Biomedical subjects

S Schuett

Publications and source records attributed to S Schuett.

4 recordsLinked to original sources

PubMed2001

Pairing-induced changes of orientation maps in cat visual cortex.

We have studied the precise temporal requirements for plasticity of orientation preference maps in kitten visual cortex. Pairing a brief visual stimulus with electrical stimulation in the cortex, we found that the relative timing determines the direction of plasticity: a shift in orientation preference toward the paired orientation occurs if the cortex is activated first visually and then electrically; the cortical response to the paired orientation is diminished if the sequence of visual and electrical activation is reversed. We furthermore show that pinwheel centers are less affected by the pairing than the pinwheel surround. Thus, plasticity is not uniformly distributed across the cortex, and, most importantly, the same spike time-dependent learning rules that have been found in single-cell in vitro studies are also valid on the level of cortical maps.

Animals↗

PubMed2001

Endothelin-1 synthesis and endothelin B receptor expression in human coronary artery smooth muscle cells and monocyte-derived macrophages is up-regulated by low density lipoproteins.

Endothelin-1 (ET-1) is a potent vasoconstrictive peptide exerting its effects predominantly by paracrine and autocrine mechanisms. ET-1 acts as a mitogen and co-mitogen on vascular smooth muscle cells, and accumulating evidence suggests that ET-1 is involved in the pathogenesis of atherosclerosis. Deposition of low density lipoproteins (LDL) in the vessel wall is known to play a crucial role in the development of atherosclerotic lesions. In the present study, we have investigated the effect of native LDL (nLDL) and oxidatively modified LDL (oxLDL) on ET-1 synthesis and endothelin receptor expression in cultured human coronary artery smooth muscle cells and human monocyte-derived macrophages. Native LDL and oxLDL induced a significant stimulation of ET-1 release and ET-1 mRNA expression in human coronary artery smooth muscle cells and monocyte-derived macrophages. Antibodies against the scavenger receptor CD36 significantly reduced the oxLDL-induced stimulation of ET-1 synthesis. The antioxidants trolox and probucol did not significantly inhibit the LDL-induced rise of ET-1 release. Endothelin B receptor expression was up-regulated in both cell types after incubation with nLDL and oxLDL. In coronary smooth muscle cells, endothelin A receptor expression was slightly increased by LDL, whereas endothelin A receptor was not detectable in monocyte-derived macrophages. Coronary artery smooth muscle cells secreted a more than 150-fold higher amount of immunoreactive ET-1 into the cell culture medium than monocyte-derived macrophages. In summary, the present data, demonstrating a LDL-induced up-regulation of the endothelin system in coronary smooth muscle cells and in monocyte-derived macrophages, provide further support for a pathophysiological role of endothelin in coronary atherosclerosis and suggest that ET-1 might be involved in mediating the atherogenic effects of LDL.

Cells, Cultured↗

PubMed2000

Hepatocyte growth factor is upregulated by low-density lipoproteins and inhibits endothelin-1 release.

Low-density lipoproteins (LDL) are known to cause endothelial injury and to promote the development of atherosclerotic lesions. This study demonstrates a significant concentration-dependent stimulatory effect of LDL on hepatocyte growth factor (HGF) synthesis (maximum release: 423 +/- 16% of control) and HGF receptor mRNA expression in cultured human coronary artery endothelial cells (HCAEC). HGF is a potent mitogen for endothelial cells but does not affect smooth muscle cell proliferation. In contrast, endothelin-1 (ET-1) acts as a mitogen on vascular smooth muscle cells and seems to be upregulated in coronary atherosclerosis. In this study, the basal ET-1 synthesis in HCAEC was concentration-dependently reduced by HGF (minimum: 54 +/- 3% of control). This inhibitory effect seems to be mediated via the tyrosine kinase activity of the HGF receptor c-met, since it was antagonized by the tyrosine kinase inhibitor lavendustin A. In addition, HGF also significantly reduced the LDL-stimulated ET-1 release. The LDL-induced upregulation of HGF synthesis in HCAEC and the inhibitory effect of HGF on ET-1 synthesis suggest a protective role of HGF in coronary atherosclerosis.

Cells, Cultured↗

PubMed1996

Loneliness and social support in infertile couples.

OBJECTIVE: To determine differences between infertile wives' and husbands' levels of loneliness and perception of social support and to determine if there is a relationship between loneliness and social support. DESIGN: Comparative descriptive. SETTING: University infertility clinic and RESOLVE, an infertility support group. PARTICIPANTS: Convenience sample of 62 couples diagnosed as experiencing either primary or secondary infertility. OUTCOME MEASURES: Loneliness was measured using the Revised UCLA Loneliness Scale; social support was measured using the Interpersonal Relationship Inventory with subscales of Social Support, Reciprocity, and Conflict. RESULTS: Wives were significantly more lonely than husbands (t = 2.053, p = 0.04). There was no significant group difference on the social support total score or three subscale scores. Loneliness was inversely related to social support and reciprocity both for wives (r = -0.62, p = 0.001, and r = -0.50, p = 0.002, respectively) and husbands (r = -0.74, p = 0.001, and r = -0.56, p = 0.001, respectively); loneliness correlated with conflict for wives only (r = 0.48, p = 0.007). CONCLUSIONS: Although wives and husbands differed in loneliness, they were similar in perceived social support. Greater social support and reciprocity lessened feelings of loneliness for both groups. Wives who perceived increased conflict in their social relationships were more lonely.

Adult↗