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H Acker

Publications and source records attributed to H Acker.

At least 73 records · Page 4Linked to original sources
PubMed1989

Hypoxic and hypercapnic responses of [Ca2+]o and [K+]o in the cat carotid body in vitro.

Measurements of extracellular Ca2+ and K+ activities [( Ca2+]o, [K+]o) in the superfused cat carotid body in vitro with triple-barrelled ion-selective electrodes have shown that hypoxia induced a decrease in [Ca2+]o of 0.035 +/- 0.17 mM (mean +/- S.D.; n = 17) and a biphasic change in [K+]o which consisted of an increase of 2.3 +/- 1.8 mM followed by an undershoot of -0.52 +/- 0.34 mM (mean +/- S.D.; n = 17). Hypercapnia induced a monophasic upward deflection increase of both [Ca2+]o and [K+]o of about 0.037 +/- 0.013 mM and 0.33 +/- 0.15 mM, respectively (n = 17). During hypoxia, lowering [Ca2+] in the medium to 0.1 mM resulted in a reversed [Ca2+]o response, attenuated [K+]o increase and absence of chemosensory nerve discharges. TTX generally did not affect the hypoxic and hypercapnic induced ionic changes, although the [K+]o undershoot was reduced by 30%. Co2+ competitively blocked the changes in [Ca2+]o and the increase in the sensory nerve discharge elicited by hypoxia and, not competitively, the changes of [K+]o. The ionic changes to hypercapnia were less affected by Co2+. Ouabain inhibited the [K+]o undershoot induced by hypoxia, as did the removal of Na+ from medium. It is concluded that changes in extracellular free Ca2+ and K+ ions concentration induced by hypoxia and hypercapnia represent ionic fluxes related to the transduction process of carotid body cells (glomus and/or sustentacular).

Action Potentials↗
PubMed1989

Influence of ionizing radiation on oxygen profiles in different types of multicellular spheroids.

Human glioma (U-118 MG and U-138 MG), human colorectal adenocarcinoma (HT-29), human thyroid carcinoma (HTh 7), and hamster embryonic lung (V79-379A) spheroids were irradiated with either single doses of 16 or 40 Gy or fractionated doses of eight times 5 Gy. Oxygen profiles in the spheroids were measured with microelectrodes at different times following irradiation, and these profiles were then compared with the oxygen profiles measured in parallel cultured nonirradiated spheroids. No significant radiation-induced changes in the oxygen profiles were seen in any of the spheroids within the first few days after irradiation. The glioma spheroids did not show any significant increase in oxygen tension even after longer times; however, they were growth inhibited, and the number of S-phase cells was strongly suppressed. Increases in oxygen tension did occur in the HT-29 and V79-379A spheroids but only appeared more than a week after irradiation, when degeneration had started. Histological changes and decrease in diameter were seen in the spheroids that started to degenerate about 5 days after irradiation. Thus radiation doses in the therapeutic range did not, for the spheroids studied, produce rapid increases in the oxygen tension. When a change occurred, it appeared rather late and was probably a consequence of cell degeneration.

Adenocarcinoma↗
PubMed1988

Relations between pH, oxygen partial pressure and growth in cultured cell spheroids.

The pH gradients, oxygen partial-pressure gradients and growth curves were measured for 7 different types of spheroids. Growth curves were measured in liquid overlay culture and thereafter the spheroids were attached to cover glasses and transferred to a chamber for micro-electrode measurements. The spheroids were randomly divided for pH or pO2 measurements which then were made under conditions as identical as possible. The decreases in pO2 and pH, delta pO2 and delta pH were calculated as the difference between the values in the culture medium and the values 200 micron inside the spheroids. Each type of spheroid had a certain relation between delta pO2 and delta pH. The human colon carcinoma HT29, the mouse mammary carcinoma EMT6 and the hamster lung V79-379A spheroids had high values of the quotient delta pO2/delta pH. The human thyroid carcinoma HTh7 spheroids and the 3 types of human glioma spheroids had lower quotients. There was a tendency for fast-growing spheroids to have high quotients. Two extreme types of spheroids, HT29 (high quotient) and U-118 MG (low quotient) were analyzed for lactate production and oxygen consumption. The U-118 MG spheroids produced about 3 times more lactate and consumed about 3 times less oxygen than the HT29 spheroids. The differences in lactate production could not be explained by differences in the pyruvate Km values of lactate dehydrogenase. The results indicate that there are significant metabolic differences between the spheroid systems studied.

