Search PubMed⌕ Search

Biomedical subjects

A Hermann

Publications and source records attributed to A Hermann.

At least 55 records · Page 3Linked to original sources
PubMed1998

Determination of the (13)C Content of Glycerol Samples of Different Origin.

The average carbon isotope value (delta(13)C) of 63 samples of glycerol from over 30 different sources has been determined. The results indicate that it is possible to distinguish the glycerol obtained from the glycerides produced in plants following C-3 and C-4 carbon fixation pathways. The samples obtained from animal sources seem to reflect the composition of the material consumed, as well as that produced by sugar fermentation.

Journal Article↗
PubMed1998

Nitric oxide-mediated cGMP synthesis in Helix neural ganglia.

The central nervous system of the mollusc Helix pomatia was stimulated with NO donors sodium nitroprusside (SNP), S-nitroso-N-acetylpenicillamine (SNAP) or hydroxylamine, in the presence of a phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine (IBMX). Radioimmunoassay revealed that all of the three NO donors significantly increased cGMP levels by 22-27-fold above basal levels. Compared with controls, strong cGMP immunoreactivity was observed in axons and cytoplasm of the stimulated neurons. About 80% of cGMP-immunoreactive neurons colocalized with NADPH-diaphorase activity. Some glial cells and giant neurons were not stained by NADPH-diaphorase histochemistry but were cGMP-immunoreactive. The results suggest the existence of a NO/cGMP pathway and indicate NO as an intra- and intercellular signaling molecule in the Helix central nervous system.

Animals↗
PubMed1998

External action of di- and polyamines on maxi calcium-activated potassium channels: an electrophysiological and molecular modeling study.

In this study we compared polyamines to various diamines, and we modeled flexibility as well as hydrophobicity properties of these molecules to examine possible structural differences that could explain their external effects on the channels. The natural polyamines (putrescine, cadaverine, spermidine, spermine) and diamines increasing in CH2 chain length from C2 to C12 were used to probe maxi calcium-activated potassium (BK) channels in GH3 pituitary tumor cells when applied extracellularly. In single-channel recordings we found polyamines as well as diamines up to 1,10-diaminodecane to be ineffective in altering channel current amplitudes or kinetics. In contrast, 1,12-diamino dodecane (1,12-DD) was found to be a reversible blocker, with a blocking site at an electrical distance (z delta) of 0.72 within the channel. It reduced single-channel current amplitude, mean channel open time, and channel open probability. In computer simulations structural data, such as flexibility, hydration, and log D values, were calculated. 1,12-DD showed the largest flexibility of all diamines (minimum N-N distance 9.9 A) combined with a marked hydrophobicity due to a 4-5 A hydrophobic intersegment between hydrophilic ends in the molecule, as confirmed by GRID water probe maps and a log D value of -1.82 at pH 7.2. We propose that the amount of hydration of the molecule, more than its flexibility, constitutes an essential parameter for its ability to act as a channel blocker.

Animals↗
PubMed1998

Well-differentiated versus less-differentiated endometrial carcinoma.

The aim of this study was to compare well-differentiated (grade 1) and less-differentiated (grades 2 and 3) endometrial carcinoma, concerning clinical risk factors, presenting symptoms and operative findings. Seventy-one surgically staged endometrial carcinoma cases were reviewed and retrospectively divided according to tumor differentiation into two groups: grade 1 cases (Group I; n=40) and grade 2 and 3 cases (Group II; n=31). No difference was found between the two groups when comparing patient age, gravidity and parity, history of hypertension, diabetes or other malignancies, duration of menopause, number of patients receiving hormonal replacement therapy and histological type of tumor. There was also no difference in presenting symptoms or in duration of uterine bleeding up to the diagnosis of endometrial carcinoma. On the other hand, patients with well-differentiated tumors, as compared to patients with less-differentiated endometrial carcinoma, were significantly more obese (p<0.02), had a smaller uterus (p<0.01) and presented with less advanced stage disease (p<0.0005). The fact that the age of the patients, as well as the duration of uterine bleeding before diagnosis, was similar in both groups may indicate that more advanced cases, as in group II, represent originally a more aggressive tumor rather than progression from a well-differentiated disease. This hypothesis needs further research.

