Biomedical subjects

G M Roomans

Publications and source records attributed to G M Roomans.

At least 55 records · Page 3Linked to original sources

PubMed1999

Effects of pituitary adenylate cyclase activating polypeptide-27 (PACAP) and vasoactive intestinal polypeptide (VIP) on chloride in HT29 cells studied by X-ray microanalysis.

The colon cancer cell line HT29 is a useful model to study intestinal chloride secretion. These cells have both cAMP-activated and calcium-activated chloride channels. Changes in elemental content of the cells after stimulation with agonists were determined by X-ray microanalysis in the scanning or scanning transmission electron microscope. Exposure of HT29 cells to pituitary adenylate cyclase activating polypeptide-27 (PACAP) caused a transient decrease in the cellular Cl and K concentrations, indicating (net) efflux of chloride. The effect of PACAP is inhibited by somatostatin, which is known to inhibit cAMP-activated as well as calcium-activated chloride secretion and by U-73122, an inhibitor of phospholipase C. Alloxan, an inhibitor of adenylate cyclase, did not significantly affect the PACAP-induced loss of chloride. The calcium-chelating agent EGTA inhibited the PACAP-induced loss of chloride, indicating the need for extracellular calcium ions. Also vasointestinal polypeptide (VIP) caused a decrease of the cellular chloride concentration in HT29 cells. VIP-induced loss of chloride could be inhibited by pre-treating the cells with somatostatin or UK14,304, an alpha-2 adrenergic agonist that has been shown previously to inhibit purinergically activated chloride efflux. Our results indicate that there is cross-talk between the cAMP- and the calcium-activated pathways for chloride secretion in HT29 cells.

Adenylate Cyclase Toxin↗

PubMed1999

Effects of UTP on Na+, Cl- and K+ transport in primary cultures from human sweat gland coils.

Extracellular ATP and UTP can increase membrane permeability in the sweat gland, but the intracellular signalling regulating the response to these agonists is poorly understood. Stimulation of Cl- transport by nucleotides has been suggested as a pharmacological therapy to improve Cl- secretion in patients with cystic fibrosis. In the present study, regulation of Na+, Cl- and K+ transport in primary cultures of cells from the secretory coil of human sweat glands was investigated by electron probe X-ray microanalysis. Stimulation with 200 microM UTP for 2 min at room temperature caused a significant increase in intracellular Na but did not affect Cl and K. After 5 min, the Na concentration was still increased, but now also a significant decrease in Cl and K was observed, indicating an increase in Cl- and K+ permeability. The effect of UTP on Cl- secretion was enhanced in Mg2+-deficient buffer, indicating that the response is elicited by the extracellular fully ionized form of UTP (UTP4+), but not by MgUTP2+. The effects of UTP were abolished in Ca2+-deficient buffer supplemented with EGTA. Alloxan, an adenylate cyclase inhibitor, did not inhibit the response to UTP. These results indicate that the membrane Cl- and K+ permeability elicited by UTP in primary coil cell cultures is Ca2+-dependent. The response to UTP did not attenuate at 8 degrees C, suggesting that it could be activated, in part, via ligand-gated ion channels. The effect of UTP was not decreased in the presence of ouabain. Pre-treatment of the cells with pertussis toxin (24 h) had minor effects on Cl- secretion activated by UTP, indicating a role for G proteins in the UTP activation of Cl- secretion.

Adenylate Cyclase Toxin↗

PubMed1999

Retaining ionic concentrations during in vitro storage of tissue for microanalytical studies.

