Biomedical subjects

M Fromm

Publications and source records attributed to M Fromm.

At least 73 records · Page 4Linked to original sources

PubMed1998

Epithelial tight junction structure in the jejunum of children with acute and treated celiac sprue.

Tight junction morphology was analyzed in freeze fracture electron micrographs from biopsies at two locations along the surface-crypt axis in the jejunum of children with treated and untreated sprue and in control subjects. In control jejunum, strand number, meshwork depth, and total depth of the tight junction decreased from surface to crypt, consistent with the concept of the crypt being more permeable than the surface epithelium. In acute sprue, strand number was reduced in all regions along the surface-crypt axis, from 5.5+/-0.2 to 3.4+/-0.3 (surface) and from 4.7+/-0.2 to 3.6+/-0.1 (crypt). Meshwork depth was also reduced at all regions along the surface-crypt axis. Strand discontinuities were more frequent in acute sprue. Aberrant strands appeared below the main meshwork of crypt tight junctions in acute sprue. In asymptomatic children treated with the gluten-free diet, jejunal tight junctional structure only partially recovered. Strand number was restored to normal at the surface, but was still decreased in the crypts, from 4.7+/-0.2 to 3.9+/-0.3. We conclude that the epithelial barrier function of the small intestine is seriously disturbed by structural modifications of the tight junction in acute symptomatic celiac disease, thereby accounting for increased ionic permeability noted in a parallel study on identical specimens. This epithelial barrier defect may contribute to diarrhea in celiac disease by a "leak flux mechanism." In children with sprue treated with a gluten-free diet, barrier dysfunction was only partly recovered, suggesting a level of "minimal damage."

Celiac Disease↗

PubMed1998

[Lack of effect of EGF on epithelial barrier function in experimental TNBS colitis].

This study tested the hypothesis that EGF has a protective effect on the intestinal barrier function in experimental TNBS-induced colitis. EGF was given intraperitoneally one hour before and 24 hours after induction of colitis. The rats were killed 48 hours after induction of colitis: The distal colon was resected and mounted into Ussing chambers. Flux measurements were performed for Na+ and mannitol, and epithelial and subepithelial resistances were determined. A semiquantitative histological score was used to grade acute and chronic inflammation. Compared to controls, TNBS caused a 3-fold increase in both fluxy, indicating enhanced paracellular permeability. There rates was a severe reduction of total and epithelial resistances indicating a dramatic defect of epithelial barrier function. EGF failed to improve the electrophysiologic and histologic parameters. Therefore, EFG has no protective effective in experimental TNBS colitis.

Animals↗

PubMed1998

[Zinc acts as a protective agent on the mucosal barrier in experimental TNBS colitis].

The aim of this study was to analyze the effect of enterally given zinc on the impaired epithelial barrier function in experimental TNBS colitis in rats. Rats in therapy group were zinc-fed in therapeutic dose. 48 hours after induction of TNBS colitis the rats were killed, the distal colon was resected and mounted into an Ussing chamber. The following electrophysiological measurements were carried out: 1. Flux measurements for Na+ and mannitol as a parameter of paracellular permeability, 2. Resistance measurements of the colon, distinguishing between pure epithelial resistance and resistance of the subepithelial tissue. In TNBS colitis we found a marked increase of both fluxes as a parameter of enhanced paracellular permeability (factor 3). Further there was a drastic reduction of total resistance, and especially of pure epithelial resistance indicating a massive epithelial barrier defect. In rats treated by zinc the increase of paracellular permeability was increased only by a factor of 2, and there was only a moderate decrease of resistance. For the first time we demonstrated zinc to have a protective effect on damaged mucosal barrier function in TNBS colitis. These results confirm the data collected in guinea pigs with malnutrition, whose intestinal integrity could be improved by zinc. Further studies are necessary in order to test whether this protective effect of zinc on mucosa barrier in experimental colitis may be relevant also in human ulcerative colitis.

Administration, Oral↗

PubMed1998

[Changes in permeability after ileoanal pouch anastomosis and in pouchitis].