Aged↗
PubMed1997

Ethanol suppresses neuronal Ca2+ currents by effects on intracellular signal transduction.

The mechanism of action of ethanol on voltage-activated Ca2+ currents in neurons of the mollusk, Helix pomatia, was studied focusing on intracellular signaling. Ethanol suppressed inward Ca2+ currents in a time- and voltage-dependent manner. Buffering of intracellular Ca2+ with bis(o-aminophenoxy)ethane-N,N,N',N-tetraacetic acid (BAPTA) abolished the ethanol effects on Ca2+ currents. Intracellular GTP-gamma-S injection decreased Ca2+ currents whereas GDP-beta-S injection was ineffective. Ethanol had no further blocking effect on Ca2+ currents in GTP-gamma-S injected cells. In the presence of dopamine, which is known to suppress Ca2+ currents by G0-protein activation, ethanol application was ineffective. The protein kinase C (PKC) blockers, staurosporine and chelerythrine, prevented the ethanol effects on Ca2+ currents. The PKC activators, 1,2-oleoylacetylglycerol (OAG) and beta-phorbol-12,13-dibutyrate (PdBu), both, after maximum stimulation, also occluded the effect of ethanol on Ca2+ currents, whereas in the presence of 4-alpha-phorbol-12,13-didecanoate (4-alpha-PDD), an ineffective phorbol ester, ethanol suppressed Ca2+ currents. Ethanol increased the threshold of Ca2+-dependent action potentials and decreased their duration. Our results indicate that the suppression of voltage-activated Ca2+ currents by ethanol and its effects on action potentials involve activation of a G-protein/protein kinase transduction pathway.

Action Potentials↗
PubMed1997

Ethanol activates maxi Ca2+-activated K+ channels of clonal pituitary (GH3) cells.

The effect of ethanol on maxi Ca2+-activated K+ channels (BK channels) in GH3 pituitary tumor cells was investigated using single-channel recordings and focusing on intracellular signal transduction. In outside-out patches, ethanol caused a transient concentration-dependent increase of BK-channel activity. 30 mm (1.4 per thousand) ethanol significantly increased mean channel open time and channel open probability by 26.3 +/- 9% and 78.8 +/- 10%, respectively; single-channel current amplitude was not affected by ethanol. The augmenting effect of ethanol was blocked in the presence of protein kinase C (PKC) inhibitors staurosporine, bisindolylmaleimide, and PKC (19-31) pseudosubstrate inhibitor as well as by AMP-PNP (5'-adenylylimidodiphosphate), a nonhydrolyzable ATP-analogue, but not by the phospholipase C blocker U-73122. Phosphatase inhibitors microcystin-LR and okadaic acid promoted the ethanol effect. The blocking effect was released at higher concentrations of ethanol (100 mm) suggesting a second site of action or a competition between blockers and ethanol. Our results suggest that the effect of ethanol on BK-channels is mediated by PKC stimulation and phosphorylation of the channels which increases channel activity and hence may influence action potentials duration and hormone secretion.

Animals↗
PubMed1997

Annexin-immunoreactive proteins in the nervous system and eye of the gastropods, Aplysia and Helix.

We studied the distribution of annexin I- and annexin V-like proteins in the eye and central nervous system of the snails, Aplysia californica and Helix pomatia by immunocytochemistry. Annexin I-immunoreactive material in Aplysia californica was localized in sensory and corneal cells of the eye and in distinct neurons of the cerebral, buccal, and abdominal ganglia, where it was exclusively located in bag cells. Annexin V-immunoreactive neurons were restricted to the pleural ganglia of Aplysia californica. In Helix pomatia annexin I-immunoreactive neurons were present in the cerebral, buccal, visceral, and left and right parietal ganglia, whereas annexin V-immunoreactivity neurons were present in left and right pleural, left and right parietal, visceral, and buccal ganglia. Annexin VI-immunoreactivity was absent in both gastropods studied. Our study shows a cell specific localization of annexin-like proteins in the central nervous system and eye of molluscs. The cell types containing the immunoreactive proteins suggests that the annexin-like proteins may be involved in intracellular signaling mechanisms, which ultimately may modulate egg-laying and circadian rhythmicity.

