Strongyloides ratti: Dissociation of the rat's protective immunity into systemic and intestinal components

Analysis of the early stages of a challenge infection with Strongyloides ratti has shown that protection is expressed against the developing third-stage larval worms (L₃) and prevents the maturation to adulthood of most larvae. Challenge after an immunizing infection that was restricted to the parenteral L₃ migratory phase showed that some 10–40% of overall protection could be ascribed to systemic antilarval immunity. Some larvae were trapped in the skin at the site of injection whereas others failed to migrate to the head and lung of immune rats. Larvae arriving in the intestine at Days 3, 4, and 5 did not persist beyond Day 7 and 8. Studies using [⁷⁵Se]methionine-labeled L₃ showed a significant increase in fecal label in rats immunized by a complete infection. This loss did not occur to the same extent in rats immunized only with parenteral larvae. Significant rejection of worms transplanted to the intestine also indicated intestinal protection. The possible existence of large numbers of worms in a state of “arrested development” was excluded by their failure to appear after cortisone treatment and the absence of worm accumulation in radiolabeling studies. It is concluded that at least two responses operate against larval S. ratti, one is systemic and the other operates in the intestine against larvae in a manner that resembles the “rapid expulsion” rejection of Trichinella spiralis in immune rats.     

Trichinella spiralis: Immunization of rats with an antigen fraction enriched for allergenicity

Trichinella spiralis whole muscle larval extract was fractionated by gel filtration and anion-exchange chromatography, and the protein fractions were assayed for allergenicity by a footpad-swelling test in mice; IgE antibody levels in rats immunized with the fractions were determined by passive cutaneous anaphylaxis test in rats. By these methods, an allergenic fraction from T. spiralis was isolated. The fraction, F1-b, was shown to be monodisperse by analysis with SDS-PAGE, IEP, and isoelectric focusing, indicating that it is a single protein moiety with a molecular weight of approximately 45,000 and a pI of approximately 5.1. The Schiff-periodate test showed Fl-b to be a glycoprotein. Rats immunized with Fl-b had significantly fewer intestinal worms than did nonimmunized controls at 24 hr and 7 days after oral challenge with T. spiralis larvae.     

Na,K-ATPase and the development of Na+ transport in rat distal colon

Summary Na, K-ATPase function was studied in order to evaluate the mechanism of increased colonic Na⁺ transport during early postnatal development. The maximum Na⁺-pumping activity that was represented by the equivalent short-circuit current after addition of nystatin (I _sc ^N ) did not change during postnatal life or after adrenalectomy performed in 16-day-old rats.I _sc ^N was entirely inhibited by ouabain; the inhibitory constant was 0.1mm in 10-day-old (young) and 0.4mm in 90-day-old (adult) rats. The affinity of the Na, K pump for Na⁺ was higher in young (11mm) than in adult animals (19mm). The Na, K-ATPase activity (measured after unmasking of latent activity by treatment with sodium dodecylsulfate) increased during development and was also not influenced by adrenalectomy of 16-day-old rats. The inhibitory constant for ouabain (K _I ) was not changed during development (0.1–0.3mm). Specific [³H]ouabain binding to isolated colonocytes increased during development (19 and 82 pmol/mg protein), the dissociation constant (K _D ) was 8 and 21 m in young and adult rats, respectively. The Na⁺ turnover rate per single Na, K pump, which was calculated fromI _sc ^N and estimated density of binding sites per cm² of tissue was 500 in adult and 6400 Na⁺/min·site in young rats. These data indicate that the very high Na⁺ transport during early postnatal life reflects an elevated turnover rate and increased affinity for Na⁺ of a single isoform of the Na, K pump. The development of Na⁺ extrusion across the basolateral membrane is not directly regulated by corticosteroids.     