The aim of the present study was to determine the changes in permeability and mucosal function after ileo-pouchanal anastomosis (IPAA) in patients with ulcerative colitis. We examined 24 patients (m: f = 15:9; Age = 35.2 +/- 12.5) prior to colectomy (pre IPAA), prior to closure of ileostomy (pre CIS), after closure of ileostomy (post CIS), in case of pouchitis and 5 controls. With a miniaturizised Ussing-chamber electrophysiological parameters of permeability and resorptive isotope-fluxes for mannitol were measured. Total resistance could be differenciated into epithelial and subepithelial resistance by using alternating current impedance measurements. Active Na(+)-glucose-Cotransport was measured by detection of the maximal short-curcuit-current under stepwise addition of glucose and active Cl(-)-secretion was measured by the increase in short-curcuit-current after stimulation with Theophillin and PGE2. Epithelial resistance of pouchitis was slightly raised towards controls but did not differ from the others. Subepithelial resistance post CIS and pouchitis was significantly increased versus controls and pre CIS (21.2 +/- 22.4 vs. 10.7 +/- 13.3 omega cm2) Whereas Cl-secretion of pouchitis was significantly reduced vs. post CIS and controls (38.6 vs. 120.9 +/- 113.9 microA cm-2). In the same way Na(+)-glucose Cotransport of pouchitis was significantly reduced vs. post CIS and controls(41.8 vs. 138.4 +/- 264.4 microA cm-2). Increasing subepithelial resistance post CIS and in pouchitis is a hint for an adaptive thickening of the subepitheal layer. Concerning the functional analysis pouchitis and terminal ileum prior to IPAA show a reduced secretion and resorption whereas the mucosal barrier towards Mannitol remains unchanged.

Biopsy↗

PubMed1998

Dual versus triple therapy: comparison of five antibiotic regimens for eradication of Helicobacter pylori in a prospective, randomized study.

We compared the efficacy of three dual and two triple therapies for eradication of Helicobacter pylori (HP), and evaluated the influence of smoking and omeprazole pretreatment on HP eradication. 220 patients with proven HP infection (histology and 13C-urea breath test [UBT]) were randomly allocated to one of the following regimes: BMT (bismuth subsalicylate 600 mg t. i. d. for 28 days, metronidazole 400 mg t. i. d. and tetracycline 500 mg q. i. d. for ten days). OA (omeprazole 40 mg o. d. and amoxicillin 750 mq q. i. d. for 14 days), OC (omeprazole 40 mg o. d. and clarithromycin 500 mg b. i. d. for 14 days), OT (omeprazole 40 mg o. d. and tetracycline 500 mg q. i. d. for 14 days), OMC (omeprazole 40 mg o. d., metroinidazole 400 mg t. i. d. and clarithromycin 250 mg b. i. d. for seven days). Eradication was defined as negative UBT six weeks after completion of the therapy. In an "all-patients-treated" ("per-protocol") analysis, the eradication rates were: BMT, 91% (93%); OA, 84% (90%); OC, 74% (74%); OT, 24% (24%); and OMC, 90% (93%). Smoking impaired the success of OA and OT (p < 0.05), but the efficacy of the triple regimens was not affected. Omeprazole pretreatment did not influence eradication rates. Thus, highest eradication rates were achieved with the two triple therapies tested. However, OA, given at a daily antibiotic dose of 3 g amoxicillin for 14 d, was also highly effective. After failure of triple therapy, OA was successful in seven of ten patients (70%). The efficacy of OC was lower than that of the triple therapies (p < 0.05). In conclusion, metronidazole- and clarithromycin-based triple therapies are highly effective first line therapies. OA, given at a dose of 3 g per day over 14 days, should be considered as a possible second line therapy, e.g. in retherapy after failed triple therapy.

Adolescent↗

PubMed1997

Ussing chamber for high-frequency transmural impedance analysis of epithelial tissues.

