintained in each individual cell.

Agar↗

PubMedDate not supplied

Geometric response to nerve growth factor is preserved in aged rat sensory neurons: a single-neuron culture study.

We previously established a single-neuron culture system to analyze the primary effects of neurotrophic factors and reported that NGF promoted neurite extension in young adult (4- to 6-month-old) rat dorsal root ganglion (DRG) neurons by promoting neurite arborization. In this study, we demonstrated that the effects of NGF on neurite regeneration in DRG neurons was well preserved in aged rats (20- to 24-month-old and 33-month-old). NGF did not increase the percent process-bearing neurons in aged rats, which indicated that neuronal survival was not promoted by NGF, but it significantly enhanced the number of branching points, total neurite length, and soma size in aged neurons. These effects of NGF on neurite geometry tended to be reduced to some extent in aged neurons and the initiation of neurite-outgrowth in aged neurons was also delayed as compared with young adult neurons. NGF-responsive subpopulation of neurons, found in the entire range of neuronal size, were preserved in aged rats. These findings indicate that NGF could play an important role in regeneration of injured DRG neurons of aged animals.

Aging↗

PubMedDate not supplied

New genetic approaches to craniofacial growth and malformation in the mouse.

New genetic tools that have been developed in the mouse for the study of genetic variation and molecular biology can be applied to the study of craniofacial growth and malformation. D.W. Bailey (Journal of Heredity, 76:107-114, 1985, 77:17-25, 1986) has used congenic and recombinant inbred strains to identify a large number of genes that result in growth variation in local regions of the mandible. The function of "morphogenes" have not been characterized, but they may act as switches that regulate already recognized structural genes. We have studied the cartilage matrix deficiency (cmd/cmd) mutant mouse and found that their chondrocytes fail to synthesize the cartilage-specific proteoglycan at both protein and mRNA levels. In vitro experiments demonstrate biochemical feedback control in the formation of the cartilage extracellular matrix. Abnormalities of cartilage matrix result in facial clefts and in dental malocclusion in mice. A recombinant plasmid containing the type II collagen promoter and enhancer fused to a reporter gene, chloramphenicol acetyl transferase, has been used to produce transgenic mice. These mice reveal that the type II collagen enhancer controls the high level of tissue-specific expression of the gene. The transgenic mice provide a potential test system for study of development and teratogenesis at the gene level.

Animals↗

PubMedDate not supplied

Modulation of cytokine function by heparan sulfate proteoglycans: sophisticated models for the regulation of cellular responses to cytokines.

Cytokines are diffusible, soluble factors with pleiotropic actions. The ability of some cytokines to blind to and be immobilized by heparan sulfate proteoglycan (HS-PG) on either the surface of cells or within the extracellular matrix accentuates their action by 1) promoting the accumulation of cytokines at high concentrations in the appropriate location to encounter their target cells; 2) activating cytokines by inducing conformational changes in the bound cytokine; 3) promoting conformation-dependent association or polymerization of cytokines and their cell-surface receptors and facilitating the assembly of the appropriate molecular complex to initiate signal transduction; and 4) protecting cytokines from both chemical and physiological degradation. Furthermore, many interactions between HS-PG and cytokines are highly specific. Thus, variations in the HS-PG, core protein, or carbohydrate sequences that are seen at different sites or that occur with inflammation will determine which cytokines bind to a particular HS-PG, providing multiple options for cytokine binding and regulation. HS-PG therefore plays a pivotal role in regulating the function of the large number of heparin-binding cytokines. The involvement of HS-PG in promoting paracrine, autocrine, juxtacrine, and matricrine functions provides a powerful and sophisticated model for regulating cytokine-mediated cellular interactions. These functions of HS-PG have direct relevance for the control of cell growth as well as for the pathogenesis of leukocyte trafficking and inflammation, cell infiltration, and tumor metastasis. Therapies aimed at modulating HS-PG/cytokine binding may provide powerful tools for inhibiting unwanted cytokine effects in several disease processes.

Cytokines↗