Immunological aspects of murine infection with the rat nematode Strongyloides ratti Sandground, 1925

In a study of the immune response of the rat to infection with the nematode Strongyloidis ratti, the antigens of the infective larval stage (L3) and of the parasitic, parthenogenetic female (Fp) were investigated. From both the larvae and the adult females, one metabolic (exoantigen) and two somatic antigens were extracted. Of the two somatic antigens, one was soluble and obtainable by physical means while the other was separated by chemical means from the tegument of the parasite. Humoral responses to the various antigens were evaluated by immunodiffusion and ELISA techniques, while the overall immune response was assayed by the worm burden in the immunized and subsequently infected rats. Agar-gel double diffusion yielded precipitin bands only with larval somatic antigens. ELISA proved positive at a titer of 20,000 with larval metabolic antigen and sera of rats immunized against either larval metabolic or somatic antigens. By 20 days post challenge infection, however, this titer diminished to 4000. In vivo studies of worm burden in rats immunized with the various antigens and then exposed to the live L3 of the nematode showed that there were significantly fewer adult worms in the rats immunized with larval somatic antigen and adult metabolic antigen than in those immunized with adult somatic antigen or larval metabolic antigen.     

The fate of multiple doses of infective larvae of Nematodirus battus in 8-month-old lambs and their effect on intestinal enzyme activity

Mapes C.J. and Coop R.L. 1973. The fate of multiple doses of infective larvae of Nematodirus battus in 8-month-old lambs and their effect on intestinal enzyme activity. International Journal for Parasitology3: 363–370. The fate of five daily doses of 60,000 infective larvae of Nematodirus battus was studied in 8-month-old lambs. On 18, 26 and 34 days after the last larval dose 4.0, 3.3 and 1.0 per cent of the total infective dose was recovered. Approximately 50 per cent of the worms recovered on these days were fourth-stage larvae. It is suggested that L5 and adult stages were preferentially lost from the hosts and that male worms were developing at a faster rate than the females. The populations of N. battus were smaller, contained higher proportions of fourth-stage larvae and shorter L5 and adult worms than those developing from similar infective doses in 3-month-old lambs. A transient decrease in alkaline phosphatase and maltase levels was found in the mucosa of the small intestine and was compared with the marked and persistent changes in mucosal enzyme activities found with similar infective doses in 3-month-old hosts.     

Effects of aldosterone on Na transport in the toad bladder II. The anaerobic response

The action of aldosterone on active Na⁺ transport was assessed under aerobic and anaerobic conditions in the isolated urinary bladder of the toad, BUfo marinus. Aldesterone augmented the short-circuit current (I_sc) under rigorous anaerobiosis. Four lines of evidence indicate that the increase in anaerobic I_sc does not represent an equivalent increase in active Na⁺ transport: 1. Net Na⁺ transport, determined by isotopic fluxes, was the same in the aldosterone-treated and control quarter-bladders, and significantly greater than the simultaneously measured I_sc. 2. Amiloride, an inhibitor of the apiral entry of Na⁺, did not reduce the steroid-dependent increase in the anaerobic I_sc. 3. Substitution of choline for Na⁺ in the mucosal medium reduced the magnitude of the anaerobic I_sc values did not eliminate the effect of aldosterone. 4. Addition of ouabain, a potent inhibitor of the Na⁺ pump, partially inhibited the effect of aldosterone on the anerobic I_sc but a significant hormonal increment remained. The source of the anaerobic I_sc was not identified; an effort was made, however, to determine the dependence of this current on glycolysis. During anaerobics, aldosterone increased the integral I_sc by 42% but did not alter lactate production. These results suggest that the steroid-dependent increase in the anaerobic I_sc may involve effects on permeability properties of the epithelium rather than on active tranport systems.     