Animals↗
PubMed1997

Oxidation of apolipoprotein(a) inhibits kringle-associated lysine binding: the loss of intrinsic protein fluorescence suggests a role for tryptophan residues in the lysine binding site.

Lipoprotein(a) [Lp(a)] is a low-density lipoprotein complex consisting of apolipoprotein(a) [apo(a)] disulfide-linked to apolipoprotein B-100. Lp(a) has been implicated in atherogenesis and thrombosis through the lysine binding site (LBS) affinity of its kringle domains. We have examined the oxidative effect of 2,2'-azobis-(amidinopropane) HCl (AAPH), a mild hydrophilic free radical initiator, upon the ability of Lp(a) and recombinant apo(a), r-apo(a), to bind through their LBS domains. AAPH treatment caused a time-dependent decrease in the number of functional Lp(a) or r-apo(a) molecules capable of binding to fibrin or lysine-Sepharose and in the intrinsic protein fluorescence of both Lp(a) and r-apo(a). The presence of a lysine analogue during the reaction prevented the loss of lysine binding and provided a partial protection from the loss of tryptophan fluorescence. The partial protection of fluorescence by lysine analogues was observed in other kringle-containing proteins, but not in proteins lacking kringles. No significant aggregation, fragmentation, or change in conformation of Lp(a) or r-apo(a) was observed as assessed by native or SDS-PAGE, light scattering, retention of antigenicity, and protein fluorescence emission spectra. Our results suggest that AAPH destroys amino acids in the kringles of apo(a) that are essential for lysine binding, including one or more tryptophan residues. The present study, therefore, raises the possibility that the biological roles of Lp(a) may be mediated by its state of oxidation, especially in light of our previous study showing that the reductive properties of sulfhydryl-containing compounds increase the LBS affinity of Lp(a) for fibrin.

Amidines↗
PubMed1997

Evidence for bradykinin B2-receptors on cultured human decidua cells.

Bradykinin is known to be present at sites of acute inflammation and to exert its potent inflammatory effects mainly via the bradykinin B2-receptor. Recently, bradykinin dependent processes have been described in cultured human decidual cells, so that bradykinin may expand the list of paracrine factors involved in labour induction. In this paper we present the results of in vitro studies giving evidence that these cells carry the bradykinin B2-receptor. By immunocytochemical methods the receptor protein was localized on decidual cells. Analysis of cellular extracts of cultured decidual cells by RT-PCR showed the presence of the specific mRNA coding for the bradykinin B2-receptor. Binding studies revealed a single, saturable and specific binding site for bradykinin of high affinity (Kd = 0.85 nM, Bmax = 436 fmol/mg protein). Competitive binding studies showed displacement of [3H]-bradykinin by HOE 140, but not by the ligands for the bradykinin B1-receptor, des-Arg10-kallidin and [Leu8]-des-Arg9-bradykinin. The results are consistent with the presence of the bradykinin B2-receptors.

Adrenergic beta-Antagonists↗
PubMed1997

Biochemical characterization and histochemical localization of nitric oxide synthase in the nervous system of the snail, Helix pomatia.