Animals↗
PubMed1988

Effects of changes in chemoreceptor activity on extracellular K+ and Ca2+ activities in the cat carotid body.

In anaesthetized, paralysed and artificially ventilated cats triple-barrelled ion-selective microelectrodes (ISMs) were inserted into the right carotid body in order to measure extracellular activities of K+ ([K+]o) and Ca2+ ([Ca2+]o) simultaneously. In 3 experiments a method involving iron deposition located the tips of the ISMs in the cellular islands of the organ. A thin cannula inserted into the right carotid artery (i.c.) via the lingual artery was used to infuse Ringer-Locke solutions (0.1-0.5 ml/min) containing either sodium cyanide (NaCN), acetylcholine (ACh) or dopamine (DA). Analysis of the effects of administration of NaCN (20-100 micrograms/min i.c.) showed that during this procedure [K+]o increased and [Ca2+]o decreased by mean values (+/- S.D.) of 0.99 +/- 0.82 and 0.22 +/- 0.06 mM respectively. During administration of ACh (20-50 micrograms/min i.c.) [K+]o increased and [Ca2+]o decreased respectively by mean values (+/- S.D.) of 3.18 +/- 3.0 and 0.31 +/- 0.14 mM. Decreases in [K+]o and [Ca2+]o by mean values (+/- S.D.) of 1.53 +/- 1.64 and 0.34 +/- 0.33 mM respectively were associated with administration of DA (20-50 micrograms/min i.c.). The predominant influences exerted by NaCN and ACh on chemoreceptor activity were excitatory whereas administration of DA caused either inhibition, excitation or a combination of these two effects. Stimulation of the sympathetic supply to the carotid body was associated with either increases, decreases or no reaction of chemosensory activity, [K+]o and [Ca2+]o. The changes in [K+]o associated with the various procedures may reflect the state of polarization within the chemoreceptor complex. Decreases in [Ca2+]o usually accompanied the performance of all procedures and may have resulted from an increased influx of this ion from the interstitial fluids into the cells for the purpose of provoking neurotransmitter release. However, the time course of the changes in [K+]o and [Ca2+]o were considerably slower in onset and recovery than the associated alterations in chemoreceptor activity. Therefore, it is unlikely that these ion changes are directly related to chemoreception but rather represent recovery processes after chemoreceptor modulation. It should be noted that the response times of the ISMs used in this study were too slow to register any rapid changes in [K+]o or [Ca2+]o associated with altered chemoreceptor activity.

Acetylcholine↗
PubMed1988

Primary liver cell cultures grown on gas permeable membrane as source for the collection of primary bile.

Isolated rat hepatocytes maintained in primary culture on gas permeable membrane for 20 h form monolayers and establish at their cell borders a network of canaliculi (approximate diameter 3.5 micron). In the presence of the known choleretic bile acid dehydrocholate, dilation of canaliculi occurs. When nonfluorescent carboxyfluorescein diacetate ester is added to the culture medium, fluorescent carboxyfluorescein appears in the intracanalicular space. In the dilated state, fluid containing the fluorescent compound could be collected from the canaliculi by puncture with a micropipette. The intracanalicular space shows a negative electrical potential difference of 31 mV in reference to the bath solution and is 13.5 mV more positive with reference to recordings from the cytosol of cultured rat hepatocytes. Cultured rat hepatocytes grown on gas permeable membrane are energetically stable over 3 d. On Day 4, ATP levels increase markedly, whereas Na+-K+-ATPase activity declines. Ionic composition of hepatocytes, as measured by electronprobe element analysis on cryosection samples, does not change markedly during monolayer formation. With formation of bile canaliculi, the activity of alkaline phosphatase rapidly increases within 24 h and is stable for the next 3 d. Within that time the activity of gamma-glutamyltranspeptidase, however, increases steadily, reaching a 1.6-fold higher activity than freshly isolated hepatocytes. Bile acids appear in the culture supernatant after 1 d. When unconjugated [14C]cholic acid is added to the cultures the supernatant contains also [14C]tauro- and [14C]glycocholic acid, indicating the preservation of conjugation capacity in these cultures. Total bile acid concentrations in the supernatant increase from 5 to 26 microM on Day 4. The cultures do not secrete alpha-fetoprotein. Monolayer cultures of hepatocytes in the presence of choleretic bile acids seem to be a suitable model system to collect and to analyze the composition of primary bile. In conjunction with the electrical parameters, it is possible to describe directly properties of bile secretion at the canalicular pole of the intact hepatocyte.