Na+ channel activity in cultured renal (A6) epithelium: Regulation by solution osmolarity

Summary Solution osmolarity is known to affect Na⁺ transport rates across tight epithelia but this variable has been relatively ignored in studies of cultured renal epithelia. Using electrophysiological methods to study A6 epithelial monolayers, we observed a marked effect of solution tonicity on amiloride-sensitive Na⁺ currents (I _sc).I _sc for tissues bathed in symmetrical hyposmotic (170 mOsm), isosmotic (200 mOsm), and hyperosmotic (230 or 290 mOsm) NaCl Ringer's solutions averaged 25±2, 9±2, 3±0.4, and 0.6±0.5 A/cm², respectively. Similar results were obtained following changes in the serosal tonicity; mucosal changes did not significantly affectI _sc. The changes inI _sc were slow and reached steady-state within 30 min. Current fluctuation analysis measurements indicated that single-channel currents and Na⁺ channel blocker kinetics were similar for isosmotic and hyposmotic conditions. However, the number of conducting Na⁺ channels was approximately threefold higher for tissues bathed in hyposmotic solutions. No channel activity was detected during hyperosmotic conditions. The results suggest that Na⁺ channels in A6 epithelia are highly sensitive to relatively small changes in serosal solution tonicity. Consequently, osmotic effects may partly account for the large variability in Na⁺ transport rates for A6 epithelia reported in the literature.     

Na and Cl transport and short-circuit current in rabbit ileum

Summary Na and Cl fluxes and short-circuit current (I _sc) in rabbit ileum have been studied as a function of ionic concentrations in HCO₃-free solutions. Both net Na flux (J _net ^Na ) andI _sc show similar saturation functions of [Na] at fixed [Cl]. They show no significant difference between zero and 112mm Na but at 140mm NaI _sc is significantly greater than theJ _net ^Na . Net Cl transport, secretion, is observed only at 140mm Na and is approximately equivalent to the difference between theI _sc andJ _net ^Na . The transcellular mucosa-to-serosa Na fluxes measured at 140 and 70mm Na do not differ significantly from the correspondingI _sc. The net Cl flux varies with [Cl] at fixed [Na] whileI _sc is virtually not affected by [Cl]. These results suggest that the absorptive Na transport process is electrogenic and responsible for theI _sc and that the secretory fluxes of Na and Cl are coupled, require high [Na], vary with [Cl], and do not contribute toI _sc. K-free solution abolishes theI _sc after a prolonged lag. Finally, the effect of a low resistance shunt pathway on active Na absorption is examined with a four-compartment model.Deceased (October 16, 1974).     

Ion transport across the skin of a larval salamander

The transport characteristics of the skin of neotenic Ambystoma tigrinum were investigated using ion substitution and circuit analysis. When bathed with sodium Ringer solution on both sides, a transepithelial potential of up to 50 mV (inside positive) and a short-circuit current (I_sc) of up to 10 μA/cm² were observed. When amiloride was added or Na⁺ was replaced by tetramethylammonium in the apical solution, I_sc was decreased from 3.7 ± 0.4 to 1.5 ± 0.2 μA/cm² (n = 10). When K⁺ replaced Na⁺, there was a smaller change in I_sc from 5.8 ± 0.6 to 3.7 ± 0.5 μA/cm² (n = 10). Although barium had no effect when added to 100 K Ringer on normal skin, it inhibited I_sc on skins taken from K⁺-loaded animals. Nystatin caused substantial increases in I_sc with either Na⁺ or K⁺ as the dominant cation in the apical solution. Current voltage analysis using amiloride was used to estimate the resistances and electromotive forces (EMF) associated with ion transport. The EMF for ion transport was partially dependent on K⁺ in the basolateral solution and it was similar to that observed in other epithelia. The resistance of the transport pathway was high, consistent with the low I_sc. These results suggest that there is an amiloride-sensitive Na⁺ channel in parallel with a small K⁺ conductance in the apical membrane of this preparation.     