When human or animal tissue is to be investigated by X-ray microanalysis, it is sometimes necessary to store the tissue between removal from the organism and freezing. However, when excised tissue is stored in buffer, the elemental concentrations in the cell may change. In the present study, it was attempted to develop a storage buffer that would retain the cellular elemental concentrations close to their in situ values. To start, the NaCl component in Krebs-Ringer buffer was exchanged for K-gluconate and KCl for NaCl. This buffer was called a '100% high K+ solution'. Starting from this solution, part of the K-gluconate was replaced by an equivalent amount of NaCl. Incubation of excised rat liver (4 degrees C, 4 h) in 85% high K+ solution resulted in retention of cellular Na, K, Ca, S and Mg concentration most closely to the in situ state, whereas cellular Cl was retained best when the tissue was incubated in 75% high K+ solution. For rat submandibular gland, incubation in 80% high K+ solution resulted in optimal retention of cellular Na, K, Ca, P, S and Mg, while Cl was retained best in a 70% high K+ solution. Based on these results, an optimally modified Krebs-Ringer solution for the liver would consist of 119 mM K+, 26 mM Na+ and 45 mM Cl-. An optimally modified Krebs-Ringer bicarbonate solution for the submandibular gland would be composed of 96 mM K+, 53 mM Na+ and 46 mM Cl-. After incubation in the modified solutions (at 4 degrees C), cellular Na, Mg, S, Cl, K and Ca in both tissues were maintained close to the in situ state throughout a 6-h incubation. The cellular P concentration was reduced after incubation for 1 h; thereafter, in the liver cells it remained at this lower level for the rest of the incubation, whereas in the submandibular gland tissue it increased again after 4 h. The increase in cell volume (oedema) was less in tissue stored in the modified solutions, than in the 100% high K+ solutions. Incubation in high Na+ buffers (4 degrees C, 6 h) resulted in a progressive increase in the percentage of cells showing trypan blue uptake. A similar increase in trypan blue uptake was seen in the modified solution, but this increase levelled off after 4 h. After cholinergic stimulation in high Na+ solution (25 degrees C, 1 min), the expected decrease in cellular Cl concentration was seen in submandibular gland cells that had previously been preserved (4 degrees C, 4 h) in the modified solution, but not in those that had been preserved in the 100% high K+ solution.

Animals↗

PubMed1999

Multiple intracellular pathways for regulation of chloride secretion in cultured pig tracheal submucosal gland cells.

Tracheal submucosal glands are of great relative importance in the secretion of chloride and water to the airway lumen. This study aimed to examine whether the cystic fibrosis transmembrane conductance regulator (CFTR) is involved in cyclic adenosine monophosphate (cAMP) or Ca2+-activated Cl- secretion. Regulation of Cl- secretion in cell cultures derived from pig tracheal submucosal gland acini was investigated by X-ray microanalysis. With or without preincubation with CFTR antisense oligodeoxynucleotide (5 microM). A significant decrease in cellular Cl and K concentration was induced by 5 mM 8-bromo-adenosine 3': 5'-cyclic monophosphate (8-bromo-cAMP), 3 microM calcium ionophore ionomycin, 200 microM 5'-uridine triphosphate (UTP) and 200 microM 5'-adenosine triphosphate (ATP), respectively. The decrease in cellular Cl content was significantly inhibited by the Cl- channel blocker 5-nitro-2-(3-phenylpropyl-amino)-benzoic acid (NPPB; 50 microm). Preincubation of the cells with CFTR antisense oligodeoxynucleotide significantly inhibited the 8-bromo-cAMP-induced decrease in Cl, whereas CFTR sense oligodeoxynucleotide had no effect. The effects of ionomycin, ATP or UTP were not blocked by either CFTR antisense oligodeoxynucleotide or CFTR sense oligodeoxynueleotide. To measure the cytosolic free calcium concentration ([Ca2+]i) the cells grown on glass coverslips were loaded with fura-2 tetraoxymethylester (fura-2 AM; 5 microM). The [Ca2+]i was measured as the fluorescence ratio of emission (340/380 nm). Ionomycin (3 microM) caused a rapid increase in [Ca2+]i followed by a sustained plateau, but 8-bromo-cAMP had a more complex effect on [Ca2+]i. Exposure to ATP or UTP caused a rapid increase in [Ca2+]i followed by a decrease. In conclusion, cystic adenosine monophosphate and ionomycin induced Cl- secretion through different intracellular pathways. Adenosine triphosphate and uridine triphosphate also induced Cl- secretion probably with Ca as an intracellular messenger. The cystic fibrosis transmembrane conductance regulator is not involved in Cl- secretion activated by extracellular adenosine triphosphate and uridine triphosphate.