An Ussing chamber was designed for impedance analysis of epithelial tissue and optimized for the use of high-frequency alternating current stimuli. Shielded voltage electrodes, located axially within the electric field of the Ussing chamber, minimized the reactive properties of the set-up. By vectorial subtraction, the small reactive contribution of the optimized Ussing chamber was completely compensated for. This method allowed for transmural impedance measurements in a frequency range of 1-65 kHz. For the first time, Nyquist plots of cultured intestinal cell monolayers (HT-29/B6) are presented. The epithelial monolayers in different stages of confluence showed the impedance locus as a semicircle, with the high frequency end close to the origin. These epithelial monolayers could be modeled by a simple RC-parallel circuit without a series resistance.

Electric Impedance↗

PubMed1997

Pure embryonal rhabdomyosarcoma of the fallopian tube.

Rhabdomyosarcoma is a neoplasm of childhood which commonly arises in the genitourinary tract. Reported locations include the bladder, prostate, paratestis, vagina, uterus, cervix, and ovary. Rhabdomyosarcomas have been reported to occur in the fallopian tube only as a component of a malignant mixed müllerian tumor. We present a case of pure embryonal rhabdomyosarcoma of the fallopian tube in a 17-year-old. The diagnosis was confirmed by immunohistochemical stains. The strongest evidence for the primary location of this pure embryonal rhabdomyosarcoma was the gross appearance of the tumor at laparotomy. Additionally, rhabdomyosarcomas arising from adjacent organs have never been reported to grow into the fallopian tubes.

Adolescent↗

PubMed1997

Differential stimulation of intestinal mucin secretion by cholera toxin and carbachol.

Cholinergic stimulation triggers the secretion of apically stored, preformed mucin from goblet cells but the pathway of cAMP-stimulated mucin secretion is not known. In this study the effect of cholera toxin on mucin secretion in the human colonic goblet cell line HT-29/B6 was investigated and compared to the action of carbachol. PAS staining of mucin blotted onto nitrocellulose served to quantify the secretion of total mucin. Metabolic labelling was used to evaluate the secretion of newly synthesized mucin. The mucinous nature of the detected material was confirmed with an immunoblot employing a well-characterized polyclonal antibody reacting with MUC2-mucin. Cholera toxin caused a 116-fold increase of intracellular cAMP and strongly stimulated the secretion of both preformed and newly synthesized mucin for more than 20 h. Carbachol only triggered the release of preformed mucin immediately after addition. The secretory response to cholera toxin could be partly inhibited by the protein kinase A inhibitor H8 and the microtubule inhibitor colchicine. The action of carbachol was not affected by these agents. In conclusion, we demonstrate a direct cAMP-dependent effect of cholera toxin on mucin secretion by intestinal goblet cells. In contrast to carbachol, the action of cholera toxin involves de novo synthesis of mucin molecules and microtubule-mediated secretion. There seem to be distinct secretion pathways for muscarinic or cAMP-dependent stimulation of mucin secretion.

Calcium↗

PubMed1997

Measurement of paracellular epithelial conductivity by conductance scanning.

A new method, conductance scanning, allows determination of local para- and transcellular conductivities in flat epithelia. Experiments were performed on kidney distal tubule cells, MDCK clone C11, which form monolayers on permeable supports. Above the apical surface, local voltage drops generated by a sinusoidal current clamp were recorded by means of a scanning microelectrode. Data were collected above cell centres and tight junctions. The scanning signal was always significantly higher above the tight junctions, but was uniformly distributed along the junctions. For determination of conductivities two procedures were applied. Method 1: the supraepithelial potential distribution was computed for given trans- and paracellular currents at all positions of the electrode. In a fit algorithm, the currents were varied until the calculated potential difference equalled the voltage measured. Method 2: after collecting scanning data in control Ringer's, intercellular space width was reduced by mucosal addition of 40 mM sucrose and a second set of data was obtained at decreased paracellular, but presumably unchanged transcellular, conductivity. From these data, trans- and paracellular conductivities were calculated. Results of both methods were in excellent agreement. Confluent MDCK-C11 monolayers exhibited a transepithelial conductivity of 13 mS/cm2. The transcellular pathway contributed 2.6 mS/cm2 (20%) and the paracellular pathway 10. 5 mS/cm2 (80%) to the total conductivity. Collapse of the lateral intercellular spaces decreased the paracellular conductivity to 4 mS/cm2 (60%). Confluent MDCK-C11 monolayers constitute true "leaky" epithelia with homogeneously distributed trans- and paracellular conductivities. In conclusion, conductance scanning fills a methodical gap, which hitherto impeded the functional characterization of tight junctions.

