PubMed Health⌕ Search

Biomedical subjects

A Ecker

Publications and source records attributed to A Ecker.

At least 19 recordsLinked to original sources
PubMed1997

The demonstration of progesterone, but not of estrogen, receptors in the developing human placenta.

Since presence of steroid receptors in the human placenta has been the subject of dispute, we have investigated the existence of estrogen (ER) and progesterone (PR) receptors in trophoblasts across gestational age by a variety of different techniques. Fresh human placental tissue of trimesters 1 to 3 was paraffin-embedded or snap-frozen (-80 degrees C) and sliced (5 microns). Other tissue fragments from identical placentae were dispersed and incubated in monolayer cultures for up to 5 days. Immunocytochemistry (ICC) was performed for ER and PR in both trophoblast cells in culture and in whole tissue slices, using the sandwich antibody technique with subsequent horse-radish peroxidase reaction for colorization. In addition, long-term perifusion studies were conducted with explants of term placentae, using perifusion medium with estradiol (E, 2 ng/ml) and/or progesterone (P, 200 ng/ml). Perifused explants were then subjected to further ICC staining. Furthermore, RT-PCR for both ER and PR mRNA was performed for detection of the gene products in placentae of different gestational ages. Lastly, binding studies with iodine or tritium-labeled E and P were conducted on cytosol fractions. In placental sections and cultured trophoblasts, PR was clearly demonstrable in all placentae across different gestational ages. Abundant PR signal was found adjacent to the nuclei, and additionally in the dendrite-like pseudopods of syncytiotrophoblast cells. In contrast, no such staining signal was detected for the ER; this finding applied under all conditions investigated and at all gestational ages. Again, no staining for ER by ICC was detected in any tissue after perifusion with sex steroids. RT-PCR revealed no product for ER, but only for PR, in placentae across all gestational ages. Binding studies with labeled E and P showed no binding for either compound. Taken together, these observations suggest the presence of PR, but not of ER, in human placenta throughout gestation. Our failure to detect the ER does not entirely preclude the presence of this receptor in human trophoblasts, but might be attributed to a relatively low number and density of ER on these cells. Alternatively, estrogen's action on the placenta may be mediated by a different type of ER, such as by a non-classical membrane-bound receptor.

Binding Sites↗
PubMed1995

Relaxin triggers calcium transients in human granulosa-lutein cells.

Although the peptide hormone relaxin is synthesized by the human corpus luteum in vivo, its potential to serve as a local factor in the regulation of luteal function is not clear. Using an enzyme-linked immunosorbent assay for human relaxin, we detected relaxin in the culture medium of human granulosa-lutein cells as early as after 6 days in culture. Moreover, 1 x 10(5) IU/l human chorionic gonadotropin stimulated relaxin release about fourfold during a 48-h incubation on culture days 6-8 (and 7-9), but not earlier (on days 1, 3 and 4). The stimulatory action of human chorionic gonadotropin on progesterone release was not influenced by relaxin, and relaxin alone was without stimulatory effect. However, human recombinant relaxin (between 0.1 and 12.5 micrograms/l) increased intracellular free Ca2+ basal levels to maximal peak levels exceeding 1000 nmol/l in about 64% of all tested cells (N = 168) with no obvious dependency on the culture day. The relaxin-induced Ca2+ signal was not affected by removal of extracellular Ca2+. As depletion of intracellular Ca2+ stores by ionomycin rendered the cells unresponsive to relaxin or diminished their ability to respond, these results point to an intracellular source of the Ca2+ signal. In summary, our data indicate the presence of a functional relaxin receptor on human granulosa-lutein cells, which is linked to Ca2+ release from intracellular stores.

Calcium↗
PubMed1995

Measles virus-specific dsRNAs are targets for unwinding/modifying activity in neural cells in vitro.

Biased hypermutation events found predominantly in the matrix gene of measles virus isolated from persistent human CNS infections have been attributed to the action of a cellular unwinding/modifying activity (UMA). To define the level and distribution of this activity in brain cells, fractionated extracts were prepared from the nuclei and cytoplasm of human glioblastoma (D-54, U-251) and neuroblastoma (IMR-32, SKN-MC) cells and analyzed for their ability to modify synthetic dsRNAs specific for the measles virus (MV) matrix (M) gene. On a quantitative basis we could show that the activity localized to both the nuclear and cytoplasmic compartments of both cell types analyzed independent of cell proliferation. The presence of significant levels of UMA in the cytoplasm of human brain cells following growth arrestment in vitro with retinoic acid supports the interpretation that UMA may contribute to the attenuation of MV gene functions during the primary infection of brain cells, thereby supporting the establishment of virus persistence.

Cell Differentiation↗
PubMed1994

Synaptobrevin cleavage by the tetanus toxin light chain is linked to the inhibition of exocytosis in chromaffin cells.

Exocytosis of secretory granules by adrenal chromaffin cells is blocked by the tetanus toxin light chain in a zinc specific manner. Here we show that cellular synaptobrevin is almost completely degraded by the tetanus toxin light chain within 15 min. We used highly purified adrenal secretory granules to show that synaptobrevin, which can be cleaved by the tetanus toxin light chain, is localized in the vesicular membrane. Proteolysis of synaptobrevin in cells and in secretory granules is reversibly inhibited by the zinc chelating agent dipicolinic acid. Moreover, cleavage of synaptobrevin present in secretory granules by the tetanus toxin light chain is blocked by the zinc peptidase inhibitor captopril and by synaptobrevin derived peptides. Our data indicate that the tetanus toxin light chain acts as a zinc dependent protease that cleaves synaptobrevin of secretory granules, an essential component of the exocytosis machinery in adrenal chromaffin cells.