Effects of epinephrine, glucagon and vasoactive intestinal polypeptide on chloride secretion by teleost opercular membrane

Summary The effects of epinephrine, glucagon and vasoactive intestinal polypeptide on chloride secretion by chloride cell-containing isolated opercular membranes from the seawater-adapted euryhaline teleost, the tilapiaSarotherodon mossambicus, have been examined. Epinephrine inhibits chloride secretion, measured as the short-circuit current (I _sc), via -receptors, in a dose-dependent fashion. The minimum effective dose is 10^–9 M, ED₅₀ equals 2×10^–7 M and maximal inhibition at 10^–5 M is nearly 80%. Inhibition of phosphodiesterase by isobutylmethylxanthine (IBMX; 10^–4 M), does not alterI _sc in untreated tissues, but it completely reverses the epinephrine inhibition ofI _sc, suggesting that hormones which modulate cAMP in chloride cells may alter chloride secretion. Glucagon and vasoactive intestinal polypeptide also stimulateI _sc in epinephrine-inhibited tissues, an effect potentiated by IBMX. The effect of glucagon is dose-dependent with a minimum effective dose of 10^–9 M, ED₅₀ equal to 8×10^–8 M and a maximum stimulation of 72% at 10^–5 M.Analysis of the effects of epinephrine and IBMX onI _sc and tissue conductance suggests that these agents act antagonistically on a nonconductive transport mechanism. It is proposed that IBMX and hormones which increase intracellular cAMP levels stimulate chloride secretion in epinephrine-inhibited tissues by stimulating a neutral sodium chloride cellular entry-step mechanism.Abbreviations ED ₅₀ effective dose causing half-maximal inhibition or stimulation - IBMX isobutylmethylxanthine - VIP vasoactive intestinal polypeptide     

Stimulation of Transepithelial Na<Superscript>+</Superscript> Current by Extracellular Gd<Superscript>3+</Superscript> in <Emphasis Type="Italic">Xenopus laevis</Emphasis> Alveolar Epithelium

In the present study we investigated the effect of extracellular gadolinium on amiloride-sensitive Na⁺ current across Xenopus alveolar epithelium by Ussing chamber experiments and studied its direct effect on epithelial Na⁺ channels with the patch-clamp method. As observed in various epithelia, the short-circuit current (I _sc) and the amiloride-sensitive Na⁺ current (I _ami) across Xenopus alveolar epithelium was downregulated by high apical Na⁺ concentrations. Apical application of gadolinium (Gd³⁺) increased I _sc in a dose-dependent manner (EC ₅₀ = 23.5 µM). The effect of Gd³⁺ was sensitive to amiloride, which indicated the amiloride-sensitive transcellular Na⁺ transport to be upregulated. Benz-imidazolyl-guanidin (BIG) and p-hydroxy-mercuribenzonic-acid (PHMB) probably release apical Na⁺ channels from Na⁺-dependent autoregulating mechanisms. BIG did not stimulate transepithelial Na⁺ currents across Xenopus lung epithelium but, interestingly, it prevented the stimulating effect of Gd³⁺ on transepithelial Na⁺ transport. PHMB increased I _sc and this stimulation was similar to the effect of Gd³⁺. Co-application of PHMB and Gd³⁺ had no additive effects on I _sc. In cell-attached patches on Xenopus oocytes extracellular Gd³⁺ increased the open probability (NP _o) of Xenopus epithelial sodium channels (ENaC) from 0.72 to 1.79 and decreased the single-channel conductance from 5.5 to 4.6 pS. Our data indicate that Xenopus alveolar epithelium exhibits Na⁺-dependent non-hormonal control of transepithelial Na⁺ transport and that the earth metal gadolinium interferes with these mechanisms. The patch-clamp experiments indicate that Gd³⁺ directly modulates the activity of ENaCs.     