Nitric oxide synthase (NOS) in the snail Helix pomatia was characterized by biochemical and molecular biological techniques and localized by histochemical methods. Central ganglia contained particulate paraformaldehyde-sensitive and cytosolic paraformaldehyde-insensitive NADPH-diaphorase. The cytosolic NADPH-diaphorase activity coeluted with NOS activity. The activity of NOS was dependent on Ca2+ and NADPH and was inhibited by N(G)-nitro-L-arginine (L-NNA). Proteins purified by 2',5'-ADP affinity chromatography were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and migrated at 150, 60, 40, and 30 kDa. An antibody to mammalian NOS exclusively labeled the 60-kDa protein. Characterization of the cDNA of the corresponding 60-kDa NOS-immunoreactive protein revealed no sequence homology with any known NOS isoform. The recombinant protein exhibited Ca2+- and NADPH-dependent NOS activity, which was partially inhibited by EGTA and L-NNA. Histochemistry showed NADPH-diaphorase activity in discrete regions of the central and peripheral nervous system. About 60% of the NADPH-diaphorase-positive neurons colocalize with immunoreactive material detected by antibodies to mammalian NOS. Comparison of organs showed the highest NADPH-diaphorase activity in the nervous system, whereas moderate activity was present in muscle tissue, digestive tract, and gonads. Our study suggests the presence of NOS and a putative NOS-associated/regulating protein in mollusk nervous tissue.

Animals↗
PubMed1997

Bradykinin stimulates interleukin-6 and interleukin-8 secretion of human decidua derived cells.

Cytokines are known to participate in the process of parturition within a paracrine network in fetal membranes. Bradykinin can also contribute to this process, increasing the release of eicosanoids from decidua cells. In this study, we present evidence for a cross-link between bradykinin and the cytokines. Short and long term cultures of human decidua cells were incubated for 4 h and 24 h with and without bradykinin. IL-6 and IL-8 were determined in the supernatants by ELISA. Results show a large interindividual variability in the basal secretion of IL-6 and IL-8 and a clear increase in the secretion of both ILs in response to bradykinin. By this amplifying effect on cytokine secretion, bradykinin can initiate local and systemic effects of amniochorionitis.

Bradykinin↗
PubMed1997

[Uterine metastasis of invasive lobular breast carcinoma. Case report and review of the literature with reference to differential diagnostic problems and clinical consequences].

Uterine metastases of malignant tumours are rare. Among extragenital malignancies breast cancers of the lobular type most likely spread out to this site. The respective diagnosis is rendered more difficult by the late onset of clinical symptoms that may imitate the picture of primary uterine cancer. We report on a patient with advanced invasive lobular breast cancer (ILC) where this form of metastazation was detected after conization for PAP IVa. Especially in patients with advanced lobular breast cancer and suspicious symptoms (such as pathologic PAP-Smear, conspicuous colposcopic finding, vaginal bleeding, growth-progressive uterus and hyperplastic endometrium) the possibility of uterine metastases should be included in preoperative planning.

Breast Neoplasms↗
PubMed1996

gamma-Aminobutyric acid enhances the light response of ganglion cells in the trout pineal organ.

Electrical recordings from achromatic second order neurons of intact superfused pineal organs of the rainbow trout were used to investigate the role of gamma-aminobutyric acid (GABA) in the transmission of photoreceptor signals onto centrally projecting ganglion cells. Bath-applied GABA decreased the spike discharge rate of 98% of achromatic ganglion cells in a dose-dependent manner. GABA was also active if applied during synaptic blockade, demonstrating the presence of GABAergic receptors at the ganglion cell level. Responsiveness of ganglion cells to light was reversibly enhanced by GABA. The light response curve of ganglion cells, which was obtained by plotting spike rate versus light intensity, was significantly shifted to lower frequencies by GABA, indicating that GABA is an important inhibitory modulator of ganglion cell activity in the trout pineal organ.

Action Potentials↗
PubMed1996

S-100-immunoreactivity in spontaneously active snail neurons.