Animals↗

PubMed1997

13C-urea breath test in Helicobacter pylori diagnosis and eradication. Correlation to histology, origin of 'false' results, and influence of food intake.

BACKGROUND: Which protocol is optimal for the 13C-urea breath test (UBT) for Helicobacter pylori detection is controversial. This study aimed to characterize a very simple UBT protocol for the clinical routine (two-point-analysis performed with 75 mg 13C-urea and citric acid) with special consideration of 'false' UBT results. RESULTS; UBT was evaluated in reference to histology (Warthin-Starry). In mismatching results re-gastroscopy was performed. By UBT, 74 of 77 patients with H. pylori-positive histology were detected (sensitivity, 96%). The false-negative UBTs were due to low colonization densities during spontaneous H. pylori elimination or pyloric obstruction. Seven of 49 patients with negative histology had a positive UBT, but re-gastroscopy showed that all of them had a positive histology when multiple antral biopsy specimens were taken (UBT specificity, 100%). UBT correlated only weakly with H. pylori colonization density. No correlation was found between UBT and gastric neutrophil and lymphocyte infiltration. UBT reproducibility was excellent (93 of 94 in a 6-month period). Non-fasting conditions induced a shift to lower UBT results in H. pylori-positive and to higher UBT results in negative patients, resulting in 2 of 10 false-positive and 1 of 10 false-negative UBTs. CONCLUSION: This simple version of the urea breath test combines the highest sensitivity with excellent reproducibility. It is superior to histologic detection of H. pylori in the clinical routine and an optimal tool for monitoring H. pylori eradication. Fasting conditions are required for the test.

Breath Tests↗

PubMed1996

Segmental heterogeneity of swelling-induced Cl- transport in rat small intestine.

The effect of cell swelling induced by hypotonic media was studied in segments of rat small intestine. In the Ussing chamber, exposure to a hypotonic medium caused a decrease in short-circuit current (Isc) and potential difference (Vms) in the jejunum, whereas the ileum responded with an increase in Isc and Vms. The transition from one pattern to the other was located about in the middle of the small intestine. Tissue conductance decreased in both segments, probably due to a reduction of paracellular shunt conductance induced by the cell swelling. Voltage scanning experiments revealed that the observed decrease in total tissue conductance in the ileum was caused solely by a decrease in local conductance in the villus region while the crypt conductance did not change, suggesting that the decrease in paracellular conductance of the crypts is compensated by an increase in cellular conductance. The response in both segments was dependent on the presence of Cl- and was blocked by the Cl- channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB). It was not affected by the neurotoxin tetrodotoxin. In the jejunum the swelling-induced decrease in Isc was reduced in the presence of the cyclooxygenase inhibitor, indomethacin, or the lipoxygenase inhibitor, nordihydroguaiaretic acid. In the ileum the Cl- secretion induced by hypotonicity was blocked by the K+ channel blocker quinine and was reversed into a decrease in Isc when serosal Ca2+ was zero. We conclude that the observed volume regulatory changes are initiated in the jejunum by an eicosanoid-mediated opening of basolateral Cl- channels and in the ileum by a Ca2+-mediated opening of K+ channels which enhances apical Cl- efflux.

Animals↗

PubMed1996

Tumor necrosis factor-alpha induces Cl- and K+ secretion in human distal colon driven by prostaglandin E2.

