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Biomedical subjects

F Wehner

Publications and source records attributed to F Wehner.

51 records · Page 3Linked to original sources
PubMed1991

Ba2+ release from soda glass modifies single maxi K+ channel activity in patch clamp experiments.

Glasses used to fabricate patch pipettes may release components which affect ion channels (Cota, G., and C.M. Armstrong. 1988. Biophys. J. 53:107-109; Furman, R.E., and J.C. Tanaka. 1988. Biophys. J. 53:287-292; Rojas, L., and C. Zuazaga. 1988. Neurosci. Lett. 88:39-44). The gating properties of maxi K+ channels from Necturus gallbladder epithelium depend on whether borosilicate glass (BG) or blue tip hematocrit glass (SG) is used to construct the patch pipettes. The data are consistent with solubilization from SG of a component which exerts voltage-dependent, cytosolic-side specific block, closely resembling "slow block" by Ba2+ ions. Ringer's solution preincubated with SG, but not with BG, blocked inside-out maxi K+ channels when used as bathing solution. Mass spectrometry revealed that Ba2+ is released by the glass from fast and slow-release compartments (SG contains 3% wt/wt BaO), and is the only ion found in the solution at concentrations consistent with the observed channel block. Additionally, SG released O2-, Na+, Ca2+, and Mg2+, all to micromolar concentrations. These elements do not interfere with maxi K+ channels but they could in principle alter the properties of other ion channels. Thus, screening for channel-modifying substances released by the glass may be necessary for the adequate interpretation of patch-clamp results.

Animals↗
PubMed1991

Electric properties of rat liver cell cultures on gas-permeable membranes.

In rat hepatocytes grown on gas-permeable membranes (Petzinger et al. In Vitro Cell. Dev. Biol. 24: 491-499, 1988), cellular and canalicular potentials as well as input resistances were measured using two-channel microelectrodes. In HCO3(-)-containing solutions, we found -30.9 +/- 0.4 (SE) (n = 141) and -13.9 +/- 1.4 mV (n = 22) for cell and canalicular membrane potentials, respectively. There was no dependence of these parameters on the age of the primary culture. Canalicular input resistance, however, increased from 13.3 +/- 2.0 M omega (n = 4) at day 1 after seeding to 36.1 +/- 5.0 M omega (n = 9) at day 2 and stabilized thereafter, while cell input resistance continuously decreased from 37.0 +/- 3.3 M omega at 1 h (n = 6) to 5.2 +/- 2.1 M omega (n = 27) at 3 days after preparation. In ion substitution experiments there were no changes in the transference numbers for K+, Na+, or Cl- that could account for this effect. Cable analysis, however, revealed that the decrease in input resistance reflects a time-dependent increase in electrical coupling between cells. We conclude that rat liver cells on gas-permeable membranes are highly suited for the quantitative analysis of cell-to-cell interaction. In addition, cells and canaliculi are readily accessible with two-channel microelectrodes, making this preparation a promising tool for electrophysiological analysis of hepatocellular transport mechanisms.

Animals↗
PubMed1990

Naloxone-insensitive transport effects of loperamide in guinea-pig gallbladder epithelium.

The effects of the antidiarrheal drug, loperamide, on HCO3 and Na transport across guinea-pig gallbladder epithelium were investigated using Ussing-chamber methods. Under basal conditions, mucosal loperamide (10(-4) mol/l) moderately lowered both the absorptive (JHCO3ms) and the secretory HCO3 flux (JHCO3sm) (pH-stat method), most likely by changing paracellular HCO3 flow. Exposure to serosal prostaglandin E1 (10(-6) mol/l) abolished Na absorption and turned HCO3 secretion electrogenic. The associated short-circuit current (Isc) was inhibited by loperamide in a concentration-dependent manner; mucosal addition (threshold at 3 x 10(-6) mol/l) of the drug was more effective. Inhibition of Isc was related to a decrease in JHCO3sm, but exceeded the drop in JHCO3net. The effects on JHCO3sm and Isc were mimicked by [Met5]enkephalin. Naloxone (10(-6) mol/l) was unable to influence the effects of loperamide and [Met5]enkephalin on Isc. There were no pro-absorptive effects of loperamide on unidirectional Na fluxes. We conclude that antisecretory properties of loperamide are solely due to inhibition of electrogenic HCO3 secretion, an effect unrelated to opiate receptor binding.

Alprostadil↗
PubMed1990

Transcellular bicarbonate transport in rabbit gallbladder epithelium: mechanisms and effects of cyclic AMP.