Adenosine Triphosphate↗

PubMed1998

Volume-induced chloride transport in HT29 cells studied by X-ray microanalysis.

Ion transport mediated by osmotically induced chloride channels in HT29 cells was investigated by X-ray microanalysis of cell cultures. The cells were cultured on cellulose nitrate filters, and exposed to isotonic, hypotonic, or hypertonic solutions. Then the NaCl-rich medium was removed by rinsing the cells with a washing fluid, the cells were frozen, freeze-dried, and analyzed. As washing solutions, distilled water, ammonium acetate, or mannitol (the latter two at different concentrations) were used. No major effects of the composition of the washing fluid was noted, except for mannitol, which left remnants that caused an apparent decrease in the intracellular elemental concentrations. In response to exposure to hypotonic solution (modified Krebs Ringer's buffer, KRB, with 90 mM NaCl), the cells lost Cl, K, and Na. On the other hand, exposure to hypertonic solution (modified KRB, 290 mM NaCl) caused an increase of the intracellular concentrations of Na and Cl and a decrease in K. In the presence of chloride channel blockers, chloride efflux induced by exposure to hypotonic medium was inhibited. This chloride efflux was also inhibited in the absence of extracellular calcium, indicating that the process is Ca2+ dependent.

Cell Size↗

PubMed1998

Identification of two further gap-junctional proteins, connexin40 and connexin45, in human myometrial smooth muscle cells at term.

The powerful synchronous contractions of the uterus in labor depend on electrical coupling of myometrial smooth muscle cells by gap junctions. In humans and other mammals, gap junctions are scarce in the myometrium of the non-pregnant uterus, but become abundant at term and/or with the onset of labor. Previous work has shown that the gap-junctional protein (connexin) expressed by human myometrial smooth muscle cells is connexin43, the same connexin type that predominates in cardiac muscle. Here we show that two further gap junctional proteins, connexin40 and connexin45, are expressed by the myometrial smooth muscle cells of the human uterus at term. Transcripts encoding the human isoforms of these connexins were demonstrated by Northern blot analysis, and immunoconfocal microscopy enabled precise localization of the corresponding proteins to punctate contact points (i.e., gap junctions) between interacting smooth muscle cells. Double labeling demonstrated that, while some fluorescent spots comprise only connexin43, both connexin40 and connexin45 predominantly colocalize to connexin43-positive fluorescent spots. Triple labeling revealed that where all three connexin types were expressed, they frequently localized to the same gap junction spot. As gap-junctional channels composed of different connexin types have been demonstrated in vitro to have different functional properties, multiple connexin expression may contribute to modulation of gap junction function in human myometrial smooth muscle cells in vivo.

Blotting, Northern↗

PubMed1998

X-ray microanalysis of in situ and isolated pancreatic islets.

The effect of stimulation of insulin secretion in pancreatic beta cells on the elemental composition of these cells was investigated by x-ray microanalysis. In vitro experiments on isolated islets of Langerhans from ob/ob mice were compared to in situ experiments. The only significant difference in the elemental composition of beta cells from ob/ob mice versus their lean counterparts is a lower Ca concentration in the ob/ob animals. The nucleus of the beta cells has a higher concentration of P, K, and Na than the cytoplasm, which has a higher concentration of S and Cl. No polarized ion distribution in the cytoplasm of the beta cells was observed. Isolated beta cells show a higher concentration of Na and Cl and a lower concentration of K than their in situ counterparts. Stimulation of insulin secretion with glucose both in situ and in vitro showed only very small effects on the elemental composition of the beta cells: a tendency to a decreased P content was noted. In vitro experiments using stimulation with high extracellular K+ showed, in addition, a small increase in the intracellular K concentration. In conclusion, while the elemental content of beta cells in vitro differs from that in situ, the response to glucose stimulation appears to be similar in both systems.

Animals↗

PubMed1998

Regulation of ion content in primary cultures from reabsorptive ducts of human sweat glands studied by X-ray microanalysis.