Increased levels of tumor necrosis factor-alpha (TNF-alpha) have been found in, for example, inflammatory bowel disease (IBD) and human immunodeficiency virus (HIV) infection. To investigate a possible contribution of TNF-alpha to the pathogenesis of diarrhea in these diseases, ion transport of human distal colon was studied in the Ussing chamber in vitro. Serosal addition of TNF-alpha increased short-circuit current (Isc) of partially stripped tissues in a dose-dependent manner. Maximum Isc increase of 1.8 +/- 0.2 mumol.h-1.cm-2 was reached after 60 +/- 9 min at 200 ng/ml TNF-alpha. Bidirectional tracer flux measurements revealed that TNF-alpha induced an increase in 36 Cl serosal-to-mucosal flux, a decrease in 36Cl- mucosal-to-serosal flux, and a slight increase in K+ secretion indicated by an increased secretory 86Rb net flux. In the highly differentiated colonic epithelial cell line HT-29/B6, TNF-alpha had no effect on Isc, suggesting a mediation step located in the subepithelium. This supposition was supported by measurements on totally stripped human tissues, since removal of subepithelial layers by total stripping reduced the TNF-alpha effect by 40%. Experiments with tetrodotoxin (10(-6)M) indicated that the TNF-alpha effect was not mediated by the enteric nervous system. The specific 5-lipoxygenase blocker ICI-230487 (5 x 10(-8)M) also had no effect on TNF-alpha action. In contrast, inhibition of cyclooxygenase by indomethacin (10(-6)M inhibited the effect of TNF-alpha. Radioimmunoassay of prostaglandin E2 (PGE2) in the serosal bathing solution revealed an increase in PGE2 production/release after addition of TNF-alpha, which paralleled the Isc response. We conclude that TNF-alpha changed Cl- and K+ transport toward secretion in human colon. This effect was mediated by PGE2 produced by subepithelial cells. Thus TNF-alpha could be a mediator of diarrhea during intestinal inflammation, e.g., in IBD and HIV infection.

Biological Transport↗

PubMed1995

Morphometric parameters of living human in-vitro fertilization embryos; importance of the asynchronous division process.

A total of 304 human pronuclear zygotes and cleaved embryos from the 2- to 9-cell stages, obtained during invitro fertilization attempts, were photographed and retrospectively analysed after transfer for their morphology and size in relation to their developmental stage, using the Imagenia programme of a Biocom 500 image analyser. Morphometric parameters were calculated from the perimeters, surface measurements, theoretical diameters and circularity factors for the different structures analysed. This report provides the morphometric characteristics of living embryos. For the whole population the mean values were: 157.4 microns for the external zona pellucida diameter, 121.8 microns for the internal zona pellucida diameter, 17.9 microns for the thickness of the zona pellucida and 117.2 microns for the embryo cell mass diameter. The morphometric characteristics of the pronuclear-stage population were significantly different from the cleaved cell stages. If the zona pellucida and cell mass embryo diameters increased slowly from the 2- to 9-cell stages, embryonic external diameters were higher and zona pellucida thicknesses were lower in odd than even number blastomere embryos. Preliminary results show that in cases where implantation occurs, the embryo has a lower zona pellucida thickness. A comparison of the different embryo cell stages confirmed the existence of an asynchronous division process during early embryo development. Global results show no evidence of morphometric differences between subpopulations of the embryos according to their microscopic grading. Deviations from the normal asynchronous division process, however, appear to be a new parameter to take into account during embryo scoring.(ABSTRACT TRUNCATED AT 250 WORDS)

Blastocyst↗

PubMed1995

Epithelial barrier and ion transport in coeliac sprue: electrical measurements on intestinal aspiration biopsy specimens.

