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S J Skinner

Publications and source records attributed to S J Skinner.

At least 37 records · Page 2Linked to original sources
PubMed1992

IGF binding protein-2 gene expression and the location of IGF-I and IGF-II in fetal rat lung.

Binding proteins for the insulin-like growth factors (IGF-BPs) are important modulators of the biological actions of IGF-I and IGF-II. The generation of IGFBPs within developing organs, and their spatial arrangement, may similarly determine IGF action at specific microanatomical sites. In situ hybridization studies with late gestation (days 16, 18 and 20) fetal rat lung using a cDNA probe for IGFBP-2 showed strong gene expression in the fetal lung epithelial structures (alveoli and airways). The sites of IGFBP-2 gene expression were associated with immunoreactive IGF-II at the apical surface of the epithelium. By day 20, there was also some IGFBP-2 gene expression and immunoreactive IGF-II at discrete sites in the mesenchyme. In contrast, immunoreactive IGF-I was found predominantly distributed in a punctate pattern, consistent with its presence in the lumen or walls of small vessels or capillaries, and in a granular, intracellular form in both epithelial and mesenchymal cells. These studies suggest that endogenously generated IGFBP-2 may determine the distribution of IGF-II, principally at the apical surface of lung epithelia. IGF-I does not colocalise with IGF-II peptide or the sites of IGFBP-2 gene expression. We conclude that the spatial distributions of these two related growth factors are separately controlled, to some extent by endogenously generated binding proteins.

Animals↗
PubMed1992

Development of fetal thymocytes in organ culture: effect of corticosteroids.

Corticosteroids affect the development of fetal foregut-derived organs in which epithelial-mesenchymal interactions are associated with the developmental process. The thymus is one such organ and is profoundly sensitive to corticosteroids when mature. In this study corticosterone (CS) effects on fetal thymocyte development were investigated using a fetal thymus organ culture system which allows the growth, differentiation, and function of developing thymocytes to be monitored in vitro. CS inhibited, but did not block growth of fetal thymocytes, although the appearance of mature thymocytes was inhibited, similar to previously reported effects of interleukin 2 (IL2). CS enhanced the proportion of Mac1+, Ia+ and FcR+ cells and maintained high levels of IL2 receptor (IL2R) positive immature cells. Functional cytotoxic cells were detected in CS-treated organ cultures which expressed a Thy 1-, CD8- phenotype, atypical for thymus derived killer cells. While this cytotoxicity may be stimulated by CS, it could simply be due to a relative depletion of the main pool of thymocytes. These cytotoxic cells may have a role in directing apoptotic mechanisms occurring during thymocyte development.

Adrenal Cortex Hormones↗
PubMed1991

Interaction between prostacyclin and cortisol in fetal lung cells: effects on cAMP production.

Glucocorticoids secreted by the fetal adrenal, or administered for therapeutic reasons, stimulate fetal lung maturation in the human and other species. Prostacyclin, produced within the lung may be another agent with maturational effects. In this investigation we have demonstrated that glucocorticoids interact with lung cells and increase their response to a prostacyclin analogue (Iloprost, PGIp). This agent stimulates adenylate cyclase activity in fetal lung fibroblasts, fetal lung epithelial cells and in neonatal vascular smooth muscle cells. The cAMP response to PGIp in fibroblasts and epithelial cells occurred in the range 3nM-1 microM. When fibroblasts were pretreated with cortisol before PGIp, cAMP was increased 2-3 fold (p less than 0.01). There was a similar increase in cAMP after cortisol pretreatment in response to PGIp by fetal lung epithelial cells, but not with smooth muscle cells. The action of cortisol was blocked by an inhibitor of RNA synthesis (Actinomycin D) but not by an inhibitor of DNA synthesis (5-fluorodeoxy-uridine). Additional experiments with cholera and pertussis toxins, and with forskolin suggest that cortisol principally increases the quantity or activity of the adenylate cyclase sub-unit in fetal lung fibroblasts and, in doing so, increases the cAMP response to PGIp.

