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F Wehner

Publications and source records attributed to F Wehner.

At least 19 recordsLinked to original sources
PubMed1999

Percentile charts to determine the duration of child abuse by chronic malnutrition.

Longstanding quantitative or qualitative under-supply of nutrition leads to weight loss and, in children, to stagnation of growth and thus to stunted growth. A comparison of the expected growth, according to percentile growth curves, with the actual body size, gives an indication as to the period of time in which malnutrition took place. The moment in which the growth curve bends off and leaves the norm is to be interpreted as the earliest begin, the moment in which the attained growth would have been achieved as the latest begin of the nutritional impairment.

Autopsy↗
PubMed1999

Uptake of bromosulfophthalein via SO2-4/OH- exchange increases the K+ conductance of rat hepatocytes.

In confluent primary cultures of rat hepatocytes, micromolar concentrations of bromosulfophthalein (BSP) lead to a sizeable hyperpolarization of membrane voltage. The effect is a saturable function of BSP concentration yielding an apparent value of 226 micromol/l and a Vmax of -10.3 mV. The BSP-induced membrane hyperpolarization is inhibited by the K+ channel blocker Ba2+, and in cable-analysis and ion-substitution experiments it becomes evident that the effect is due to a significant increase in cell membrane K+ conductance. Voltage changes were attenuated by the simultaneous administration of SO2-4, succinate, and cholate (cis-inhibition) and increased after preincubation with SO2-4 and succinate (trans-stimulation), suggesting that the effect occurs via BSP uptake through the known SO2-4/OH- exchanger. Microfluorometric measurements reveal that BSP-induced activation of K+ conductance is not mediated by changes in cell pH, cell Ca2+, or cell volume. It is concluded that K+ channel activation by BSP (as well as by DIDS and indocyanine green) may reflect a physiological mechanism linking the sinusoidal uptake of certain anions to their electrogenic canalicular secretion.

Animals↗
PubMed1998

High-level expression of Na+/D-glucose cotransporter (SGLT1) in a stably transfected Chinese hamster ovary cell line.

The coding region of the high affinity Na+/d-glucose cotransporter (SGLT1) was inserted into the eukaryotic expression vector GFP-N1 under the control of a CMV promoter. The plasmid was then stably transfected into a Chinese hamster ovary cell line (CHO). Transcription and synthesis of SGLT1 were proved by Northern and Western blot analyses. Transport activities of the transfected cells (G6D3) were examined by measuring the sodium-dependent uptake of alpha-methyl[14C]d-glucoside (AMG). Kinetic analysis revealed a Vmax of 10.3 nmol/min/mg (total cell protein) and a Km of 0.26+/-0.09 mM, respectively. The concentration of phlorizin required to inhibit AMG uptake by 50% in the presence of 0.1 mM AMG was 2.35+/-1.84 microM. Electrophysiological studies showed that AMG induces a significant depolarization of membrane voltage in stably transfected CHO cells, suggesting an electrogenic Na-AMG symport. Immunoprecipitation with an antipeptide antibody yielded a nearly homogeneous polypeptide with a molecular mass of about 72 kDa. The amount of SGLT1 present in the CHO cell plasma membranes represents at least 1% of membrane protein, which is about 30-100 times higher than in natural sources, such as renal brush border membranes. In conclusion, the stably transfected G6D3 cells with a markedly high SGLT1 expression can serve as a promising model for studying cellular events related to Na+/d-glucose cotransport and for analyzing the structure and function of the cotransporter itself.

Animals↗
PubMed1998

Insulin- or morphine-injection? Immunohistochemical contribution to the elucidation of a case.

Two autopsy cases of an elderly couple who died on the same day will be used to underline the importance of immunohistochemistry of forensic practice. At first unexplainable injection marks on the upper arms of the corpses and the possibility of a closely related physician injecting insulin and certifying a natural death made it important, considering suspect insulin concentrations in the blood, to exclude insulin injections in these marks. Further, the statement that morphine had been injected for the analgesia of tumour pains, was reinforced by immunohistochemistry.