HCO3 permeation through rabbit gallbladder epithelium has been investigated in vitro using voltage-clamp, pH-stat and microelectrode techniques. Mucosa-to-serosa flux of HCO3 (approximately 4.9 mumol cm-2 h-1) was dependent on luminal Na and inhibited by amiloride (1 mmol/l, luminal bath), methazolamide (0.1 mmol/l, both sides), and ouabain (30 mumol/l, serosal bath). Maximal rates of serosa-to-mucosa flux of HCO3 (approximately 2.8 mumol cm-2 h-1) required serosal Na and mucosal Cl. This flux was inhibited by ouabain, 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid (1 mmol/l, serosal bath), and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (0.1 mmol/l, luminal bath). Ineffective were methazolamide (0.1 mmol/l, both sides) and amiloride (1 mmol/l, serosal bath). 8-Br-cAMP (1 mmol/l, serosal bath) largely inhibited the absorptive and moderately stimulated the secretory flux. In tissue conductance, short-circuit current, and transmural voltage prostaglandin E1 (1 mumol/l, serosal bath) and 8-Br-cAMP caused moderate to negligible increases. No significant alterations of apical membrane potential (approximately -65 mV) and the apparent ratio of membrane resistances (Ra/Rb; approximately 1.9) were found. Cell membranes responded to luminal Cl removal mostly with a slow hyperpolarization that was mitigated by 8-Br-cAMP or, in some cases, converted into a small, transient depolarization. Our results are best explained by transcellular HCO3 transport in both directions. In secretion, basolateral HCO3 entry occurs by some form of co-transport with Na, and apical exit by Cl/HCO3 exchange. cAMP opens no major electro-diffusive pathway for apical anion efflux. In absorption, HCO3 import from the lumen into the cell is secondary to cAMP-sensitive Na/H exchange.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1990

A nonenzymatic preparation of epithelial basolateral membrane for patch clamp.

A preparation has been developed that permits patch clamping of the basolateral membrane of Necturus gallbladder epithelial cells with a high success rate. The epithelium is separated from the underlying tissues mechanically, without enzymatic treatment. Its apical surface is attached to a plastic cover slip, and the basolateral surface, facing up, is cleaned with a suction pipette under microscopic observation. With this cleaning procedure, the success rate in obtaining gigaohm seals increases from less than 1% to approximately 10% of the attempts. The cells appear to retain their structural and functional integrity, as evidenced by electron-microscopic appearance and magnitude of cell membrane voltages. Major advantages of the preparation are that the basolateral membrane domain is preserved and that enzymatic treatment, which could potentially alter membrane proteins, is not necessary.

Animals↗
PubMed1990

[Importance and function of the melanocyte-stimulating hormone in malignant melanoma. Importance of MSH].

According to the present state of findings there are melanocyte-stimulating hormones (MSH) alpha, beta, gamma and delta with hormone alpha-MSH special physiological importance for man. Our study of special literature shows that the secretion of MSH is affected by exogene factors, different biorhythms and some diseases. Numerous investigation with melanocytes and melanoma cell cultures clearly show the impact of MSH on the function, regulation and the proliferation of pigment cells. The results presented contribute to the discussion of possibilities of improving diagnostics or therapy of malignant melanoma.

Biomarkers, Tumor↗
PubMed1989

Selective blockage of cell membrane K conductance by an antisecretory agent in guinea-pig gallbladder epithelium.

Loperamide inhibits PGE1-induced electrogenic HCO3 secretion in guinea-pig gallbladder. Underlying changes in epithelial cell membrane properties were investigated using intracellular microelectrode techniques in vitro. In the absence of PGE1, mucosal loperamide (10(-4) mol/l) reversibly depolarized both cell membranes by approximately 6 mV. The apparent ratio of membrane resistances (Ra/Rb) remained unchanged and so did voltage responses to luminal Cl removal and Na reduction. The depolarizing response to elevation of luminal K concentration from 5 to 76 mmol/l was decreased from 13 to 8 mV. In the presence of 1 PGE1, the apical membrane is mainly permeable to Cl and HCO3. Under these conditions, loperamide reduced membrane potentials by approximately 10 mV, Ra/Rb remaining constant at approximately 0.4. Effects on voltage responses to changes in luminal Na or K concentration were unchanged. Responses to luminal Cl removal (transient depolarization) were greatly enhanced (from 22 to 42 mV) as predictable from the fall in K permeability that hinders Cl efflux from cell into lumen. Less marked but significant effects were obtained with 10(-5) mol/l (mucosal side) and serosal loperamide (10(-4) mol/l). We suggest that loperamide inhibits electrogenic HCO3 secretion by reducing apical membrane K permeability. The resulting depolarization diminishes the driving force for conductive anion efflux from cell into lumen. This conclusion is supported by the ability of luminal K elevation to mimick loperamide inhibition of the secretory flux of HCO3 (pH-stat experiments).

Animals↗
PubMed1989

Membrane effects of chloride substitutes in guinea pig gallbladder epithelial cells.

