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Biomedical subjects

W Hanke

Publications and source records attributed to W Hanke.

At least 91 records · Page 5Linked to original sources
PubMed1994

Modulation of K(+)-channels in p-neurones of the leech CNS by phosphorylation.

Two types of potassium channels of identified (p-) neurones of the leech (Hirudo medicinalis) were investigated by using the patch-clamp technique. The open-state probability of these channels in cell-attached patches can be reduced by addition of 5-hydroxytryptamine to the bath solution. After excising the patches the application of alkaline phosphatase to the cytosolic face of the patch increases the open probability. The 5-HT1A-receptor agonist buspirone mimics the effect of 5-HT. Our experiments show that the effect of 5-HT might be due to a channel phosphorylation via a 5-HT1A-receptor subtype.

Alkaline Phosphatase↗
PubMed1994

Regulation of interrenal secretion in the axolotl, Ambystoma mexicanum.

The regulation of corticosteroid secretion of the adrenal cortex (interrenal tissue) of axolotl (Ambystoma mexicanum) was studied using in vitro preparations of kidney containing interrenal tissue. Normally, 0.3-0.65 ng/5 min corticosterone and 0.15-0.3 ng/5 min aldosterone were released from the tissue. Regulatory peptides were effective in the following range: ACTH = arginine vasotocin > urotensin II > angiotensin II. They stimulate an elevation of corticosterone (plus 0.2-1 ng/5 min) and of aldosterone (plus 0.05-0.15 ng/5 min). The three primary effector systems leading to second messengers, adenylate cyclase (forming cAMP), phospholipase C (forming InsP3 + DAG), and phospholipase A2 (liberating arachidonic acid) are involved in stimulation of biosynthesis. It can be suggested that the second messengers stimulate the biosynthesis at the level of the steps between pregnenolone and corticosterone ('3 beta-hydroxysteroid-dehydrogenase etc.), because the release of corticosterone is more stimulated than aldosterone. This is different than the regulation of anuran interrenal tissue. Ca++ ions are involved in corticosterone secretion. Verapamil inhibits immediately the secretion of corticosteroids and elevation of external Ca++ stimulates the release. It is suggested that Ca++ mediates the secretion process itself. Metamorphosis does not change the response of the interrenal gland compared with the neotenic animal.

Adrenocorticotropic Hormone↗
PubMed1994

Role of the atrial natriuretic peptide for adrenal regulation in the teleost fish Cyprinus carpio.

The biological role of atrial natriuretic peptide (ANP) for the adrenal tissue of the teleost fish Cyprinus carpio, the carp, was investigated using in vitro autoradiography to study ANP binding sites, immunohistochemistry to localize ANP-like peptides, and in vitro perifusion to measure adrenal cortisol and catecholamine release. 125I-labeled rat ANP-(99-126) [125I-rANP-(99-126)] binding was present in adrenal tissue exhibiting positive cooperativity with a half-maximal binding concentration (EC50) of 87 +/- 15 pM and a maximal binding capacity (Bmax) of 56 +/- 11 amol/mm2 (n = 3). 125I-rANP-(99-126) binding was competitively displaced by unlabeled ANP analogues with an intact disulfide bridge showing a lower affinity than the iodinated ligand. By the use of immunohistochemistry, ANP immunoreactivity was found in the majority of the phenylethanolamine N-methyl-transferase-immunoreactive, i.e., epinephrine-synthesizing cells. In vitro, ANP elevated both basal and acetylcholine-stimulated cortisol release by carp adrenal tissue, whereas adrenal catecholamines were significantly affected only in acetylcholine-stimulated epinephrine secretion. Thus ANP derived from the ANP-immunoreactive chromaffin cells of the carp adrenal seems to act in an autocrine and/or paracrine manner on steroidogenic interrenal and catecholaminergic chromaffin cells. Furthermore, the study indicates that the ANP effects on fish catecholamine and steroid release are reversed in mammals.

Acetylcholine↗
PubMed1994

[The role of long-term exposure to lead in the pathogenesis of hypertension--review of epidemiologic studies].

Epidemiological studies aimed at assessing the relationship between a long-term exposure to lead and hypertension were reviewed. The analysis of mortality based on blood lead levels (600-800 micrograms/l) indicated that the magnitude of exposure to lead was in general rather high. Deaths caused by cerebrovascular diseases proved to be the main risk in this group of population. The confirmation of this finding was looked for in studies of morbidity carried out in the working population and among people living in areas of high exposure to lead. The studies confirmed a significant relationship between the magnitude of exposure to lead and the level of systolic pressure. During those studies it was also attempted to monitor main confounding factors such as smoking and alcohol consumption. A clinical effect, namely an increased systolic pressure was, however, very low not exceeding several mm Hg and in terms of the difference in blood lead levels was equal to 10 micrograms/l. Despite all efforts mechanisms responsible for an increased pressure resulting from exposure to lead have not yet been identified. It seems most likely that disorders in metabolism of calcium ions leading to a spasm of muscular coat of vessels are a causal factor. There is an urgent need for assessing delayed effects of exposure to lead. Such studies should be performed in groups of persons with good evidence to prove their exposure to this factor. It would be helpful to describe individual doses corresponding to the magnitude of exposure to individual persons under study but that seems to be rather impossible in retrospective studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Confounding Factors, Epidemiologic↗
PubMed1993

Self-sustained spreading depressions in the chicken retina and short-term neuronal-glial interactions within the gray matter neuropil.