Aged↗
PubMed1998

Role of Na+ conductance, Na(+)-H+ exchange, and Na(+)-K(+)-2Cl- symport in the regulatory volume increase of rat hepatocytes.

1. In rat hepatocytes under hypertonic stress, the entry of Na+ (which is thereafter exchanged for K+ via Na(+)-K(+)-ATPase) plays the key role in regulatory volume increase (RVI). 2. In the present study, the contributions of Na+ conductance, Na(+)-H+ exchange and Na(+)-K(+)-2Cl- symport to this process were quantified in confluent primary cultures by means of intracellular microelectrodes and cable analysis, microfluorometric determinations of cell pH and buffer capacity, and measurements of frusemide (furosemide)/bumetanide-sensitive 86Rb+ uptake, respectively. Osmolarity was increased from 300 to 400 mosmol l-1 by addition of sucrose. 3. The experiments indicate a relative contribution of approximately 4:1:1 to hypertonicity-induced Na+ entry for the above-mentioned transporters and the overall Na+ yield equalled 51 mmol l-1 (10 min)-1. 4. This Na+ gain is in good agreement with the stimulation of Na+ extrusion via Na(+)-K(+)-ATPase plus the actual increase in cell Na+, namely 55 mmol l-1 (10 min)-1, as we determined on the basis of ouabain-sensitive 86Rb+ uptake and by means of Na(+)-sensitive microelectrodes, respectively. 5. The overall increase in Na+ and K+ activity plus the expected concomitant increase in cell Cl- equalled 68 mmol l-1, which fits well with the increase in osmotic activity expected to occur from an initial cell shrinkage to 87.5% and a RVI to 92.6% of control, namely 53 mosmol l-1. 6. The prominent role of Na+ conductance in the RVI of rat hepatocytes could be confirmed on the basis of the pharmacological profile of this process, which was characterized by means of confocal laser-scanning microscopy.

Animals↗
PubMed1997

Hypertonicity-induced alkalinization of rat hepatocytes is not involved in activation of Na+ conductance or Na+,K+-ATPase.

We investigated whether cell alkalinization via activation of Na+/H+ exchange is involved in the stimulation of Na+ conductance and Na+,K+-ATPase in rat hepatocytes under hypertonic stress. Osmolarity was increased from 300 to 400 mOsm/l at constant extracellular pH (7.4), whereas osmotically induced cell alkalinization (0.3 pH units in HCO3-free solutions) was mimicked by increasing extracellular pH from 7.4 to 7.8 in normosmotic solutions. In intracellular recordings with conventional and ion-sensitive microelectrodes, hypertonic stress led to a transient shift in the voltage response to low Na+ solutions (95% in exchange for choline) by -4.3 +/- 0.8 mV and a continuous increase in cell Na+ from 13.7 +/- 1.8 to 18.6 +/- 3.0 mmol/l within 8 min. In the presence of 10(-5) mol/l amiloride, these effects were reduced by 80 and 90%, respectively. In contrast, increasing pH did not change the voltage responses to low Na+ or cell Na+ concentrations significantly. In addition, application of 2 mmol/l Ba2+ pulses revealed that a sustained membrane hyperpolarization of 15.6 +/- 1.4 mV following intracellular alkalinization exclusively reflects an increase in K+ conductance. Increasing osmolarity at pH 7.4 augmented ouabain-sensitive 86Rb+ uptake from 5.5 +/- 1.1 to 8.5 +/- 1.6 nmol mg protein(-1) min(-1). In normosmotic solution at pH 7.8, 86Rb+ uptake equalled 4.9 +/- 1.6 nmol mg protein(-1) min(-1), which is not significantly different from control. We conclude that, in rat hepatocytes, cell alkalinization under hypertonic stress is not responsible for the activation of Na+ conductance and probably does not participate in the stimulation of Na+,K+-ATPase.