Differences in the responses of guinea pig gallbladder epithelial cells to replacement of luminal Cl- with either isethionate (I), gluconate (G), sulfate (S), or cyclamate (C) were investigated in vitro using intracellular microelectrode techniques. In prostaglandin E1 (PGE1)-treated tissues (10(-6) M, serosal side), where electrodiffusive apical membrane Cl- permeability (PCla) is high, replacement of luminal Cl- caused transient membrane depolarizations of similar magnitudes but different times to peak (C greater than G = S greater than I). The subsequent shifts in membrane voltages were, at steady state, straight correlated with the concomitant increases in apparent ratio of apical to basolateral membrane resistances (Ra/Rb). Increases followed the rank order I greater than G = S greater than C, which was also found to be the case in the peak membrane hyperpolarizations on restoring luminal Cl-. Under control conditions (no PGE1, low PCla), three of the substitutes caused a slow hyperpolarization, C greater than G = S, whereas an I-for-Cl- substitution evoked a transient depolarization and a drop in Ra/Rb. Under both control and PGE1 conditions, a transient depolarization followed luminal I-for-C substitution. Our results are best explained by a stimulatory effect of I (and, less marked, G and S) on PCla. Intrinsic effects of cyclamate are not ruled out; however, among the substitutes examined, it is the most inert.

Animals↗
PubMed1989

[The significance of detecting sex hormone receptors for the treatment and prognostic assessment of malignant melanoma].

The current seek for alternative or supplemented therapy is a corner stone in controlled clinical trials and researches concerning malignant melanoma. The discovery of intracytoplasmatic estrogen receptors in the cells of malignant melanoma raised the hope for the use of sexual hormones to perform this therapeutic aspect. In this paper we report on the nature of these sexual hormone receptors, new methodical possibilities, correlations to clinical data together with their significance in diagnosis, therapy and prognosis of malignant melanoma.

Biopsy↗
PubMed1988

Metabolic and nutritional parameters in patients after colonic polypectomy.

Breath methane and hydrogen, plasma acetate, serum selenium, vitamin A and beta-carotene were measured in 47 patients from whom colonic polyps had been removed by endoscopic polypectomy between 3 months and 2 years previously. Patients were compared with 39 control subjects in whom no abnormality was detected during colonoscopy. The proportion of methane exhalers was significantly (p less than 0.0005) higher in patients after polypectomy (66.0%) than in controls (28.2%). Mean plasma acetate was lower (p less than 0.025) in post-polypectomy patients (70.5 microM) than in control subjects (97.1 microM) while breath hydrogen was similar in both groups. The serum concentrations of the antioxidants selenium and beta-carotene showed no differences between the groups whereas vitamin A was higher (p less than 0.01) in serum samples of patients after polypectomy than of controls. These findings indicate that the colonic environment in post-polypectomy patients exhibits certain characteristics which may be related to the formation of benign tumors and possibly colon cancer.

Acetates↗
PubMed1985

Na/H exchange at the apical membrane of guinea-pig gallbladder epithelium: properties and inhibition by cyclic AMP.

The properties and, in particular, the cAMP-sensitivity of apical Na/H exchange in guinea-pig gallbladder epithelium were investigated using gravimetric, pH-stat, and microelectrode techniques. Proton secretion was Na-dependent, inhibited by ouabain and amiloride, and insensitive to changes in apical membrane potential. It was markedly reduced by 8-Br-cAMP and PGE1. PGE1 also attenuated the changes in intracellular Na activity produced by luminal Na removal and restoration. Our results suggest inhibition of Na/H exchange by cAMP. In conjunction with the cAMP-induced rise in apical membrane Cl permeability shown previously, this effect can account for inhibition of NaCl absorption by cAMP.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMedDate not supplied

[Gunshot reconstructions based on individually parametrical 3-dimensional victim models].

In cases of lethal firearm injuries computer enhanced anatomical feasibility studies can provide unambiguous clues concerning self-versus extraneous infliction. To this end individualized digital 3-dimensional geometrical models of the victim and the weapon are generated true to scale with the help of the CAD software (POSER Version 4, egi.sys AG). All anatomical data relevant to the motion apparatus and the range of movement as well as the injuries of the individual victim are carefully documented and serve as input parameters for the digital geometrical model. The bullet path is visualized as a cylinder between entrance and exit wound. A series of simulation sequences then can be carried out by the variation of anatomically possible shot positions and the virtual grasp of the weapon. An exact alignment of the firearm's barrel and the bullet path is a reliable statement for the feasibility of self-infliction. In addition to circumstantial evidence the digital reconstruction of the firearm shot admits of unambiguous conclusions about the course of the traumatic event.

Adult↗
PubMedDate not supplied

[Immunohistochemical insulin evidence at the injection site].

Under suspicion on an injection of high doses of insulin with suicidal or homicidal intention, the local detection of a vital injection of insulin is necessary for the critical examination. The submitted immunohistochemical method shows, that: the insulin-specific positive immunoreaction of the subcutaneous fatty tissue is assigned to an injection of insulin, although a missing staining does not exclude a premortal application of insulin, a widened immunopositive intercellular space between the subcutaneous lipocytes as expression of a local edema points to the intravitality of the injection of insulin.

Adipose Tissue↗