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Connexin43 (Cx43) is the most abundantly expressed member of the connexin (gap junction protein) family and the only one so far identified in mouse Leydig cell gap junctions. Mice lacking Cx43 were used to investigate its role in testicular androgen production and regulation. Testes from term fetuses were grafted under the kidney capsules of castrated adult males. After 3 weeks, serum from host mice was analyzed for androgens. In order to test their response to stimulation, the grafted testes were incubatedin vitrowith varying concentrations of LH and their androgen end products analyzed. Incubation with radiolabeled progesterone was followed by high performance liquid chromatography to quantify the androgen-intermediate metabolites. Radiolabeled testosterone in the presence of NADPH was used to determine the activity of testosterone-metabolizing enzymes 17β-hydroxysteroid dehydrogenase (17βHSD), 5α-reductase (5αR), and 3α-hydroxysteroid dehydrogenase (3α HSD). Serum androgen levels did not differ between hosts carrying wild-type versus null mutant grafts although Cx43-deficient testes had more 17βHSD and 5αR activity than wild-type controls. Furthermore, the genotype of grafted testes did not influence LH-stimulated androgen productionin vitro. These results indicate that the steroidogenic function of Leydig cells is not compromised by the absence of Cx43, perhaps because other gap junction proteins are present. Dye transfer experiments demonstrated that Cx43-deficient Leydig cells retain intercellular coupling, indicating that Cx43 is not the only protein contributing to their gap junctions. Thus, despite their prominence in Leydig cells, Cx43 gap junctions are not essential for androgen production.

Bone marrow is the major site of hematopoiesis in the adult mammal. Bone marrow contains a highly organized microenvironment for the support of hematopoietic stem and progenitor cells, including the production of growth factors. Bone marrow cells also produce negative regulatory factors which may regulate hematopoiesis and inflammatory responses. In this paper we describe Reptimed, a unique bone marrow-derived factor with inhibitory activity for myelopoiesis and in vitro growth of myeloid cell lines. Reptimed was partially purified from bone marrow supernatants using a combination of solid-phase extraction and size exclusion chromatography. Reptimed is < 1000 Da MW and is water soluble. Reptimed inhibited growth of granulocyte-macrophage and macrophage colonies as well as proliferation of several myeloid leukemia cell lines. Reptimed may be part of a hemoregulatory circuit.

Human adipose stromal cells provide an excellent model for studying a variety of metabolic processes in an in vitro system These are normal cells derived from subcutaneous or omental adipose tissue. Under specific culture condition, they will differentiate without replication into cells resembling mature adipocytes or will replicate, become confluent, and grow in subculture. The initial observation that the stromal vascular fraction of human omental adipose tissue contained a fibroblast-like cell that was a possible adipocyte precursor was made by Poznanski et al (1). Subsequent studies demonstrated enzymological and morphological properties that developed during differentiation (2-4). The primary interest has focused on the conditions required to stimulate these cells to differentiate into adipocytes, which can accumulate lipid and possess the enzymes involved in lipogenesis, including glycerol-3-phosphate dehydrogenase (GPDH) and lipoprotein lipase (LPL).

More than thirty monohydroxy sterols were detected in the marine sponge Petrosia ficiformis , ranging from the ubiquitous 24-norcholesta-5, 22-dien-3β-o1 to the C30 sterol, 24-propylidenecholesterol. A new minor sterol was isolated and shown by spectral analysis and comparison with a synthetic sample to be (24R)-24,26-dimethy1cho1esta-5,26-dien-3β-o1 [26(29)-dehydroap1ysterol] ( 12 ).