Alkalies↗
PubMed1997

Arachidonic acid as a second messenger for hypotonicity-induced calcium transients in rat IMCD cells.

In rat inner medullary collecting duct (IMCD) cells in primary culture, hypotonic stress induces Ca2+ transients consisting of an early peak phase caused by a Ca2+ release from intracellular stores and a subsequent plateau phase that involves Ca2+ entry from the extracellular milieu. In the present study, the mechanisms by which cell swelling is transduced into the Ca2+ release were investigated. The free intracellular Ca2+ concentration ([Ca2+]i) was measured using the fluorescent dye fura-2 and cell volume using a confocal laser scanning microscope. In control experiments, after reduction of extracellular osmolarity from 600 to 300 mosmol/l, by omission of sucrose, [Ca2+]i rapidly increased from 106 +/- 9 nmol/l to a peak value of 405 +/- 22 nmol/l (P </= 0.05) and thereafter reached a steady-state of 230 +/- 23 nmol/l. In low-Ca2+ conditions (10 nmol/l), the reduction of osmolarity evoked only a transient increase of [Ca2+]i by 182 +/- 11 nmol/l (P </= 0.05), which reflected Ca2+ release from intracellular stores. Hyposmotic stress had no effect on inositol 1,4,5-triphosphate (IP3) production measured by a [3H]IP3 radioreceptor assay. Preincubation with 100 micromol/l ETYA (a non-metabolisible derivative of arachidonic acid) reduced the Ca2+ response to hyposmotic stress under high and low Ca2+ conditions (87 and 85% inhibition respectively) as well as the regulatory volume decrease (RVD). Extracellular application of arachidonic acid in isotonic medium led to an increase in [Ca2+]i under high and low Ca2+ conditions. Pretreatment of IMCD cells with 50 microg/ml D609 (a phosphatidylcholine-directed phospholipase C inhibitor) or with 200 micromol/l propranolol (a phosphatidate phosphohydrolase inhibitor) reduced the hypotonic Ca2+ response more strongly than pretreatment with 5 micromol/l BPhB (a phospholipase A2 inhibitor). The Ca2+ response was also suppressed after preincubation with 200 micromol/l RHC 80267 (a diacylglycerol lipase inhibitor). Preincubation with 50 ng/ml pertussis toxin (a G-protein inhibitor) reduced the transient component of the Ca2+ response partially. We conclude that G-proteins, phosphatidylcholine-directed phospholipase C, phospholipase A2, diacylglycerol lipase and arachidonic acid, but not IP3, are involved in the mechanisms by which Ca2+ is released from the intracellular stores during RVD in IMCD cells.

Animals↗
PubMed1997

Outcome in tall stature. Final height and psychological aspects in 220 patients with and without treatment.

UNLABELLED: In 135 women and 85 men who initially presented for tall stature, the outcome in treated (56 women and 33 men; cases) and untreated (controls) was investigated. At the time of height prediction, cases were significantly taller (P < or = 0.03) than the controls, they had higher target heights (P < 0.001) and adult height predictions (P < 0.001) (according to Bailey and Pinneau) compared to the controls. Bone age (according to Greulich and Pyle) and chronological age were well matched in both groups. Final height was measured after cessation of growth at a mean age above 21.5 years. The final height prediction according to Bailey and Pinneau (BP method) overestimated the final height in controls. The mean error of estimation was -0.14 cm (+/- 3.10) in women, and -1.86 cm (+/- 4.37) in men. Age at the time of prediction did not significantly correlate with the degree of the prediction error. Sex hormone therapy comprised a daily oral dose of 7.5 mg conjugated oestrogens in girls (plus 5 mg dydrogesterone for 10 days a month), while boys received 500 mg testosterone enantate, intramuscularly, every 2 weeks. Therapy was well tolerated. The mean corrected effect of height reducing therapy was 3.6 cm (range: 11.9 cm to -3.3 cm) in women and 4.4 cm (range: 14.2 cm to -5.2 cm) in men. Therapy was significantly more effective when started at an earlier chronological (P < 0.01) and bone age (P < 0.01). The residual mean growth, after therapy was stopped, was 1.8 (+/- 1.6) cm in women and 3.1 (+/- 2.3) cm in men. In men, post-treatment growth was inversely correlated to chronological age (P < 0.01) and bone age (P < 0.05) at the end of treatment, while these correlations were not significant in women. Both groups had a higher educational level than the normal population. Treated tall women reported teasing because of tallness more frequently than controls. In tall men, practical issues such as clothing size predominated. Maximum tolerated height in males was 200 cm and in females 180 cm, thus being nearly analogous to the actual professional criteria for treatment recommendation. A positive attitude to treatment was documented in over 90% of treated individuals. CONCLUSIONS: Our results show that the BP method gives acceptable adult height predictions in girls, but less accurate predictions in boys. The treatment with high doses of sex hormones was low effective in both sexes and showed a wide range of response. For success, treatment must be initiated in early puberty and terminated late. The answers to a questionnaire revealed no major psychological or social maladjustment of treated individuals compared to those untreated.