X-ray microanalysis was used to investigate whether cAMP- and/or Ca2+-activated regulation of chloride and potassium efflux is expressed in primary cultures of sweat gland duct cells. The effects of extracellular UTP and ATP on the duct cells, and the signalling system involved in the response to ATP was also studied. Primary cultures from duct cells of human sweat glands responded to 1 microM carbachol, 2 microM of the Ca2+ ionophore A23187, or 5 mM 8-bromo-cAMP stimulation for 5 min, resulting in a decrease in cellular Cl and K concentrations. 50 microM 5-nitro-2-(3-phenylpropyl-amino)-benzoic acid (NPPB), a Cl- channel blocker, can inhibit the decrease in Cl concentration induced by cAMP. Extracellular (200 microM) ATP caused a decrease of Cl and K in cultured duct cells, while (200 microM and 2 mM) UTP was ineffective. Both the phosphoinositidase C inhibitor U73122 (10 microM) and the absence of extracellular Ca2+ abolished the ATP-induced decrease in Cl and K content. Alloxan (1.25 mM), an adenylate cyclase inhibitor, had an inhibitory effect on the response to ATP. The decrease in K, but not in Cl, content in the cells elicited by ATP was blocked by prior incubation with 100 ng/ml pertussis toxin, indicating the coupling of ATP to pertussis toxin-sensitive G-proteins. In conclusion, both Ca2+- and cAMP-dependent Cl- permeability is present in primary cultures from duct cells of human sweat gland. The response to ATP can be mediated both by Ca2+- and by cAMP-dependent pathways, and is coupled to pertussis toxin-sensitive G-proteins.

Adenosine Triphosphate↗

PubMed1998

Chloride transport in a human submandibular gland cell line studied by X-ray microanalysis.

Ion transport properties of the human submandibular gland cell line A253 were investigated by X-ray microanalysis. The cells were grown on ultrathin plastic films on titanium grids. After the experiment, where the cells were exposed to various agonists and inhibitors, the specimens were briefly rinsed in distilled water, frozen, and freeze-dried. The elemental composition of the cultured cells most closely resembled that of striated duct cells. Beta-adrenergic stimulation caused a small decrease in the cellular Cl- and K+ concentration, but cholinergic stimulation had no effect. Also stimulation with cAMP caused a decrease in Cl- and K+; this decrease could be inhibited by the chloride channel blocker NPPB. Loss of Cl- and K+ could also be elicited by exposure to a hypotonic solution. The results suggest that there may be several types of chloride channel present in A253 cells.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1998

Storage of trachea for X-ray microanalytical studies of tracheal submucosal glands.

Pig trachea is a good model system to study airway fluid transport with relevance to human diseases such as cystic fibrosis, since both in pig and in man, the submucosal glands play a quantitatively important role in fluid secretion. Pig trachea can be easily obtained from the local slaughterhouse. In the present study, we investigated the procedure to transport the tissue from the slaughterhouse to the laboratory where physiological experiments can be carried out. Transport of the tissue in a solution with high K+ content (resembling the intracellular environment) maintained the morphology of the glands and a high intracellular K/Na ratio. Physiological experiments can be carried out in solutions with a high Na+ concentration resembling the extracellular environment. The glands secrete chloride on stimulation with alpha-adrenergic, beta-adrenergic, cholinergic and peptidergic agonists. Transport and temporary storage of tissue in high K+ solutions expands the scope of possible X-ray microanalytical studies in the field of pathophysiology.

Animals↗

PubMed1998

Effects of nicotine administration on elemental concentrations in mouse granulosa cells, maturing oocytes and oviduct epithelium studied by X-ray microanalysis.