Adenine Nucleotides↗
PubMed1987

Influence of glucose and buffer capacity in the culture medium on growth and pH in spheroids of human thyroid carcinoma and human glioma origin.

pH gradients were measured with microelectrodes in cellular spheroids of human glioma (U-118 MG) and thyroid carcinoma (HTh7) origin. pH decreased outside the spheroids and then continuously decreased when the electrode was moved through the spheroid towards the center. The lowest pH values inside the spheroids were in the range 6.7-6.8 when grown under standard conditions with F10 medium. When medium with stronger buffer capacity (Dulbecco's minimum essential medium or Locke's) was used, the gradients in both types of spheroids were less steep. Less steep pH gradients were also obtained in both types of spheroids when the concentration of glucose was lowered to 0.1 g/liter in the medium. In the case of HTh7 spheroids the low pH inside the spheroids under standard culture conditions seemed toxic because the growth rate increased when the spheroids were cultured under conditions giving higher central pH values (high buffer capacity or low glucose concentration). No such growth-stimulating effects could be seen for the U-118 MG spheroids. The growth rate of both types of spheroids was retarded when they were grown in medium with very high glucose concentration (10 g/liter). The thickness of the viable cell layer increased for HTh7 spheroids when the concentration of glucose was lowered to 0.1 g/liter. A decrease in the thickness of the viable layer of U-118 MG spheroids was observed when they were grown at a high glucose concentration (10 g/liter).

Acid-Base Equilibrium↗
PubMed1987

Light absorbance changes in the mouse carotid body during hypoxia and cyanide poisoning.

The isolated carotid body (CB) of the mouse was bathed with modified Tyrode's solution (pO2, 170 Torr) and transilluminated at different wave-lengths (500-620 nm). Difference spectra (normoxia vs hypoxia--pO2, 10 Torr) showed peaks of increased light transmittance (LT) at 500 and especially at 540 and 580 nm. There were troughs of transmittance decrease at 560 and 600 nm. Similar spectra (normoxia vs NaCN 10 mM) revealed increased LT at 500 and 590 nm, whereas there was decreased LT at 550 nm. Therefore, absorbance changes induced by hypoxia and cyanide were different. As as control for residual hemoglobin (Hb) in the tissues, a segment of carotid artery was filled with blood and the same light scanning was performed. The differential signals evoked by hypoxia were much larger. There was some LT increase at 500 and 540 nm, but this effect was especially marked at 570 and 590 nm. NaCN showed the same absorbance pattern, but peaks were of lower amplitude. Thus, the CB-produced signals were not elicited by residual Hb. A stepwise decrease in the medium pO2 (from 170 to 10 Torr) surrounding the CB produced a progressive increase in LT at 540 and 580 nm starting at 120 Torr. A different pattern was evoked by 550 (cytochrome c) and 600 (cytochrome aa3) nm. With 550 nm, transmittance began to increase at about 70 Torr. LT decreased with 600 nm starting at about 120 Torr.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Local flow velocities in the cat carotid body tissue.

With the aid of a new three-dimensional mathematical model local flow velocities in the specific carotid body tissue of the cat measured by hydrogen clearances were calculated to have a mean value of 0.006 cm/s at a perfusion pressure of 50 mm Hg, 0.014 cm/s at a perfusion pressure of 120 mm Hg, and 0.018 cm/s at a perfusion pressure of 170 mm Hg. These results indicate that the carotid body specific tissue possesses a distinct flow heterogeneity with normal capillary flow velocities and a high shunt flow. During hypoxia, the smallest decrease in tissue PO2 was significantly correlated with the highest decrease in flow velocity. This suggests that the carotid body capillary network itself exhibits a PO2 sensor mechanism amplifying the chemoreceptive process in the specific cell elements.

Animals↗
PubMed1986

The norepinephrine and dopamine content of the cat carotid body in vivo under normoxic and hypoxic conditions.