Adolescent↗
PubMed1996

Osmoregulation in the renal papilla: membranes, messengers and molecules.

This contribution summarizes recent progress in the understanding of the molecular basis of the release of organic osmolytes that occurs when inner medullary cells are confronted with a drop in osmolarity in their environment. For sorbitol release across the basolateral membrane an increase in intracellular calcium seems to be the prominent signal, initiated by G-protein activation, followed by phosphatidylcholine phospholipase activation and generation of arachidonic acid. The increase in betaine permeability is also G-protein dependent but calcium independent, and is restricted to the basal-lateral cell face. Myo-inositol and glycerophosphorylcholine efflux are calcium and G-protein independent and occur both across the apical and basolateral membrane, although to a different extent. Taurine release is also calcium and G-protein independent; a swelling-activated anion channel at the basolateral membrane represents the major efflux pathway.

Animals↗
PubMed1996

Taurine permeation through swelling-activated anion conductance in rat IMCD cells in primary culture.

Whole cell recordings were performed on rat inner medullary collecting duct (IMCD) cells in primary culture. With 140 mmol/l CsCl in bath and pipette we find within 10 min a 60-fold increase in membrane conductance from 0.02 +/- 0.003 to 1.2 +/- 0.1 nS/pF when bath osmolarity is decreased from 600 to 500 mosmol/l. The effect is due to the activation of an outwardly rectifying anion conductance with the anion selectivity SCN- > I- > NO-3 > Br- > Cl- > F- > isethionate > gluconate > or = aspartate > or = glutamate. A relative permeability of the organic osmolyte taurine to Cl- (Ptaurine: PCl-) of 0.15 was detected. With taurine in pipette and bath, the channel exhibits a nearly identical activation and sensitivity profile to a variety of anion channel blockers as under symmetrical Cl- conditions. Furthermore, the 50% inhibitory concentration value for the effect of 5-nitro-2-(3-phenylpropylamino)benzoate on both currents is virtually identical. We conclude that hypotonic stress increases the anion conductance of rat IMCD cells and that this anion conductance mediates taurine efflux.

Animals↗
PubMed1996

Single-channel properties of swelling-activated anion conductance in rat inner medullary collecting duct cells.

Single-channel properties of the volume-activated outwardly rectifying Cl- conductance of rat IMCD cells were studied in primary cultures by means of the patch-clamp technique in the whole cell and in the outside-out configuration. Measurements were performed by noise analysis and in single-channel recordings during voltage-induced current inactivation and reactivation and in long-lasting experiments at constant membrane voltages. Unitary conductances could be defined for the voltage range of -100 to -50 mV and between +50 and +120 mV and chord conductances of 34.1 and 76.6 pS, respectively, can be calculated. The overall current-to-voltage relationship very much resembles that of the macroscopic Cl- conductance and the open probability of the activated channel is close to unity (Po = 0.98-0.99). The channel exhibits many similarities to volume-activated outwardly rectifying Cl- channels found in other systems although certain species differences do exist.