A normal maturation of the oocytes is dependent upon, among other things, normally functioning granulosa and corona radiata cells. Analyses performed during human in vitro fertilization programs have revealed that, in smokers, ovarian functions are affected and that smokers have a decreased fertilization rate. Further, animal studies have indicated that nicotine can reach the genital tractus, and that nicotine administration interferes with oocyte maturation, fertilization and early pregnancy. We applied X-ray microanalysis to monitor whether nicotine administration changed the ionic balance of cells in the reproductive tract (granulosa cells, oocytes and oviduct epithelial cells). The animals were given nicotine in the drinking water at a concentration of 108 mumol/l. After 15 days the animals were superovulated, ovaries and oviducts were frozen, and thick cryosections were prepared for energy-dispersive X-ray microanalysis. In the granulosa cells, the concentrations of Na and Cl increased after nicotine treatment, while the K concentrations decreased resulting in an increased Na/K ratio. The treated oocytes had a higher K concentration and a decreased Na/K ratio compared to the controls. In the epithelial cells of the oviduct, the concentrations of Na and K decreased after nicotine treatment without any changes in the Na/K ratio. Thus, heavy nicotine administration to mice causes significant changes in the ionic composition of the granulosa cells, the ovarian oocytes and the oviduct epithelium.

Animals↗

PubMed1997

Aspects on the physiology of human skin: studies using particle probe analysis.

The cellular part of the skin, the epidermis, is a very thin structure, approximately 120 microns thick, a fact which has hindered the exploration of the physiology of the epidermis in normal and pathological conditions. An additional complication is the fact that the epidermis contains layers of cells at different stages of differentiation. Therefore, conventional physiological capillary probes cannot, with any satisfactory precision, be located within a specified cell of a specified layer of the skin in vivo. Hence, alternative ways for the exploration of skin physiology have been sought for. In the past, analysis of the elemental content of skin was done was done as bulk measurements, and surprisingly wide ranges of elemental content were recorded. The width of these ranges was most certainly due to the sampling methods used rather than the sensitivity of the chosen method of analysis. Also, these older measurements did not discriminate between the different strata, and therefore the information provided little if any substance for a functional analysis of processes involved in normal and pathological differentiation of the epidermis. Particle probes, however, have been able to overcome such methodological problems. Over a period of 15 years we have studied normal human skin, normal-looking, paralesional skin from psoriatics, and skin from persons suffering from atopic dermatitis using PIXE analysis. In recent years, trace elements have been shown to work as secondary messengers or regulatory substances. As an example, calcium (Ca2+) has proven to be a very important signalling substance in a great variety of cellular systems. Studies with the transmission electron microscope (TEM) as well as histochemical methods have allowed an understanding of the role of Ca2+ in the differentiation process of the epidermis. Ca2+ has also been shown to play an important role in apoptosis (programmed cell death), which is currently a hot subject for the obvious reason that the final differentiation step between the stratum granulosum level and the stratum corneum represents a particular aspect of programmed cell death. The importance of the balance between calcium and zinc in apoptosis has been clearly demonstrated in a number of cellular systems, but we have still to clarify the validity of topical treatment with Zn ointments in different skin conditions. Substantial iron (Fe) losses via psoriatic lesions were demonstrated more than two decades ago, and these data were given new meaning when we found that a more discrete loss occurs in clinically normal-looking psoriatic skin. Obviously, such findings stress the importance of understanding the relation between the elemental content and normal and abnormal physiology. The ultimate goal of particle probe studies is to provide an understanding of the formation of a mature stratum corneum with a functional barrier reflected in physiological/biochemical mechanisms behind the properties of changed skin in patients afflicted with skin disorders of genetic or constitutional origin. This paper aims to give an overview of the state of the art in skin physiology made possible through the use of particle probes.

Animals↗

PubMed1997

Regulation of ion transport by P2u purinoceptors and alpha 2A adrenoceptors in HT29 cells.