Correlation Between Transepithelial Na+ Transport and Transepithelial Water Movement Across Isolated Frog Skin (Rana esculenta)

In the present work the coupling under short-circuited conditions between the net Na⁺-influx across isolated frog skin and the transepithelial transport of water was examined i.e., the short-circuit current (I _sc ) and the transepithelial water movement (TEWM) were measured simultaneously. It has been shown repeatedly that the I _sc across isolated frog skin is equal to the net transepithelial Na⁺ transport. Furthermore the coupling between transepithelial uptake of NaCl under open-circuit conditions and TEWM was also measured. The addition of antidiuretic hormone (AVT) to skins incubated under short-circuited conditions resulted in an increase in the I _sc and TEWM. Under control conditions I _sc was 9.14 ± 2.43 and in the presence of AVT 45.9 ± 7.3 neq cm⁻² min⁻¹ (n= 9) and TEWM changed from 12.45 ± 4.46 to 132.8 ± 15.8 nL cm⁻² min⁻¹. The addition of the Na⁺ channel blocking agent amiloride resulted in a reduction both in I _sc and TEWM, and a linear correlation between I _sc and TEWM was found. The correlation corresponds to that 160 ± 15 (n= 7) molecules of water follow each Na⁺ across the skin. In another series of experiments it was found that there was a linear correlation between I _sc and the increase in apical osmolarity needed to stop the TEWM. The data presented indicate that the observed coupling between the net transepithelial Na⁺ transport and TEWM is caused by local osmosis. Received: 16 October 1996/Revised: 6 March 1997     

Different modes of electrogenic Na+ absorption in the coprodeum of the chicken embryo: role of extracellular Ca2+

Summary Transepithelial electrogenic Na⁺ transport (I_Na) was investigated in the coprodeum of 20-days-old chicken embryos in Ussing chambers. Short circuit current (I_sc) and transepithelial resistance (R_t) were 14.7±4.8 A · cm^-2 (n=12) and 0.53±0.09 k · cm^-2 (n=12), respectively. I_Na was calculated from changes in I_sc by substitution of mucosal Na⁺ by (N-methyl-d-glucamine) (NMDG). I_sc inversed during Na⁺ removal, and I_Na was found to be 27.8±4.7 A · cm^-2 (n=12). Amiloride (100 mol · l^-1) inhibited only about 60% of I_Na. Analysis of I_sc fluctuations revealed a Lorentzian component in the power density spectrum with a corner frequency of about 57 Hz. This component was not correlated to I_Na, and its origin is still unclear. Removal of mucosal Ca²⁺ increased I_Na about 2.5-fold due to an increase of the amiloride-insensitive component of I_Na in additionally investigated adult tissues. The results clearly show that this is due to a non-selective cation channel with an apparent order of selectivity Cs⁺>Na⁺=K⁺>Rb⁺>Li⁺. The Ca²⁺ concentration required to block 50% of the I_sc was about 18 mol · l^-1. The I _sc ^Ca could also be supressed by other divalent cations such as Mg²⁺ and Ba²⁺. Additionally, an I_Na-linked Lorentzian component occurred which dominated the control spectrum with a significantly higher corner frequency (about 88 Hz). The results indicate that Na⁺ absorption in the coprodeum of the chicken embryo is more complex than in adult hens. However, the Ca²⁺ sensitivity of I_Na is similar to comparable effects described for other epithelia. This possibly reflects the existence of two types of amiloride-insensitive apical cation channels as pathways for Na⁺ absorption, which may be involved to differing degrees in ontogenetic developments of nonselective channels to Na⁺-specific ion channels.Abbreviations DPL direct-linear-plot method - slope of the back-ground noise component - EGTA ethylene glycol-bi(2-amino-ethylether)-N,N,N,N-tetraacetic acid - f frequency - f _c corner frequency of the Lorentzian noise component - G _t transepithelial conductance - HEPES N-hydroxyethylpiperazine-N-ethanesulfonic acid - I _sc short-circuit current - I _Na transepithelial sodium current - I _sc ^Ca Ca²⁺-sensitive short-circuit current - K _m ^Ca Michaelis-Menten constant for Ca²⁺ - K _B power density of the background noise component at f=1Hz - m mucosal - NMDG N-methyl-D-glucamine - R _t transepithelial resistance - s serosal - SEM standard error of mean - S(f) power density of the Lorentzian noise component - S _o plateau value of the Lorentzian noise component     