The distribution of S-100-immunoreactive material was examined in the central nervous system of the gastropod snail. Helix pomatia, and electrophysiological properties of S-100-positive neurons were characterized. Immunocytochemical studies revealed S-100-like protein to be present in neurons localized in the cerebral, left parietal, and visceral ganglia, but not in glial cells. Among the immunoreactive neurons we identified the giant cells LPa3 and LPa4. Western blots showed a single S-100-immunoreactive band at 12-14 kDa. S-100-positive neurons are distinguished by spontaneous discharge activity in a beating or bursting mode and a prominent Ca(2+)-activated potassium outward current. Our result show that a S-100-like protein exclusively present in neurons of the Helix central nervous system is correlated with spontaneous discharge activity of these cells.

Animals↗
PubMed1996

Ethanol actions on the mechanisms of Ca2+ mobilization in rat hippocampal cells are mediated by protein kinase C.

The effects of ethanol on intracellular free Ca(2+) concentration, [Ca](i), were studied in cultured rat hippocampal neurons using fluo-3 and confocal microscopy. Ethanol application transiently elevAted [Ca](i) due to Ca(2+)-induced Ca(2+) release from internal stores since the effect was observed also in solutions containing zero Ca(2+) or 0.3 mM La(3+) and restoration of external Ca(2+) content led to secondary response in presence of ethanol. The sites of highest [Ca]i increases correlated well with those obtained after Ca(2+) release from caffeine-and IP3-sensitive internal stores. After single ethanol exposure the caffeine-evoked [Ca](i) transients were potentiated whereas Ca(2+) release induced by IP(3)-mobilizing agonists was suppressed. Similar effects were observed by activation of protein kinase C (PKC) by phorbol esters which also occluded ethanol actions. Ethanol increased fluorescence of Rim-1, a PKC indicator dye. The data obtained are consistent with ethanol activation of PKC whereby Ca(2+) release via ryanodine receptors is potentiated and IP(3) receptors are down-modulated. Since the effects of both ethanol and phorbol esters were mimicked by cytochalasins B and D, PKC-induced cytoskeleton phosphorylation and its subsequent rearrangements can be responsible for observed effects.

Animals↗
PubMed1996

The B2 receptor on cultured human decidua cells: release of arachidonic acid by bradykinin.

In vitro studies on cultured human decidual cells present evidence for the expression of the bradykinin B2 receptor. This protein was localized by immunocytochemical methods at the cellular plasma membrane and the mRNA was found in cellular extracts by RT-PCR. As a biological effect the release of 14C-AA was observed. Cells that had been incubated for 24 h with 14C-AA showed a bradykinin (BK)-induced release of radioactivity into the culture medium. This response was prevented by the specific bradykinin B2 receptor antagonist HOE 140. Pretreatment with LPS resulted in an increase of the spontaneous release of radioactivity. Adding BK, a further release of about 40-50% was to be shown. We conclude that BK can play a role in the case of bacterial infection of the fetal membranes AND may stimulate labour by an augmented production of prostaglandins.

Arachidonic Acid↗
PubMed1996

High and low molecular weight kininogen and plasma prekallikrein/plasma kallikrein in villous capillaries of human term placenta.

This study examined the expression and presence of components of the kallikrein-kinin system in human term placenta. Immunohistochemical studies localized H-kininogen and plasma prekallikrein/plasma kallikrein to endothelial cells of placental villous capillaries. In larger placental blood vessels and umbilical cord, neither kininogens nor kallikreins were detected. High (H) and low (L) molecular weight kininogen, plasma prekallikrein and plasma kallikrein were detected by Western blot analysis in human term placenta and in maternal and fetal blood, whereas tissue kallikrein was not. Furthermore, mRNA of plasma prekallikrein was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) in placental homogenates, while mRNA of H-kininogen, L-kininogen and tissue kallikrein was not. Because H-kininogen and plasma prekallikrein circulate in a complexed form, we suggest that endothelial cells bind kininogen and plasma prekallikrein in which they are secreted by the fetal liver from fetal blood. The co-localization of kininogen and plasma prekallikrein/plasma kallikrein suggests that kinins could be generated locally in placental capillaries. When released, they may play a role in regulating placental blood flow and transplacental transport of substrates and metabolites.

Capillaries↗