Amino Acid Sequence↗
PubMed1993

Purification and properties of N5-methyltetrahydromethanopterin:coenzyme M methyltransferase from Methanobacterium thermoautotrophicum.

N5-Methyltetrahydromethanopterin:coenzyme M meth-yltransferase is an integral membrane protein found in methanogenic archaea. It catalyzes an energy-conserving step in methane formation from CO2 and from acetate. The enzyme from Methanobacterium thermoautotrophicum (strain Marburg) has been purified 30-fold to apparent homogeneity. The purified enzyme had an apparent molecular mass of 670 kDa and was composed of seven different polypeptides of 34 kDa, 28 kDa, 24 kDa, 23 kDa, 21 kDa, 13 kDa, and 12 kDa. The N-terminal amino acid sequences of these polypeptides were determined. The native 670-kDa enzyme was found to contain 7.6 mol 5-hydroxybenzimidazolyl cobamide/mol, 37 mol non-heme iron/mol and 34 mol acid-labile sulfur/mol. Cobalt analyses after sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed that the corrinoid was bound to the 23-kDa polypeptide. The apparent molecular masses of the polypeptides given above were determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis without boiling the samples prior to analysis. When the samples were boiled, as is usually done, the 23-kDa polypeptide changed its apparent molecular mass to 33 kDa and the 21-kDa, 24-kDa, and 28-kDa polypeptides formed aggregates. The specific activity (apparent Vmax) of the purified methyltransferase preparation was 11.6 mumol.min-1.mg protein-1. The apparent Km for N5-methyltetrahydromethanopterin was 260 microM and that for coenzyme M was 60 microM. The preparation was absolutely dependent on the presence of Ti(III) for activity. ATP enhanced the activity 1.5-2-fold.

Amino Acid Sequence↗
PubMed1991

[Retrospective study of 412 aortic valve replacements by Bjork-Shiley prosthesis implanted between January 1972 and October 1984. Actuarial survival, mortality, complications].

Between January 1972 and October 1984, 412 aortic valve replacements by Bjork-Shiley disk prosthesis were performed. 183 patients suffered from aortic incompetence, 132 from an aortic disease and 97 from aortic stenosis. 116 associated procedures (28%) were performed = 36 myocardial revascularizations, 61 Bentall operations, 12 patch grafts to the ascending aorta and 7 Wheat operations. The mean age was 53.6 years and 25% of the patients were over the age of 65 years. Fifty percent of the patients had stage III or IV disease according to the NYHA classification. The cardiac index was less than 2.3 l/min/m2 in 44.26% of cases. The early postoperative mortality was 4.85% and 20% of these deaths were related to the prosthesis. The late mortality was 17.25%, with 20% of deaths related to the valve. The mean follow-up 59.75 +/- 2 months (range: 1 to 166 months) with a cumulative survival of 2.092 patients-years. It was significantly influence by the existence of preoperative angina, another operation associated with AVR and a cardiac index less than 2.3 l/min/m2. Seventy-one complications were related to the prosthesis including dysfunction (0.05% patient-year), 3 valve thromboses (0.15% patient-year), 6 infected valves (0.31% patient-year), 12 cases of peri-prosthetic dehiscence (0.61% patient-year), 10 embolic complications (0.61% patient-year) and 37 complications related to anticoagulants, including 26 major complications (1.48% patient-year). The valve failure rate was 1.19% patient-year. The results of our series are comparable to those reported in the literature, which confirm the reliability of the Bjork-Shiley Valve.

Actuarial Analysis↗
PubMed1989

Norepinephrine in reflex sympathetic dystrophy: an hypothesis.

Reflex sympathetic dystrophy (RSD) usually occurs in an individual who has been experiencing significant personal stress, a state associated with increased discharge of norepinephrine (NE) from perivascular postganglionic sympathetic neurons. RSD is often precipitated by this sequence: traumatic arterial spasm, regional ischemia, neurogenic inflammation, and ischemic/edematous damage to membranes of preterminal perivascular nociceptive neurons. In the natural repair of these membranes, it is suggested that adrenoceptors appear and are ordinarily transitory; but in RSD, they are retained by the increased adjacent NE. This process delays further healing, produces pain, and releases inflammatory substances, resulting in interacting pathophysiologic vicious cycles.

Humans↗
PubMed1980

Prolonged relief of tic douloureux from partial root destruction is associated with localized analgesia.

Fifty-eight patients who had been relieved of tic douloureux (TD) for least 3 years after partial destruction of the trigeminal sensory root by injection of minimal amounts of alcohol were reexamined 3 1/2 to 21 years after treatment. Of 41 patients still in remission at a median of 10 years after treatment, 32 had analgesia; i.e., sensation of pain from pinprick was absent in all 52 originally neuralgic areas. The other 9 patients in remission had some pain on pinprick in their neuralgic areas. In contrast, of 17 patients with recurrence of TD 3 1/2 to 11 years (median, 6 years) after treatment, at least 15 had demonstrable pain on pinprick in the neuralgic areas. It is concluded that continuing absence of pain on pinprick in the affected facial mucocutaneous area (or areas) is associated with prolonged relief of tic douloureux.

Denervation↗