Na+ transport by rabbit urinary bladder,a tight epithelium

Summary By in vitro experiments on rabbit bladder, we reassessed the traditional view that mammalian urinary bladder lacks ion transport mechanisms. Since the ratio of actual-to-nominal membrane area in folded epithelia is variable and hard to estimate, we normalized membrane properties to apical membrane capacitance rather than to nominal area (probably 1 F 1 cm² actual area). A new mounting technique that virtually eliminates edge damage yielded resistances up to 78,000 F for rabbit bladder, and resistances for amphibian skin and bladder much higher than those usually reported. This technique made it possible to observe a transport-related conductance pathway, and a close correlation between transepithelial conductance (G) and short-circuit current (I _sc) in these tight epithelia.G andI _sc were increased by mucosal (Na⁺) [I _sc0 when (Na⁺)0], aldosterone, serosal (HCO ₃ ^– ) and high mucosal (H⁺); were decreased by amiloride, mucosal (Ca⁺⁺), ouabain, metabolic inhibitors and serosal (H⁺); and were unaffected by (Cl^–) and little affected by antidiuretic hormone (ADH). Physiological variation in the rabbits' dietary Na⁺ intake caused variations in bladderG andI _sc similar to those caused by the expectedin vivo changes in aldosterone levels. The relation betweenG andI _sc was the same whether defined by diet changes, natural variation among individual rabbits, or most of the above agents. A method was developed for separately resolving conductances of junctions, basolateral cell membrane, and apical cell membrane from thisG–I _sc relation. Net Na⁺ flux equalledI _sc. Net Cl^– flux was zero on short circuit and equalled only 25% of net Na⁺ flux in open circuit. Bladder membrane fragments contained a Na⁺–K⁺-activated, ouabain-inhibited ATPase. The physiological significance of Na⁺ absorption against steep gradients in rabbit bladder may be to maintain kidney-generated ion gradients during bladder storage of urine, especially when the animal is Na⁺-depleted.     

Effects of aldosterone on Na transport in the toad bladder I. Glycolysis and lactate production under aerobic conditions

Previous studies indicated that aldosterone enhances active Na⁺ transport, glycolysis, lactate production and respiration of the toad bladder. Evidence was also presented that the changes in glycolysis and lactate production were secondary to the changes in active Na⁺ transport. Further analysis of the relationships between metabolism and Na⁺ transport was undertaken with the aid of two inhibitors of pyruvate metabolism, oxythiamine and phenylpyruvate. These inhibitors prevented the aldosterone-induced increase in oxidation of [6-¹⁴C]glucose but had little effect on the increase in lactate production. In contrast, the effect on Na⁺ transport (i.e., I_sc) was completely inhibited by oxythiamine plus phenylpyruvate with glucose as substrate. The effect on Na⁺ transport, however, was obtained wth the by-pass substrates, oxaloacetate plus ß-hydroxybutyrate, in the presence of these inhibitors. These results implied that steroidal enhancement of lactate production and Na⁺ transport were independent effects. To evaluate whether an increase in Na⁺ transport, per se would augment lactate production, the responses were evaluated under conditions of an imposed Na⁺ gradient (mucosal Na⁺ = 5 mM; serosal Na⁺ = 110 mM). Addition of NaCl to the mucosal media evoked the same increase in I_sc as the addition of aldosterone; both additions increased I_sc more than two-fold. Aldosterone reduced lactate production under these conditions while the re-addition of NaCl had no effect on lactate formation. These results are consistent with an action of aldosterone on pathways involved in oxidative energy metabolism, and suggest that the activation of glycolysis may be a function of the net balance between energy production and utilization.     