Epithelial barrier function and ion transport was studied in coeliac sprue using a miniaturised Ussing device for measurements on diagnostic aspiration biopsy specimens from the jejunum of untreated or gluten free nourished sprue patients, or from healthy controls. Pure epithelial resistance (Re) indicating epithelial barrier function was determined by transmural alternating current impedance analysis. It was reduced by 56% in acute sprue mean (SEM) (9 (1) omega.cm2) compared with controls (20(2) omega.cm2). In gluten free nourished sprue patients Re was only partly recovered (15 (1) omega.cm2). Subepithelial resistance (Rsub) was also changed from 28 (1) omega.cm2- in control to 17 (1) omega.cm2 in acute sprue because of the change in mucosal architecture, but was unchanged in gluten free nourished sprue patients (29 (4) omega.cm2). In acute sprue, unidirectional Na+ and Cl- fluxes were increased in both directions as a consequence of the decreased resistance. However, short circuit current (ISC) as well as Na+ and Cl- net fluxes were not significantly different from control. Subsequently, the electrogenic Cl- secretory system was investigated. After maximal stimulation with theophylline and prostaglandin E1, a Cl(-)-dependent increase in ISC was obtained in the sprue mucosa and control jejunum. It showed saturation characteristics and was blockable by serosal bumetanide. When compared with control, neither Km nor Vmax of this electrogenic Cl- secretion was significantly changed in coeliac sprue. In conclusion, a miniaturised Ussing device was used for transport measurements on intestinal biopsy specimens. In acute coeliac disease, the epithelial barrier of the jejunum was seriously disturbed. The active electrogenic Cl- secretory transport system was present in the sprue mucosa, but was not activated in the Ussing chamber in vitro when compared with control jejunum.

Acute Disease↗

PubMed1995

Distension-induced electrogenic Cl- secretion is mediated via VIP-ergic neurons in rat rectal colon.

Distension of rat rectal colon causes electrogenic Cl- secretion via the plexus submucosus Meissner. This study aimed to identify the neurotransmitter(s) of this reflex pathway. Distension was applied to partially stripped rat rectal colon in Ussing chambers. Baseline short-circuit current (Isc) increased and then slowly declined again within 30 min. The increase in Isc 10 min after distension (delta Isc10) was 1.8 +/- 0.3 mumol.h-1.cm-2. Atropine (1 microM) did not alter delta Isc10. Thus cholinergic neurons with muscarinic synapses were not involved. Tissues were then desensitized to vasoactive intestinal peptide (VIP) or substance P. This required continuous infusion of VIP or substance P into the chamber; otherwise, desensitization was only temporary due to rapid degradation of VIP or substance P. During substance P desensitization, distension still induced a secretory response (delta Isc10 not significant vs. control), whereas during VIP desensitization distension no longer had an effect. Furthermore, a polyclonal anti-VIP antiserum blocked 81% and the VIP antagonist [p-Cl-D-Phe6,Leu17]VIP blocked 89% of the distension-induced delta Isc10, supporting the results of the desensitization experiments. To localize the site of VIP action, tetrodotoxin (TTX) was used. The TTX effect on Isc during VIP stimulation was not different from its effect on baseline Isc. This is in accord with the concept that the VIP receptors are mainly located on the enterocytes. We conclude that VIP, but not substance P or acetylcholine (via muscarinic receptors), acts as a neurotransmitter in the distension-induced reflex pathway, causing Cl- secretion in rat rectal colon.

Animals↗

PubMed1995

Enzyme- and mineralocorticoid receptor-controlled electrogenic Na+ absorption in human rectum in vitro.

In vivo electrogenic Na+ absorption (JeNa) in the human rectum is controlled by acute variation of aldosterone in nanomolar concentration range. In this study we report both the induction of JeNa in human rectum epithelium by nanomolar aldosterone added in vitro and the enzymatic control of glucocorticoid action on JeNa. JeNa was measured as amiloride-sensitive short-circuit current 8 h after addition of the respective steroid. Aldosterone (10 nM) caused JeNa of 5.7 +/- 1.4 mumol.h-1.cm-2. Cortisol in the same concentration did not induce significant JeNa. Because cortisol is readily inactivated by 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), the true mineralocorticoid activity of cortisol was evaluated after inhibition of 11 beta-HSD by carbenoxolone. Carbenoxolone alone did not exhibit mineralocorticoid activity. If cortisol (10 nM) was given together with carbenoxolone (1 microM), the resulting JeNa (4.5 +/- 0.4 mumol.h-1.cm-2) was not significantly different from that after 10 nM aldosterone, indicating equal intrinsic mineralocorticoid activity of cortisol and aldosterone. The same mechanisms were found in rat late distal colon. Kinetic data of carbenoxolone at 10 nM cortisol resulted in a Michaelis constant of 0.3 microMs, maximal absorption of 8.4 mumol.h-1.cm-2, and a Hill coefficient of 1.8. The effects of carbenoxolone and glycyrrhetinic acid did not differ. We conclude that JeNa is under complete control of mineralocorticoid action. "Spontaneous" JeNa in the beginning of the in vitro period can be explained by elevated steroid levels before tissue removal.(ABSTRACT TRUNCATED AT 250 WORDS)

