Plasma membrane recycling in CFTR-expressing CHO cells

The hypothesis that the cystic fibrosis transmembrane conductance regulator (CFTR) participates in plasma membrane recycling was tested experimentally. Using CHO cells, we determined the effects of CFTR expression and of elevated intracellular cAMP on exocytosis, measured as the incorporation into the plasma membrane of endosomes pre-labelled with biotinylated wheat-germ agglutinin (WGA). CFTR expression was without effect on the rate of exocytosis. Furthermore, cAMP did not affect endosomal recycling to the plasma membrane in either CFTR-expressing or control cells. These findings suggest that CFTR is not involved in regulating plasma membrane recycling in all cells.     

Direct Comparison of NPPB and DPC as Probes of CFTR Expressed in Xenopus Oocytes

Blockers of CFTR with well-characterized kinetics and mechanism of action will be useful as probes of pore structure. We have studied the mechanism of block of CFTR by the arylaminobenzoates NPPB and DPC. Block of macroscopic currents by NPPB and DPC exhibited similar voltage-dependence, suggestive of an overlapping binding region. Kinetic analysis of single-channel currents in the presence of NPPB indicate drug-induced closed time constants averaging 2.2 msec at −100 mV. The affinity for NPPB calculated from single-channel block, K _D = 35 μm, exceeds that for other arylaminobenzoates studied thus far. These drugs do not affect the rate of activation of wild-type (WT) channels expressed in oocytes, consistent with a simple mechanism of block by pore occlusion, and appear to have a single binding site in the pore. Block by NPPB and DPC were affected by pore-domain mutations in different ways. In contrast to its effects on block by DPC, mutation T1134F-CFTR decreased the affinity and reduced the voltage-dependence for block by NPPB. We also show that the alteration of macroscopic block by NPPB and DPC upon changes in bath pH is due to both direct effects (i.e., alteration of voltage-dependence) and indirect effects (alteration of cytoplasmic drug loading). These results indicate that both NPPB and DPC block CFTR by entering the pore from the cytoplasmic side and that the structural requirements for binding are not the same, although the binding regions within the pore are similar. The two drugs may be useful as probes for overlapping regions in the pore. Received: 14 October 1999/Revised: 18 January 2000     

Postnatal development of the brush cells in the common bile duct of the rat

Summary The postnatal development of brush cells in the distal segment of the common bile duct of the rat was examined with respect to cell number and immuno-reactivity for liver fatty acid-binding protein (L-FABP). The brush cells, distinguishable from the principal cells by scanning electron microscopy, first appeared in the common bile duct 4 weeks after birth. They showed a remarkable increase in number, with a sex difference in time, i.e., between 8 and 12 weeks in the male and between 10 and 14 weeks in the female. In both sexes, the frequency of brush cells reached approximately 30% of total epithelial cells by 16 weeks and remained constant until 40 weeks of age. Cells with positive immuno-reactivity for L-FABP first appeared in small numbers at 8 weeks. Immuno-electron microscopy revealed that all immunoreactive cells were brush cells. They increased in number gradually from 16 to 40 weeks with no sex difference. At 40 weeks, the immunoreactive cells reached approximately 7.5% of total epithelial cells, corresponding to one-fourth of the number of brush cells. These results indicate that the occurrence of the brush cell population in the common bile duct is a late event in the postnatal development of the rat and that its functional maturation progresses with aging.     

Reticulum cells in the ontogeny of nasal-associated lymphoid tissue (NALT) in the rat

This study concerns the ontogeny of reticulum cells (RC) in the nasal-associated lymphoid tissue (NALT) of Wistar and Brown-Norway rats. A panel of monoclonal antibodies (mAb) directed against RC in peripheral lymphoid organs (antibodies ED10ED15) was used, together with a recently developed antibody ED17, which recognizes macrophages and Langerhans cells. Early in embryogenesis, staining with common connective tissue markers, ED14 and ED15, was found. ED17-positive cells were present before cells positive to ED1, a pan-macrophage marker, or Ia glycoproteins were observed. The first differentiation of reticulum was seen at the day of birth, when ED10 recognized a distinct area in the nasal mucosa. The first T-lymphocytes were found at the same time. Two days after birth, B-cells and ED11-positive cells were present in the NALT area. Fourteen days after birth, T- and B-cell compartments were recognizable. ED10 was found predominantly in the T-cell area and ED11 was mainly confined to the B-cell compartment. We conclude that the development of the NALT is closely accompanied by the phenotypic specialization of the reticulum. This suggests that the reticulum plays an important role in the compartmentalization of NALT tissue and in the retention of lymphocyte subsets within these compartments.     