Effect of 3-isobutyl-1-methylxanthine on HCO3− transport in turtle bladder: Evidence for electrogenic HCO3− secretion

Ouabain-treated turtle bladders bathed on both surfaces by identical HCO₃^?/CO₂-containing, Cl^?-free Na⁺ media exhibit a short-circuit current (I_sc) and transepithelial potential (p.d.) serosa electronegative to mucosa. Addition of 3-isobutyl-1-methylxanthine (IBMX), an inhibitor of cyclic nucleotide phosphodiesterase, rapidly reverses the direction of the I_sc and p.d.. The IBMX-induced reversal of I_sc and p.d. is (1) dependent on the presence of HCO₃^? (and CO₂) in the serosal bathing fluid, (2) independent of Na⁺ and other ions in the bathing medium, (3) decreased by inhibitors of carbonic anhydrase or oxidative metabolism, (4) increased by the serosal addition of cyclic AMP or the disulfonic stilbene, SITS. The results constitute evidence that the reversed I_sc elicited by IBMX represents electrogenic secretion of HCO₃^?.     

Aldosterone regulation of active sodium chloride transport in the lizard colon (Gallotia galloti)

Summary Bioelectrical parameters and unidirectional sodium and chloride fluxes were measured under voltageclamp conditions in groups of lizards submitted to single or chronic aldosterone treatment. Both acute (AT) and chronic (CT) treatment induced significant increases in the short-circuit current (I _sc), as well as in the mucosa-to-serosa (J _m-s ^Na ) and net sodium flux (J _net ^Na ). In AT tissues, aldosterone did not change net chloride flux (J _net ^Cl ) but did so in CT tissues. Amiloride reduced the aldosterone-increased I _sc in AT and CT tissues, inhibited J _net ^Na in AT tissues and abolished it in CT colons. J _net ^Cl was also reduced by the diuretic in the group of AT colons, whereas no changes were observed in the CT tissues. Addition of luminal DIDS reduced Na⁺ absorption and totally inhibited Cl^- absorption in the AT tissues, but did not change I _sc. However, in CT tissues neither Na⁺ nor Cl^- transport were affected by DIDS. A good relationship between I _sc and J _m-s ^Na was apparent after DIDS treatment in AT tissues. In this group, simultaneous addition of DIDS and amiloride totally abolished J _net ^Na and reduced I _sc to untreated control values. Addition of serosal ouabain abolished I _sc and Na⁺ absorption in AT and CT colons, but Cl^- absorption was only altered in AT tissues. These results support the hypothesis that aldosterone induces an electrogenic, amiloride-sensitive sodium absorption, and in a dose-dependent fashion suppresses electroneutral NaCl absorption in the lizard colon.Abbreviations AT acutely treated - CT chronically treated animals - DIDS 4-4-diisothiocyanatostibene-2-2-disulfonic acid - DMSO dimethylsulphoxide - G _t tissue conductance - I _sc short circuit current - PD transepithelial potential difference - SITS 4-acetamido-4-isothiocyanatostilbene-2-2-disulfonic acid - UC untreated controls Preliminary results of this paper were presented at the X ^th meeting of the European Intestinal Transport Group (EITG), Askov Hojskole, Denmark, 16–19 September 1990     

Rapid and specific alterations of goblet cell mucin in rat airway and small intestine associated with resistance against Nippostrongylus brasiliensis reinfection

The intestinal parasitic nematode Nippostrongylus brasiliensis is expelled rapidly from the rat in reinfection challenge compared with that of the primary infection owing to the host defense mechanisms raised against the pre-intestinal- and intestinal-stage larvae. We examined the relationship between the mucin alterations in airway and jejunal mucosae and the worm expulsion after third-stage larva reinfection. When rats had been inoculated with fourth-stage larvae and immunized with only the intestinal-stage worms for more than 8 days, the challenge larvae were expelled during the intestinal stage along with a rapid increase of the specific sialomucin in jejunal mucosa, without any effect on the bronchial mucus. When rats had been infected with third-stage larvae and immunized with only the pre-intestinal stage larvae by killing with antihelminthic, the challenge larvae were rejected during the pre-intestinal stage along with marked goblet cell hyperplasia and Muc5AC mucin hyperproduction on the bronchial mucosa, but not as a result of jejunal mucin alteration. Taking these finding together, immunization with pre-intestinal- and intestinal-stage worms independently increases the airway and intestinal goblet cell mucins, respectively, and in both cases, the mucin alterations may contribute to rapid worm expulsion upon reinfection.     