Adenylate Cyclase Toxin↗
PubMed1991

Transferrin gene expression and transferrin immunolocalization in developing foetal rat lung.

In previous studies we have shown that transferrin (Tf) specifically stimulates dermatan- and chondroitin-sulphate proteoglycan accumulation around lung cells, and in the extracellular matrix of lung tissue, in vitro. The aim of this study was to determine whether the gene for Tf was activated in specific lung cells during development, and whether the protein product showed evidence of association with extracellular matrix. The expression of the gene in developing lung was shown by the hybridization of a Tf cDNA to a 2.4 kb (kilobase) mRNA species in total RNA extracts of foetal lung. The expression of the Tf gene in comparison to a control gene (GAPD, glyceraldehyde phosphate dehydrogenase) was greatest in 19, 20 and 21 day foetal lung, rising from low levels on day 18 and decreasing markedly at term (day 22). Extracts of RNA from primary cultures of mesenchymal fibroblasts and type II epithelial cells were also analysed for Tf mRNA. These experiments indicated that Tf gene expression was predominantly confined to the mesenchymal compartment. The presence of Tf in histological sections of foetal lung was demonstrated by immunohistochemistry and showed a distinct pattern, with intense staining of the alveolar and the capillary basement membranes. The matrix surrounding the mesenchymal fibroblasts was stained in a diffuse network while epithelial cells were unstained. The staining was low from days 12-16 of gestation, increased to a maximum at days 19-20 but decreased markedly toward term. The Tf staining did not co-localize with transferrin receptor, also demonstrated by immunohistochemistry. These results suggest that Tf is not only present at specific sites in the developing lung, but also is synthesized according to a strict developmental schedule of gene expression.

Animals↗
PubMed1990

Adenylate cyclase blockers dissociate PTH-stimulated bone resorption from cAMP production.

It is uncertain whether adenosine 3',5'-cyclic monophosphate (cAMP) or the inositol-calcium pathway mediates the stimulation of bone resorption by parathyroid hormone (PTH). Incubation of bone organ cultures with cAMP analogues and forskolin has not resolved this question because of the cellular inhomogeneity of bone and the consequent presence of adenylate cyclase-linked receptors for both PTH and calcitonin, hormones with opposite effects on bone resorption. We have used two new inhibitors of adenylate cyclase, 9-(tetrahydro-2-furyl)adenine (SQ 22536) and 2',5'-dideoxyadenosine (DDA), to directly reassess the role of cAMP in PTH-stimulated osteolysis. SQ 22536 (0.01-1.0 mM) and DDA (0.01-1.0 mM) completely blocked PTH stimulation of cAMP production measured in the absence of a phosphodiesterase blocker. In the presence of 1 mM 3-isobutyl-1-methylxanthine, half-maximal inhibition of PTH-induced cAMP production occurred with 0.2 mM SQ and 0.1 mM DDA, respectively. These concentrations of SQ and DDA had no effect on PTH-stimulated 45Ca release from calvaria, although both agents inhibited bone resorption when present at concentrations of 1-2 mM. At these levels, SQ and DDA caused equivalent inhibition of 45Ca release stimulated by 1,25-dihydroxyvitamin D3 but did not affect basal 45Ca release or [3H]-phenylalanine incorporation. It is concluded that substantial blockade of PTH-induced cAMP production does not affect this hormone's stimulation of bone resorption, which is therefore likely to be mediated by another intracellular messenger system, possibly calcium. In millimolar concentrations, SQ and DDA appear to be nonspecific blockers of osteoclastic bone resorption.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Leukemia inhibitory factor: a novel bone-active cytokine.