The norepinephrine (NE) and dopamine (DA) content of the cat carotid body (CB) in vivo was investigated under normoxic and hypoxic conditions (5% O2 for 1 h) by radiolabelling method. To avoid a large scattering of the measured values due to inhomogeneity of the biological material, young sib animals were used. The mean NE content under normoxia was 617 +/- 184 pmol/CB, and the mean DA content 451 +/- 200 pmol/CB. Under hypoxia, NE and DA were lowered significantly by 37% and 30%, respectively. From these results we conclude that both transmitters with their known excitatory and inhibitory actions probably influence the chemoreceptive elements in the carotid body.

Animals↗
PubMed1986

Mathematical analysis of tissue PO2 distribution in the cat carotid body.

The PO2 histogram of the carotid body tissue was calculated on the basis of a microscopical serial reconstruction, published physiological data, and a mathematical model. The calculation was made for glomoid as the subunit of the carotid body and the total organ by varying the following parameters: arterial PO2, oxygen consumption, hematocrit, diameter of the vessels, perfusion pressure, and capillary length. The results provide explanations for differences in the literature about the tissue PO2 distribution in the cat carotid body. Differences in the capillary length of the carotid bodies seem to be the main reason for different PO2 histograms. Furthermore, it is shown that the local flow velocities in the carotid body are in the range of local flow velocities known from other organs.

Animals↗
PubMed1985

Extracellular pH changes in the superfused cat carotid body during hypoxia and hypercapnia.

Extracellular pH changes were measured in the superfused cat carotid body with double barreled pH glass microelectrodes, under constant pH (7.45 +/- 0.02), temperature (35 degrees C) and flow (3.6 ml/min) of the superfusion medium. Changes of pO2 in the medium from about 188 Torr (30% O2) to 35 or 12 Torr (5% and 2% respectively) called hypoxia, induced a change of the pH signal of about 0.1 units indicating acidification of the tissue. Medium pH monitored with a pH macroelectrode did not change during hypoxic stimulation. An increase of pCO2 in the medium from about 20 Torr (3% CO2, pH 7.45 +/- 0.02) to 70 Torr (12% CO2, pH 6.98 +/- 0.01) called hypercapnia, under constant pO2 (188 +/- 2 Torr), temperature (35 degrees C) and flow (3.6 ml/min) resulted in acidification of the tissue of about 0.3 pH units. Extracellular pH changes during hypoxia did not occur when the superfusion medium had no glucose; however, pH changes during hypercapnia persisted under these conditions. The hypoxic and hypercapnic chemosensory response of the sinus nerve were decreased or abolished during glucose deprivation in a time-dependent manner. Replacement of glucose with 2-deoxyglucose in the medium led to a similar pattern, i.e. inhibition of the hypoxic and hypercapnic chemosensory nerve response and of the extracellular hypoxic pH changes. These results indicate that glycolysis takes place and contributes to O2 and CO2-chemoreception in the carotid body.

Animals↗
PubMed1985

Redox changes in the mouse carotid body during hypoxia.

The carotid body of the mouse is ideally suited for in vitro photometric and fluorometric studies using transillumination. It is small, thin and translucent. Photometric recordings were made by using a dual wavelength method. Wavelengths of 550 nm (maximal absorbance, MA) and 540 nm (isosbestic point, IP) were employed to study cytochrome c, 600 nm (MA) and 620 nm (IP) for a pigment presumed to be cytochrome aa3, 580 nm (MA) and 570 or 542 nm (IP) to control for possible effects of hemoglobin (Hb). Exposure of the organ to NaCN (10-50 nM) reduced cytochromes c and putative aa3. Hypoxia (produced by superfusing with a medium equilibrated with 100% N2) reduced cytochrome c but tended to oxidize the presumed cytochrome aa3. These effects were apparent at a medium pO2 of 100 torr or less. Fluorometry revealed reduction of NADH under both cyanide exposure and hypoxia. There was little or no interference by Hb when the preparations were carefully washed of remaining red cells. The precise site of the recorded mitochondria is unknown: they could have been located in the parenchymal cells (type I and/or II), nerve terminals, smooth muscle fibers, etc. Resolution of this point will need using dissociated carotid body cells. Further, the possible presence of a special respiratory pigment responding at a wavelength similar to that exciting cytochrome aa3 has not been discarded. Its study would require isolating carotid body mitochondria.

Animals↗