Nippostrongylus brasiliensis: Peripheral leukocyte responses and correlation of basophils with blood histamine concentration during infection in rats

Rats infected on Day 0 with 3000 infective L₃ larvae of Nippostrongylus brasiliensis, and uninfected controls, were monitored daily through Day 23 postinfection for changes in peripheral leukocytes and blood histamine concentrations. A generalized leukocytosis was observed between Days 7 and 18, the period leading up to and immediately following the time of expulsion of adult worms from the small intestine. The total number of lymphocytes was elevated between Days 11 and 17 post-infection; however, there was no change in the percentage of lymphocytes relative to other white blood cell types. The total number and percentage of monocytes were no different from controls, with the exception of Day 5 postinfection. On that day, there was a significant elevation in the number (614/mm³ blood in infected rats, as compared to 160/mm³ blood in controls) and relative proportion (2.7% of total leukocytes in infected animals, compared to 0.8% in controls) of monocytes, coinciding with the termination of the pulmonary migration of larvae. A period of moderate neutrophilia occurred between Days 7 and 12, but this was not accompanied by any changes in the proportion of neutrophils. A biphasic eosinophil response was observed. An early elevation of eosinophils occurred between Days 3 and 5, corresponding to the period of larval migration through the lungs. A second period of eosinophilia began on Day 11, when worm expulsion was beginning, and continued through Day 19, i.e., beyond the period of worm expulsion. Basophilia was observed as early as Day 6 after infection, rising to a peak on Day 13 (6.8% of total leukocytes in the infected animals, as compared to 0.5% in controls), and declining thereafter, but remaining above control levels until termination of the experiment on Day 23. The histamine content of blood samples, as determined by an enzymic-isotopic assay, closely paralleled the development and decline of basophilia; histamine levels also peaked on Day 13 postinfection (422.5 pg histamine/mm³ blood in infected rats, compared to 66.0 pg histamine/mm³ blood in controls). As basophilia progressed during the course of infection, there was a decline in the amount of histamine per basophil. In uninfected rats and during the first week after infection, basophils contained about 1.5–2.0 pg histamine per cell. In the third week of infection, there was about 0.6 pg histamine per basophil. The time course of the basophilia suggests that these cells may be involved in the expression of immunity to N. brasiliensis.     

Effects of tryptamine on active sodium and chloride transport in the isolated bullfrog cornea

The effects of the serotonin analogue, tryptamine, on the active transepithelial transport of Na⁺ and Cl⁻ in the in vitro bullfrog cornea were studied. Tryptamine, 1 mM, inhibited both the short-circuit current (I_sc) and potential difference (PD) of corneas transporting either Na⁺ alone or both Na⁺ and Cl⁻. The electrical resistance, R, increased in all cases. Both unidirectional Na⁺ and Cl⁻ fluxes were decreased by tryptamine and these changes accounted for the inhibitory effects on the I_sc. The effects of tryptamine were considered along with with those of 2 mM theophylline and 0.1 mM ouabain. Tryptamine inhibited the I_sc and both undirectional Cl⁻ fluxes which were previously stimulated by theophylline. Theophyline addition, after tryptamine preincubation, increased the Cl⁻ undirectional fluxes but did not restore the inhibited I_sc. The inhibitory effects of tryptamine on active Na⁺ and Cl⁻ transport were different from those of ouabain. While both drugs inhibited the forward Na⁺ and Cl⁻ fluxes, their backfluxes decreased with tryptamine and increased with ouabain. The addition to the bathing solution of tryptamine after ouabain preincubation reduced the ouabain-increased backward Cl⁻ flux and further increased the electrical resistance. These results are analyzed in terms of an electrical model from which it appears that tryptamine's mechanism of action was to decrease cellular permeability to the transepithelial movement of Na⁺ and Cl⁻.