A number of cytokines have been found to be potent regulators of bone resorption and to share the properties originally attributed to osteoclast-activating factor. One such activity, differentiation-inducing factor (DIF, D-factor) from mouse spleen cells, shares a number of biological and biochemical properties with the recently characterized and cloned leukemia inhibitory factor (LIF). We have assessed the effects of recombinant LIF on bone resorption and other parameters in neonatal mouse calvaria. Both recombinant murine and human (h) LIFs stimulated 45Ca release from prelabeled calvaria in a dose-dependent manner. The increase in bone resorption was associated with an increase in the number of osteoclasts per mm2 bone. The osteolytic effect of hLIF were blocked by 10(-7) M indomethacin. hLIF also stimulated incorporation of [3H] thymidine into calvaria, but the dose-response relationship was distinct from that for bone resorption, and this effect was not blocked by indomethacin. Similarly, hLIF increased [3H]phenylalanine incorporation into calvaria, and this was also not inhibited by indomethacin. It is concluded that LIF stimulates bone resorption by a mechanism involving prostaglandin production, but that a distinct mechanism is responsible for its stimulation of DNA and protein synthesis. The primary structure of LIF differs from that of other fully characterized, bone-active cytokines, and it, thus, represents a novel factor which may be involved in the normal regulation of bone cell function.

Animals↗
PubMed1990

Chondrons from articular cartilage (II): Analysis of the glycosaminoglycans in the cellular microenvironment of isolated canine chondrons.

A chondron rich preparation was isolated from mature canine tibial cartilage using low-speed homogenization techniques. Proteoglycans were extracted from this preparation by exhaustive treatment with 4M guanidine-HCl. A significant proportion of the total proteoglycan, measured as uronic acid, was resistant to extraction and represented 27.9% in intact cartilage chips and 18.6% in the chondron fraction. Histochemical examination of chondrons confirmed that extraction resistant proteoglycans remained within the capsule of the chondron after 4M guanidine-HCl treatment. Electrophoretic analysis of the glycosaminoglycans extracted from intact cartilage chips and the chondron fraction showed approximately equivalent amounts of chondroitin sulphate (79.3%), keratan sulphate (16.3%) and hyaluronic acid (4.3%) present. In contrast, the extraction resistant residue in the chondron fraction was significantly enriched for hyaluronic acid (10.5%, p less than 0.05) but was depleted of chondroitin sulphate (70.9%, p less than 0.05). The major chondroitin sulphate isomer in the resistant fraction was chondroitin 6-sulphate while in the soluble fraction, the quantities of the two isomers were approximately equivalent. Comparison with previously published data suggests a role for minor collagens in the retention of proteoglycans in the cellular microenvironment.

Animals↗
PubMed1989

Transferrin stimulates proteoglycan accumulation by fetal lung cells in culture.

The role of transferrin in growth and the formation of extracellular matrix was investigated by comparing its effects on proteoglycan metabolism and cell proliferation in primary cultures of fetal rat lung fibroblasts and Type II epithelial cells. Transferrin specifically stimulated the accumulation of dermatan/chondroitin sulfate proteoglycans associated with the cells and matrix in a dose-dependent manner (0-200 micrograms/ml, r = .850 in fibroblasts and r = .810 in Type II cells). This effect was not due to increased synthesis since there was a corresponding decrease in proteoglycans and their degradation products released into the medium. The effect is probably mediated via an action on the proteoglycan core protein, since there was no effect of transferrin on enzyme activity promoting glycosaminoglycan synthesis on the synthetic initiator beta-D-xyloside. The effect of transferrin on proteoglycan distribution was not a secondary effect caused by changes in collagen synthesis and was not linked to cell proliferation or the concentration of Fe3+ ions in the culture medium.

Animals↗
PubMed1989

Effects of corticosteroids, prostaglandin E2, and beta-agonists on adenylate cyclase activity in fetal rat lung fibroblasts and type II epithelial cells.