The chicken retina is an accessible piece of intact gray matter in which a self-sustained form of the 'Spreading Depression' (SD) wave can be easily elicited and recorded for many hours with double barrel ion-sensitive electrodes in the extracellular space. The blockade of glial (Müller) cell potassium channels with barium chloride added to the perfusing Ringer depressed both the negative potential shift typical of SDs and the velocity of spread. Moreover, there was separation of the extracellular increase of potassium and the drop in the extracellular potential: the peak of the potassium wave was increased, as well as its duration whereas the potential wave could be depressed to zero or even inverted to positive. By contrast the transient extracellular calcium drop could not be separated from the extracellular potential wave but appeared related to it: no transient calcium drop was observed when the negative potential was completely depressed or inverted. Both, the amplitude of the extracellular potential and extracellular calcium activity appeared to be important factors controlling the velocity of spread.

Animals↗
PubMed1993

Single ion channel currents in neuropile glial cells of the leech central nervous system.

The patch-clamp technique was used to investigate the activity of single ion channels in neuropile glial (NG) cells in the central nervous system (CNS) of the medicinal leech, Hirudo medicinalis. We found evidence for two distinct Cl- channels that could be distinguished by their basic electrical properties and their responses to different inhibitors on single ion channel currents. In the inside-out configuration in symmetrical Cl- solutions, these channels showed current-voltage relationships with slight outward rectification, mean conductances of 70 and 80 pS, and reversal potentials near 0 mV. Significant permeability to Na+, K+, or SO4(2-) could not be detected. The open-state probability of the 70 pS Cl- channel increased with membrane depolarization, whereas the open-state probability of the 80 pS Cl- channel was voltage-independent. The application of the stilbene derivative DIDS (100 microM) to the cytoplasmic side of the glial cell membrane blocked both Cl- channels. The activity of the 70 pS channel was blocked irreversibly by DIDS, whereas the activity of the 80 pS channel reappeared after wash-out of DIDS. Both channels were blocked reversibly by 1 mM Zn2+. K+ channels could only be observed occasionally in the soma membrane of the NG cells. We have characterized a 60 pS K+ channel with a high selectivity for K+ over Na+. The low density of K+ channels in the soma membrane may indicate a non-uniform distribution of this channel type in NG cells.

Action Potentials↗
PubMed1993

Receptors for atrial natriuretic factor (ANF) in kidney and adrenal tissue of urodeles--lack of angiotensin II (A II) receptors in these tissues.

Binding sites for atrial natriuretic factor (ANF) and angiotensin II (A II) were localized and quantified in renal and adrenal tissue of the Urodele Ambystoma mexicanum by quantitative in vitro autoradiography using 125I-ratANF(99-126) and 125I-[Val5]-A II or 125I-human A II as labeled ligands. Specific 125I-ratANF(99-126) binding was present in glomeruli, renal tubules, and adrenal tissue. ANF had heterogeneous binding sites exhibiting positive cooperativity with a half maximal binding concentration (EC50) of 124 +/- 12 pM in glomeruli and 118 +/- 18 pM in adrenal tissue (n = 8). The corresponding maximal binding capacities (Bmax) were 0.84 +/- 0.10 and 0.72 +/- 0.18 femtomol/mm2. 125I-ratANF(99-126) binding was competitively displaced by unlabeled ANF analogues with an intact disulfide bridge showing a lower affinity than the iodinated ligand. In in vitro perifusion experiments ANF inhibited basal as well as ACTH-stimulated steroid secretion whereas catecholamine release was not affected indicating that ANF binding in adrenal tissue is restricted to steroidogenic interrenal cells. In vivo experiments demonstrated that during acclimation to 1.5% salt water made using seawater salt the number of ANF binding sites in kidney glomeruli decreased after 12 hr and 7 days while no significant changes were observed in adrenal tissue. No A II binding sites were detected either in renal or adrenal tissue indicating a lack of A II receptors in these tissues, which was confirmed by in vitro perifusion experiments which showed that A II did not affect adrenal steroid and catecholamine secretion.

Adrenal Cortex Hormones↗
PubMed1993

ATP-inhibited and Ca(2+)-dependent K+ channels in the soma membrane of cultured leech Retzius neurons.