X-ray microanalysis was applied to investigate ion transport mediated by P2U purinoceptors and alpha 2A adrenoceptors as well as their interaction in the regulation of the intracellular elemental concentration in HT29 cells. In response to ATP, HT29 cells showed a decrease of intracellular Cl, Na and an increase in Ca. A similar result was observed with UTP, but UTP appeared to be more potent than ATP. On the other hand, UK14,304, an alpha 2 receptor agonist, was found to be capable of reversing the action of both UTP and ATP on ion secretion, and caused a clear increase in intracellular Na and Cl. Moreover, treatment of cells with UK14,304 before exposure to UTP did not induce a decrease in Cl and Na, suggesting that UK14,304 blocks the action of UTP. The secretory effect of UTP was also blocked by NPPB, a chloride channel blocker, and alloxan. Chelation of extracellular Ca with EGTA abolished ion response to UTP. These results suggest that since inhibition of the intracellular cAMP system and chelation of Ca2+ can block the nucleotide-induced chloride secretion, the ATP and UTP-induced chloride secretion can be mediated via both cAMP-dependent and Ca(2+)-dependent pathways.

HT29 Cells↗

PubMed1997

Human neutrophil lipocalin (HNL) is a specific granule constituent of the neutrophil granulocyte. Studies in bronchial and lung parenchymal tissue and peripheral blood cells.

The neutrophilic granulocyte is a cytotoxic and potentially tissue-injuring cell participating in the destructive processes and symptoms seen in a variety of inflammatory diseases. Sensitive immunoassays have been introduced to measure the levels of specific secretory proteins of various inflammatory cells in blood and other body fluids. The aim has been to develop highly specific markers for each cell type. The results obtained by immunoassay have indicated that human neutrophil lipocalin (HNL) is a protein unique to the neutrophil. The present study investigated the specificity of HNL as a neutrophil marker in peripheral blood and lung tissue by using flow cytometry and immunocytochemistry. Flow cytometry and immunocytochemistry on peripheral blood showed that monoclonal antibodies to HNL only react with neutrophils and not with other types of leukocytes. Immunocytochemistry on plastic-embedded sections and on frozen sections of lung tissue showed that a cocktail of six monoclonal antibodies to HNL specifically reacts with neutrophils and not with epithelial cells or macrophages. By immunoelectron microscopical studies performed on healthy human neutrophils after low temperature embedding in Lowicryl K4M following aldehyde fixation and partial dehydration, it could be shown that HNL colocalized with lactoferrin (a known marker for secondary or specific granules) and that myeloperoxidase was localized in the primary or azurophil granules. The results confirm that HNL is a unique component of the secondary granules of the neutrophil granulocyte.

Acute-Phase Proteins↗

PubMed1997

Effects of cholinergic and alpha-adrenergic agonists on the monovalent ion content of rat submandibular gland acinar cells studied by X-ray microanalysis.

The effects of cholinergic and alpha-adrenergic stimulation (in vivo and in vitro) on the monovalent ion content of rat submandibular gland acinar cells were evaluated at the subcellular level by X-ray microanalysis. Fragments of glands or enzymatically dispersed acini were slam-frozen and cut into ultrathin cryosections. Spectra were collected from secretory granules, nucleus, the basal cytoplasm containing endoplasmic reticulum and the apical cytoplasm identified between secretory granules. No significant changes in Na and Cl content were observed after the isolation of acini, but the K concentration decreased compared with cells from in situ glands. The Cl and K content in all four compartments studied decreased significantly after cholinergic stimulation both in vivo and in vitro but in a more restricted fashion after alpha-adrenergic stimulation. Our findings indicate that: (1) the physiological mechanisms regulating the monovalent ion composition of submandibular cells are relatively well preserved in isolated acinar cells; (2) the results from in vivo experiments are in good agreement with those from in vitro experiments; and (3) the effects of cholinergic and alpha-adrenergic stimulation on the K+ and Cl- efflux at the subcellular level are similar but the response is generally less with alpha-adrenergic stimulation.

Adrenergic alpha-Agonists↗

PubMed1997

Use of low temperature and high K+ incubation media for in vitro tissue preparation for X-ray microanalysis.