The effect of glucocorticoids on the response of adenylate cyclase in fetal rat lung fibroblast and Type II epithelial cell cultures to beta-agonists and prostaglandin E2 (PGE2) was investigated. There was significant stimulation of cyclic AMP synthesis by adrenalin in both fibroblasts and Type II cells, which was potentiated in a dose-dependent manner by cortisol. Stimulation of adenylate cyclase by PGE2 (10-1000 nM) was demonstrated in fibroblasts but not in Type II cells. The response to PGE2 was stimulated by pretreatment with cortisol only in fibroblasts (p less than .01), and no latent response to PGE2 was evident in Type II cells after cortisol treatment. These experiments suggest that both cell types isolated from late gestation fetal lung contain active beta-agonist and glucocorticoid receptors that synergize in raising intracellular cyclic AMP, which has multiple effects, including surfactant secretion from Type II cells. Since the adenylate cyclase response to PGE2 and its enhancement by glucocorticoids occurred only in fibroblasts, it is concluded that the reported effects of PGE2 on surfactant release are not mediated via raised intracellular cyclic AMP in Type II cells.

Adenylyl Cyclases↗
PubMed1987

Association between season of first detection of breast cancer and disease progression.

The season of recurrence of tumour was investigated by follow-up of 1324 patients with breast cancer and compared with the season of initial tumour detection. Unlike primary tumours, where an increased incidence of detection has previously been observed in late spring and early summer, there was no significant seasonal variation in the time of recurrence. However, women with oestrogen receptor positive or progesterone receptor negative primary tumours recurred significantly more frequently in the same season that their primary cancer was initially detected. Overall there was an increased frequency of recurrence one year from diagnosis. Women less than age 50 who initially found their tumour in winter or autumn had a significantly shorter disease-free interval before recurrence than those first detecting their tumour in summer or spring. This relationship was independent of nodal status and tumour size. Tumours initially detected in winter or autumn thus appeared to follow a more aggressive growth profile. This study indicates that the season of first detection of a breast cancer relates significantly to aspects of the future biologic behaviour of the tumour.

Breast Neoplasms↗
PubMed1987

Progressive mental regression in siblings with Morquio disease type B (mucopolysaccharidosis IV B).

A brother and sister with clinical and radiological features of Morquio disease, but with atypical mental regression, are described. Leucocyte and fibroblast beta-galactosidase activity was deficient in the siblings, while N-acetylgalactosamine 6-sulphate sulphatase and neuraminidase were normal. Study of the residual fibroblast beta-galactosidase activity towards 4-methylumbelliferyl and p-nitrophenyl beta-D-galactosides indicated that the mutation resembles that in typical Morquio B disease (increased Km and similar pH maximum) rather than that in GM1-gangliosidosis. The patients have therefore been classified as having Morquio B disease with atypical mental regression rather than GM1-gangliosidosis variants with particularly severe bony abnormalities. The mutation was, however, distinct from that in Morquio B disease since residual activity towards the alternative artificial substrate 4-methylumbelliferyl-beta-D-fucoside was increased. The patients represent further examples of the heterogeneity that can result from mutation at the beta-galactosidase locus.

Bone Diseases, Developmental↗
PubMed1987

Characterization of proteoglycans synthesized by fetal rat lung type II pneumonocytes in vitro and the effects of cortisol.

The synthesis of proteoglycans by primary cultures of 19-day gestation fetal rat lung Type II pneumonocytes was studied. The cells were grown in the presence of [3H]-glucosamine and/or [35S]-Na2SO4 and the radioactive label incorporated into proteoglycans was analyzed. Proteoglycans of high molecular weight (approximately 200 Kd) were isolated by gel permeation chromatography and contained both [3H] and [35S]. The glycosaminoglycan composition of the proteoglycans was determined by electrophoresis and autoradiography. The medium contained 65-80% of the labeled proteoglycans and was enriched for hyaluronate, with lesser amounts of the sulfated glycosaminoglycans (dermatan sulfate greater than heparan sulfate greater than chondroitin sulfate). The cell layers retained 20-35% of the labeled proteoglycans and was enriched for heparan sulfate, with lesser amounts of chondroitan sulfate greater than dermatan sulfate greater than hyaluronate. The synthesis of proteoglycans was time-dependent and was stimulated by increasing concentrations of fetal bovine serum. Cortisol inhibited proteoglycan synthesis, apparently by decreasing the availability of proteoglycan core-protein.