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1994

Gestational age dependence of 11 beta-hydroxysteroid dehydrogenase and its relationship to the enzymes of phosphatidylcholine synthesis in lung and liver of fetal rat.

Increase in fetal surfactant synthesis and lung maturity is caused by the glucocorticoidal induction of enzymes required for phosphatidylcholine (PC) synthesis towards the end of gestation. The regulation of gestational age-dependent induction of PC synthesis by glucocorticoids is still unclear. Since 11-beta-hydroxysteroid dehydrogenase (11 beta-HSD) activity and its metabolising capacity for glucocorticoids have been suggested to play a central role in this regulation, we measured the gestational age-dependent changes in 11 beta-HSD and PC synthesizing enzymes in lung and liver of fetal rat. The activity of cholinephosphate cytidyltransferase (CCT; key enzyme in PC synthesis), choline phosphotransferase (CPT) and lysolecithin acyltransferase (LAT) were found to increase gradually in the lung towards the end of gestation, reached peak values at term followed by a decrease of activity reaching finally adult levels. Only CK activity exhibited constant levels until term followed by a slight increase after the birth. In comparison with the lung, the liver enzymes followed a similar pattern, but at a higher rate of activity except for CCT which was higher in the lung. The activity of 11 beta-HSD in fetal lung microsomes was detectable from day 20 and increased towards the end of gestation in the lung and liver of the rat. Oxidase activity was always found to exceed the reductase activity. The activity of 11 beta-HSD continued to increase after delivery and reached peak levels in adult animals in both organs. In order to test the hypothesis, whether 11 beta-HSD activity and PC synthesis are induced by increasing endogenous glucocorticoidal levels, we examined on day 19 of gestation the effect of dexamethasone (DEXA) on enzymatic activities (11 beta-HSD, CCT) and on [14C]choline incorporation in phosphatidylcholine in fetal lung organoid cultures. Additionally, changes in CCT activity in fetal lungs after maternal administration of DEXA were measured. DEXA accelerated 11 beta-HSD and CCT activities as well as [14C]choline incorporation. We conclude, that endogenous glucocorticoids induce PC synthesis as well as 11 beta-HSD activity in lung and liver of the fetal rat. Fetal PC synthesis is not altered by increasing 11 beta-HSD levels, because the increase of free serum corticosterone levels apparently exceeds the metabolising capacity of 11 beta-HSD towards term.

1-Acylglycerophosphocholine O-Acyltransferase↗

PubMed1994

Tight junctions and paracellular permeability in cultured bovine corneal endothelial cells.

Intramembrane specializations of cultured bovine corneal endothelial cells were studied with thin section and freeze-fracture electron microscopy and related to the paracellular permeability and the transendothelial resistance (Rt) of the monolayers. The following intercellular junctions were found: single and discontinuous networks of tight junctions (TJ) which girdle the apico-lateral cell perimeter incompletely, gap junctions, and membrane undulations suggesting intermediate junctions. The macromolecular tracer ruthenium red penetrated into the lateral intercellular space beyond the level of the incomplete belt of TJ. Rt of these monolayers was 20.9 +/- 1.0 omega.cm2. Protamine induced a reversible increase of Rt to 118 +/- 5% of its control value. We conclude that incomplete belts of TJ may be the morphological counterpart of the high paracellular permeability of this monolayer and functionally and morphologically resemble those of their native endothelium. Cultured corneal endothelial cells are an excellent model for studying the influence of incomplete belts of TJ on paracellular permeability of cells.

Animals↗