Animals↗
PubMed1995

Activation of a Cl(-)-conductive pathway in primary cultures of rat inner medullary collecting duct (IMCD) cells under hypotonic stress.

In intracellular recordings with conventional microelectrodes on rat IMCD cells, we find that hypotonic stress depolarizes membrane voltage and decreases cell input resistance. Ion substitution experiments reveal that these effects are largely due to the activation of a prominent Cl- conductance. After block of this conductance with dideoxyforskolin a smaller concomitant increase in K+ conductance becomes detectable.

Animals↗
PubMed1995

Hypertonic stress increases the Na+ conductance of rat hepatocytes in primary culture.

We studied the ionic mechanisms underlying the regulatory volume increase of rat hepatocytes in primary culture by use of confocal laser scanning microscopy, conventional and ion-sensitive microelectrodes, cable analysis, microfluorometry, and measurements of 86Rb+ uptake. Increasing osmolarity from 300 to 400 mosm/liter by addition of sucrose decreased cell volumes to 88.6% within 1 min; thereafter, cell volumes increased to 94.1% of control within 10 min, equivalent to a regulatory volume increase (RVI) by 44.5%. This RVI was paralleled by a decrease in cell input resistance and in specific cell membrane resistance to 88 and 60%, respectively. Ion substitution experiments (high K+, low Na+, low Cl-) revealed that these membrane effects are due to an increase in hepatocyte Na+ conductance. During RVI, ouabain-sensitive 86Rb+ uptake was augmented to 141% of control, and cell Na+ and cell K+ increased to 148 and 180%, respectively. The RVI, the increases in Na+ conductance and cell Na+, as well as the activation of Na+/K(+)-ATPase were completely blocked by 10(-5) mol/liter amiloride. At this concentration, amiloride had no effect on osmotically induced cell alkalinization via Na+/H+ exchange. When osmolarity was increased from 220 to 300 mosm/liter (by readdition of sucrose after a preperiod of 15 min in which the cells underwent a regulatory volume decrease, RVD) cell volumes initially decreased to 81.5%; thereafter cell volumes increased to 90.8% of control. This post-RVD-RVI of 55.0% is also mediated by an increase in Na+ conductance. We conclude that rat hepatocytes in confluent primary culture are capable of RVI as well as of post-RVD-RVI. In this system, hypertonic stress leads to a considerable increase in cell membrane Na+ conductance. In concert with conductive Na+ influx, cell K+ is then increased via activation of Na+/K(+)-ATPase. An additional role of Na+/H+ exchange in the volume regulation of rat hepatocytes remains to be defined.

Animals↗
PubMed1994

Intracellular Ca2+ release and Ca2+ influx during regulatory volume decrease in IMCD cells.

Volume changes and cytosolic Ca2+ concentration ([Ca2+]i) of inner medullary collecting duct (IMCD) cells under hypotonic stress were monitored by means of confocal laser scanning microscopy and fura 2 fluorescence, respectively. Reduction of extracellular osmolality from 600 to 300 mosmol/kgH2O by omission of sucrose led to an increase in cell volume within 1 min to 135 +/- 3% (n = 9), followed by a partial regulatory volume decrease (RVD) to 109 +/- 2% (n = 9) within the ensuring 5 min. In parallel, [Ca2+]i rose from 145 +/- 9 to 433 +/- 16 nmol/l (n = 9) and thereafter reached a lower steady state of 259 +/- 9 nmol/l. Under low-Ca2+ conditions (10 nmol/l) RVD was not impeded and reduction of osmolality evoked only a transient increase of [Ca2+]i by 182 +/- 22 nmol/l (n = 6). Preincubation with 100 mumol/l 8-(N,N-diethylamino)octyl-3,4,5-trimethoxy-benzoate hydrochloride (TMB-8) or 20 mmol/l caffeine, both effective inhibitors of Ca2+ release from intracellular stores, in low Ca2+ as well as in high Ca2+, inhibited the Ca2+ response and abolished RVD. The temporal relationship between Ca2+ release from intracellular stores and Ca2+ entry was analyzed by determining fura 2 quenching, using Mn2+ as a substitute for external Ca2+. Intracellular Ca2+ release preceded Mn2+ influx by 17 +/- 3 s (n = 10). Mn2+ influx persisted during the whole period of exposure to hypotonicity, indicating that there is no time-dependent Ca2+ channel inactivation. Preincubation with TMB-8 or caffeine reduced Mn2+ influx to the control level, indicating that activation of Ca2+ channels in the plasma membrane occurs via intracellular Ca2+ release.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Electron probe X-ray microanalysis of epithelial cells: aspects of cryofixation.