Animals↗
PubMed1985

Partial purification and characterisation of two compounds from amniotic fluid which inhibit phospholipase activity in human endometrial cells.

Two inhibitors of PGF synthesis in human endometrial cells were found in amniotic fluid from term non-labouring patients. Both inhibitors at 10(-9)M reduced the amount of arachidonic acid released from the cells but had no effect on PGF synthesis stimulated by arachidonic acid. The molecular weights were 150-165,000 and 70-80,000 daltons as estimated from gel filtration in two systems. Both compounds precipitated with ammonium sulfate, appeared thermostable and lost activity with trypsin digestion. Both inhibited phospholipase activity and had identical retention times with HPLC. We conclude that the compounds are novel endogenous proteins which inhibit endometrial cell phospholipase.

Amniotic Fluid↗
PubMed1985

Seasonal variation in breast cancer detection: correlation with tumour progesterone receptor status.

A significant circannual variation of the month in which patients detect the first sign or symptom of tumour has been defined in 1413 patients with breast cancer. The months of highest detection were in the late spring-early summer, and lowest detection was in late autumn-early winter. Analysis of subgroups indicates that this cyclic trend was most significant in younger women with small or moderate-sized tumours containing steroid hormone receptors, particularly progesterone receptors. It seems likely that this variation is related to the effect of cyclic hormonal changes on tumour growth, possibly mediated through the pineal.

Adult↗
PubMed1984

The separation of collagen alpha-chains by reversed-phase high-performance liquid chromatography. Comparison of column alkyl stationary phases and temperature effects.

Procedures for the separation of alpha 1(I), alpha 2(I), alpha 1(II) and alpha 1 (III) chains of human collagen by reversed-phase high-performance liquid chromatography are described. The influence of several different chromatographic parameters (stationary phase, mobile phase and temperature) has been examined and procedures to optimise resolution presented. These reversed-phase high-performance liquid chromatographic conditions also permit the separation of collagen alpha 1(I), alpha 2(I), alpha 1(II) and alpha 1(III) monomers from their corresponding dimeric beta- and gamma-components.

Amino Acids↗
PubMed1984

Estrogen receptor status, adrenal androgens and 7 alpha-hydroxydehydroepiandrosterone in breast cancer patients.

Plasma concentrations of dehydroepiandrosterone (DHA), DHA-sulphate (DHAS) and 7 alpha hydroxy-DHA (7 alpha OHDHA) were measured and compared with tumor estrogen receptor (ER) status in 33 postmenopausal patients with breast cancer. Although the plasma concentrations of DHA, DHAS and 7 alpha OHDHA were not different between the ER-positive (ER+) and ER-negative (ER-) patient groups, the ratios of 7 alpha OHDHA/DHAS and of DHA/DHAS were significantly higher (P less than 0.001 and P less than 0.001 respectively) in the ER- group. Nine women (normal or with benign breast disease) of similar age and menopausal status had values for plasma 7 alpha OHDHA/DHAS and DHA/DHAS between those of ER+ and ER- patient groups. The measurement of these steroid ratios in the plasma of breast cancer patients thus provides an indirect estimate of ER status. Since DHA and 7 alpha OHDHA are major metabolites of precursor DHAS in mammary tumor tissues, changes in their relative quantities in plasma may reflect the influence of receptor-mediated events on mammary steroid metabolism. Alternatively, the relative increase in tumor metabolism of androgens inferred from high 7 alpha OHDHA/DHAS and DHA/DHAS ratios in the ER- group may disrupt the hormonal microenvironment of the estrogen receptor. These events may, in turn, predispose toward ER status and a poor response to endocrine therapy.

Age Factors↗