The properties of one ATP-inhibited and one Ca(2+)-dependent K+ channel were investigated by the patch-clamp technique in the soma membrane of leech Retzius neurons in primary culture. Both channels rectify at negative potentials. The ATP-inhibited K+ channel with a mean conductance of 112 pS is reversibly blocked by ATP (Ki = 100 microM), TEA (Ki = 0.8 mM) and 10 mM Ba2+ and irreversibly blocked by 10 nM glibenclamide and 10 microM tolbutamide. It is Ca2+ and voltage independent. Its open state probability (Po) decreases significantly when the pH at the cytoplasmic face of inside-out patches is altered from physiological to acid pH values. The Ca(2+)-dependent K+ channel with a mean conductance of 114 pS shows a bell-shaped Ca2+ dependence of Po with a maximum at pCa 7-8 at the cytoplasmic face of the membrane. The Po is voltage independent at the physiologically relevant V range. Ba2+ (10 MM) reduces the single channel amplitude by around 25% (ATP, TEA, glibenclamide, tolbutamide, and Ba2+ were applied to the cytoplasmic face of the membrane). We conclude that the ATP-dependent K+ channel may play a role in maintaining the membrane potential constant--independently from the energy state of the cell. The Ca(2+)-dependent K+ channel may play a role in generating the resting membrane potential of leech Retzius neurons as it shows maximum activity at the physiological intracellular Ca2+ concentration.

Adenosine Triphosphate↗
PubMed1993

Mechanisms of hyperosmotic acclimation in Xenopus laevis (salt, urea or mannitol).

The acclimation of the clawed toad Xenopus laevis to hyperosmotic solutions of NaCl (balanced solution of sea salt), urea or mannitol was studied. The animals could not be acclimated to salt solutions more concentrated than 400 mosm.1-1. Urea was tolerated till 500 mmol.1-1. Plasma osmolality was always hyperosmotic to the environmental solution, but with diminished osmotic gradient at the highest tolerated solutions. Plasma urea concentration approached 90 mmol.1-1, similar in the three solutions of acclimation. Urine volume was very small under all conditions. Serum aldosterone and corticosterone did not differ significantly, although there was a slight tendency towards lower aldosterone in the NaCl solution. In vivo water uptake in tap water acclimated animals was very small, and was higher in the other groups. Only the salt- and urea-acclimated, but not the tap water and mannitol-acclimated groups responded with a clear increase following injection of oxytocin or theophylline. In vitro urea fluxes were similar and invariable in both directions under all conditions. No significant effect of theophylline was observed. Sodium transport measured by the short-circuit technique in vitro was lower in salt- and mannitol-acclimation conditions, and was stimulated significantly under all conditions in response to serosal oxytocin or theophylline. It is concluded that Xenopus laevis can osmoregulate at a limited range of external solutions. It is limited in the increase of its plasma urea concentration; the transport properties of the skin do not change very much upon acclimation, except for the hydroosmotic response to oxytocin.

Adaptation, Physiological↗
PubMed1993

Epidemiological evaluation of death risk from cardiovascular diseases among Polish population of working age.

"The aim of the study was an evaluation of death risk among men and women of working age exposed to cardiovascular risk factors. The survey covered random samples of the population living in the regions of Wroclaw and Ciechanow, [Poland,] including families of all who died from cardiovascular diseases in 1988.... The results of demographic analyses [indicate] that social factors exerting a negative effect on health behaviours are responsible for high mortality in males. Moreover, difficulties of Polish life place additional stress on male population.... For each from among 18 analysed factors the risk of death from cardiovascular diseases was several times higher in exposed males than in females."

Behavior↗
PubMed1992

Localization of binding sites for atrial natriuretic factor and angiotensin II in the central nervous system of the clawed toad Xenopus laevis.

The distribution of binding sites for atrial natriuretic factor (ANF) and angiotensin II (A II) was investigated in the central nervous system (CNS) of the clawed toad Xenopus laevis by means of in vitro autoradiography using [125I]-rat ANF(99-126) or [125I] [Val5] A II and [125I]human A II as labeled ligands. The highest densities of specific ANF-binding were detected in the nucleus habenularis, thalamic regions, hypophyseal pars nervosa and nucleus interpeduncularis. Moderate ANF-binding was found in the bulbus olfactorius, pallium, septum, striatum, lateral forebrain bundle, nucleus infundibularis, hypophyseal pars distalis and tectum. The highest levels of specific A II binding sites were observed in the nucleus praeopticus, nucleus habenularis, hypophyseal pars nervosa and pars distalis, whereas the amygdala contained moderate A II binding. The existence of specific binding sites for ANF and A II in the CNS of Xenopus laevis suggests that both peptides act as neurotransmitters or neuromodulators in the amphibian CNS. The co-localization of dense binding sites for both peptides in the nucleus habenularis, hypophyseal pars nervosa and pars distalis supports the view that ANF and A II have opposite regulatory functions in these regions.

Angiotensin II↗