Content and distribution of diffusible ions in epithelial cells were studied by scanning transmission electron microscopy and energy dispersive electron probe X-ray microanalysis of freeze-dried cryosections from trout kidney, rat liver and Malpighian tubules of Drosophila larvae. Cryofixation of small excised kidney and liver samples by rapid immersion into liquid propane resulted in intracellular K/Na-ratios < 1. In contrast, K/Na-ratios > 7 were obtained after in situ cryofixation by means of a cryopunching device which allows tissue pieces to be frozen during excision from the intact organ. Isolated hepatocytes cryofixed in a small droplet of culture medium had a K/Na-ratio of 3.7. After culturing the hepatocytes, the K/Na-ratio increased to 24. Effects of extracellular media of different composition on the intracellular element content were studied. Malpighian tubules of Drosophila larvae were cryofixed by rapid immersion into liquid propane, and the distribution of K across the cells forming the tubules from the basal to the apical cell membrane was measured. An increasing K gradient was found from the intermediate to the apical cytoplasm. The intracellular K distribution was dependent on ions and transport inhibitors present in the fluid surrounding the Malpighian tubules within the larvae. Content and distribution of ions in epithelial cells sensitively depend on the physiological state immediately before cryofixation. Thus, electron probe X-ray microanalysis of cells and cell functions requires careful selection and control of the cell system to be studied.

Animals↗
PubMed1993

Taurocholate depolarizes rat hepatocytes in primary culture by increasing cell membrane Na+ conductance.

Rat hepatocytes in primary culture were impaled with conventional microelectrodes. Addition of 5-100 mumol/l taurocholate led to a slowly developing depolarization that was maximal at 50 mumol/l (10.5 +/- 1.5 mV, n = 15) and not reversible. The effect was Na+ dependent and decreased in cells preincubated with 1 mumol/l taurocholate. Increasing external K+ tenfold depolarized the cells by 12.3 +/- 2.3 mV under control conditions and by 6.3 +/- 1.2 mV with 50 mumol/l taurocholate present (n = 7). Depolarization by 1 mmol/l Ba2+ was 7.6 +/- 0.8 mV and 6.0 +/- 0.7 mV (n = 9) before and after addition of taurocholate, respectively. Cable analysis and Na+ substitution experiments reveal that this apparent decrease in K+ conductance reflects an actual increase in Na+ conductance: in the presence of taurocholate, specific cell membrane resistance decreased from 2.8 to 2.3 k omega x cm2 x Na+ substitution by 95% depolarized cell membranes by 8.9 +/- 2.9 mV (n = 9), probably due to indirect effects on K+ conductance via changes in cell pH. With taurocholate present, the same manoeuvre changed membrane voltages by -0.8 +/- 2.6 mV. When Na+ concentration was restored to 100% from solutions containing 5% Na+, cells hyperpolarized by 3.5 +/- 3.6 mV (n = 7) under control conditions and depolarized by 4.4 +/- 2.9 mV in the presence of taurocholate, respectively. In Cl- substitution experiments, there was no evidence for changes in Cl- conductance by taurocholate. These results show that taurocholate-induced membrane depolarization is due to an increase in Na+ conductance probably via uptake of the bile acid.

Animals↗