PubMed Health⌕ Search

Biomedical subjects

E M Düker

Publications and source records attributed to E M Düker.

7 recordsLinked to original sources
PubMed1991

Effects of extracts from Cimicifuga racemosa on gonadotropin release in menopausal women and ovariectomized rats.

Remifemin is an ethanolic extract of the rhizome of Cimicifuga racemosa (C.r.) and is used to relieve climacteric hot flushes. In the present study the effects of this preparation on LH and FSH secretion of menopausal women were investigated. After an 8 weeks treatment, LH but not FSH levels were significantly reduced in patients receiving the Cimicifuga extract. To further characterize the endocrinologically active principles of this plant extract, a lipophilic extract of C.r. was prepared and subjected to Sephadex chromatography. Fractions obtained were tested for their ability to reduce LH secretion in ovariectomized (ovx) rats and to compete in vitro with 17 beta-estradiol for estrogen receptor binding sites. Three types of endocrinologically active compounds were obtained: (1) Constituents which were not ligands for the estrogen receptor but suppress LH release after chronic treatment, (2) constituents binding to the estrogen receptor and also suppressing LH release, and (3) compounds which are ligands for the estrogen receptor but without an effect of LH release. It is concluded that the LH suppressive effect of C.r. extracts observed in menopausal women and ovx rats is caused by at least three different synergistically acting compounds.

Animals↗
PubMed1987

Stress-induced changes in cholecystokinin and substance P concentrations in discrete regions of the rat hypothalamus.

The effects of acute stress exposure upon cholecystokinin (CCK) and substance P (SP) concentrations in discrete hypothalamic regions of the adult male rat brain were studied. Animals were exposed to foot shock stress for periods of 2, 4, 10, 30 or 60 min duration; immediately afterwards they were decapitated; brains were frozen and subsequently microdissected. CCK and SP concentrations were assayed by a specific RIA, as were serum levels of ACTH, corticosterone, PRL, GH, LH and testosterone. Stress had no effect upon SP concentrations in the anterior or posterior parts of the arcuate nucleus (ARC), but led to elevated CCK levels in the posterior ARC following 60 min of exposure. In both the ventromedial and dorsomedial hypothalamic areas, stress induced depletions of both neuropeptides. In the anterior (but not the posterior) portions of the lateral hypothalamic area, CCK and SP concentrations were reduced by stress exposure. These studies demonstrate that discrete hypothalamic CCK and SP neuronal systems are responsive to stress. This suggests that endogenous hypothalamic CCK and SP participate, along with other neurotransmitters/neuromodulators, in the integrated hypothalamic stress response, and mediate stress-neuroendocrine interactions.

Animals↗
PubMed1986

Intraovarian secretion of catecholamines, oxytocin, beta-endorphin, and gamma-amino-butyric-acid in freely moving rats: development of a push-pull tubing method.

We have developed and validated a push-pull technique that allows focal perfusion of the ovary in unanesthetized freely moving rats. We have used this method to investigate the intraovarian secretion of catecholamines (dopamine, norepinephrine, epinephrine), oxytocin, beta-endorphin and gamma-amino-butyric acid (GABA) during the estrous cycle. Cycling animals were implanted with ovarian push-pull catheters and jugular vein catheters under ether anaesthesia on proestrus, estrus and diestrous Day 2. This procedure did not disrupt normal preovulatory release of prolactin and luteinizing hormone (LH). Thus, perfusion of the ovary and simultaneous monitoring of hormone levels in systemic blood in freely moving rats allow correlation of the temporal relationship of ovarian events with cyclic gonadotropin secretion. The results clearly indicate that a rise in ovarian norepinephrine occurs concomitant with the preovulatory surge in prolactin and LH. Ovarian beta-endorphin concentrations exhibit cyclic changes, whereas GABA release rates remain stable throughout the cycle. Oxytocin is secreted by ovarian tissue, and the secretion rate appears to be inversely related to prolactin. In view of the proposed involvement of ovarian nerves and particularly catecholamines in the process of follicular maturation and ovulation, our findings suggest a preovulatory activation of ovarian noradrenergic sympathetic neurons.

Animals↗
PubMed1985

Adrenal release of catecholamines and Met-enkephalin before and after stress as measured by a novel in vivo dialysis method in the rat.

A dialysis tubing was implanted in the adrenal gland of rats. Adrenomedullary secretion products were dialysed into Ringer solution in the awake animal. Catecholamines (CAs) and methionine-enkephalin (Met-Enk) were measurable under resting conditions. Epinephrine, norepinephrine and Met-Enk-like immunoreactive material increased following application of an immobilization stress for 5 min. The results demonstrate that adrenomedullary CAs and peptides are coreleased. They also demonstrate that Met-Enk-like immunoreactive material is released under stress.

Adrenal Medulla↗
PubMed1984

Light-microscopic visualization of F and type 1 pili.

Methods for the direct visualization of F and type 1 pili of Escherichia coli in the light microscope are described. The method for visualizing F pili is based on the specific adsorption of fluorescent dye-labelled RNA phages to F pili. The best results were obtained with MS2 phages labelled with rhodamine B. Semi-quantitative determination of the amount of F pili is possible. Type 1 pili can be visualized rapidly and specifically by indirect immunofluorescence. Other structures on the cell surface are neither detected by, nor interfere with these assays. By using different fluorescent dyes the two methods can be combined and both F and type 1 pili can be determined in the same sample.

Adsorption↗
PubMed1984

F and type 1 piliation of Escherichia coli.

F and type 1 piliation of various Escherichia coli K12 Hfr and F+ strains was re-examined by using a new visualization assay. In anaerobic cultures in rich media, bacteria were well F piliated throughout all growth phases. In aerobic cultures in rich media, F piliation reached a maximum in the mid-exponential phase. The yield of pili was up to 15 mg 1(-1). In aerated cultures, F pili disappeared in the late exponential phase. In rich media F pili were on average 10-20 micron long; in synthetic media they were an order of magnitude shorter, and less numerous. Addition of metabolic poisons (NaCN, NaN3, Na3AsO4, phenylethyl alcohol) and starving the bacteria caused rapid disappearance of F pili under aerobic conditions, but had no influence on F piliation under anaerobic conditions. Type 1 piliation was not influenced by these drugs or by an alteration of growth conditions.

Arsenates↗