Incubation of tissue slices in physiological buffers gives rise to significant changes in the intracellular ion concentrations, which may disturb subsequent X-ray microanalysis. In the present study it was attempted to design incubation conditions that retain the in vivo conditions better. The following variables were investigated: (1) exchange of Na+ in the incubation medium for K+, and exchange of Cl- for the less permeable gluconate anion; (2) incubation at 4 degrees C rather than at 37 degrees C; and (3) addition of dextran to the incubation medium. Brief exposure (a few seconds) of liver slices to a buffer causes changes in the intracellular Na, Cl and K concentrations, depending on the ionic composition of the buffer. Incubation in a normal physiological (high NaCl) buffer at 37 degrees C results in a further increase of Na and Cl and a further decrease in K in liver cells. The changes reach a maximum at 30 min and the concentrations then remain stable throughout a 2-h incubation. Incubation in sodium gluconate medium or addition of dextran to the physiological buffer somewhat reduces the changes in the intracellular ion composition (compared to the standard physiological incubation medium). Incubation in potassium gluconate medium results in a decrease in cellular Na and an increase in K. Quantitative morphological studies show that tissue oedema is observed to the same extent in hepatocytes incubated in sodium gluconate, potassium gluconate and physiological buffer containing 10% dextran. However, these buffers cause significantly less cell oedema than the physiological (high NaCl) buffer. Incubation of liver, cerebral cortex or submandibular gland slices in physiological (high NaCl) solutions at 4 degrees C for 4 h caused a more extensive increase in Na+ and decrease in K+ than incubation at 37 degrees C for 2 h. This suggests inhibition of the Na+, K(+)-ATPase under these conditions. As compared to incubation at 37 degrees C for 2 h, tissues incubated in potassium gluconate buffer at 4 degrees C for 4 h have a cellular K concentration closer to the in situ value. Cholinergic stimulation of tissue slices from cerebral cortex and submandibular gland at room temperature for 1 min shows the best physiological response in tissue slices preincubated at 4 degrees for 4 h in high KCl, potassium gluconate and high NaCl, in this order. The response can, however, only be seen, when cholinergic stimulation is carried out in a standard physiological buffer with a high NaCl concentration. It is concluded that in vitro storage of tissue for X-ray microanalysis is best carried out at 4 degrees C in a solution with a high K+ concentration.

Absorption↗

PubMed1997

Dry gas hyperpnea changes airway reactivity and ion content of rabbit tracheal wall.

Dry air hyperventilation provokes airway narrowing in asthmatics. The mechanism is thought to involve the release of inflammatory mediators in response to airway osmolarity. The response to inhaled histamine on lung mechanics and the ion content of the airway subepithelial connective tissue after dry gas hyperventilation was investigated in rabbits. Resistance increased more after histamine given after hyperventilation with dry gas compared to humid gas (P < 0.05). Compliance decreased after histamine for both dry and humid gas hyperventilation. The Na, Cl and K content was decreased in the tissue at 4 min (P < 0.001) and nearly returned to resting content at 8 min of hyperventilation with dry gas. The results suggest that dehydration occurred and was followed by oedema formation in the tracheal wall. Thus, the effects of inhaled histamine on airway resistance was amplified. The mechanism involved may be part of the normal defence of the airway to protect against desiccation during hyperventilation with dry air. This response may be exaggerated in asthmatics.

Airway Resistance↗

PubMed1997

X-ray microanalysis of uterine epithelial cells in culture.

The ionic composition of the uterine fluid, secreted by the endometrium, is of importance for fertilization and embryonic development. Little, however, is known about the ion transport mechanisms in the uterine epithelial cells. Because it is difficult to study ion transport in this tissue in situ, a method was developed to culture mouse uterine epithelial cells for X-ray microanalysis in the electron microscope, in order to allow the study of ion transport. Our data suggest the presence of a number of ion transport mechanisms in the cultured uterine epithelial cells. The cells appear to possess a ouabain-sensitive Na(+)-K(+)-ATPase, an amiloride-sensitive Na(+)-H+ antiporter, cAMP- and Ca(2+)-activated chloride channels, and volume-activated chloride efflux and influx mechanisms. In addition, chloride efflux can be stimulated by cholinergic and alpha-adrenergic agonists. Only a few of these mechanisms had been studied previously in the uterine epithelium.

Acetylcholine↗