Osteogenic inhibition by rat periodontal ligament cells: modulation of bone morphogenic protein-7 activity in vivo

Periodontal ligament width is precisely maintained throughout the lifetime of adult mammals but the biological mechanisms that inhibit ingrowth of bone into this soft connective tissue are unknown. As bone morphogenic proteins strongly stimulate osteogenesis and can induce ectopic bone formation in vivo, we tested the hypothesis that topical application of this powerful osteogenic agent will overwhelm the osteogenic inhibitory mechanisms of periodontal ligament cells and induce ankylosis. Wounds through the alveolar bone and periodontal ligament were created in 45 male Wistar rats. Defects were filled with either a collagen implant or collagen plus bone morphogenic protein (BMP-7), or were left unfilled (controls). Three animals per time period were killed on days 2, 5, 10, 21 and 60 after surgery for each wound type. Cellular proliferation and clonal growth in periodontal tissues were assessed by ³H-thymidine labeling 1 h before death, followed by radioautography. Cellular differentiation of soft and mineralizing connective tissue cell populations was determined by immunohistochemical staining of α-smooth muscle actin, osteopontin and bone sialoprotein. In regenerating periodontium, BMP-7 induced abundant bone formation by 21 days (2.5-fold greater than controls or collagen implant only; P<0.001), but by day 60 the volume of the newly formed bone had returned to baseline levels and was similar for all groups. Independent of the type of treatment, periodontal ligament width was unchanged throughout the experimental period (P>0.05). Animals treated with BMP-7 implants showed greatly increased cellular proliferation in the periodontal ligament adjacent to the wound site and in the regenerating alveolar bone at days 5 and 10 after wounding compared to the other treatment groups (P<0.005). Animals in the BMP-7 group exhibited similar spatial and temporal staining patterns for α-smooth muscle actin, osteopontin and bone sialoprotein as controls. Collectively, these data show that BMP-7 promoted the proliferation of precursor cells in the periodontal ligament but did not induce osteogenic differentiation in this compartment. Consequently a powerful osteogenic stimulus like BMP-7 cannot significantly perturb the mechanisms that regulate periodontal ligament width and maintain periodontal homeostasis. Received: 2 March 1998 / Accepted: 16 June 1998     

Expression of neural cell adhesion molecules,NCAMs, and their polysialylated forms,PSA-NCAMs,in the developing rat pituitary gland

Neural cell adhesion molecules (NCAMs) can undergo post-translational modifications, such as the addition of polysialic acid chains, thus generating PSANCAMs, which are expressed mainly during development. Since polysialylation considerably modifies NCAM adhesivity, expression of NCAMs and PSANCAMs has been investigated in the developing hypophysis by immunohistochemistry. At embryonic day 13 (E13), an antibody against NCAM outlined all cellular profiles in the entire Rathke's pouch; this labelling persisted until adulthood. NCAM expression increased in all lobes during development and concerned all pituitary cell types. In contrast, at E13, PSA-NCAMs were only detected in the neural lobe, solely constituted of pituicytes at this stage, and the tuberal lobe, the only lobe expressing hormonal mRNA at the same stage. PSA-NCAMs expression increased in the neural lobe at E17 with the arrival of the neurosecretory fibres and persisted into adulthood. In the anterior lobe, PSA-NCAMs appeared at E15 where their distribution was similar to that of the differentiating corticotrophic cells; at subsequent stages, their expression extended to the whole anterior lobe. Only two cell types, corticotrophic and somatotrophic cells, remained labelled in the adult gland. In the intermediate lobe, melanotrophic cells never expressed PSA-NCAMs but these were expressed on folliculo-stellate cells at birth, preceding the onset of innervation. These results suggest that NCAMs and PSA-NCAMs play a role in pituitary histogenesis, cell differentiation and neurointermediate lobe innervation.     

内含肽介导的氯离子通道蛋白CFTR的反式剪接

研究利用内含肽(intein)的蛋白质反式剪接功能在大肠杆菌中对囊性纤维化跨膜传导调节因子(cystic fibrosis transmembrane regulator, CFTR)的反式剪接作用.CFTR基因突变导致一种常染色体隐性遗传疾病囊性纤维化(cystic fibrosis, CF).将CFTR的cDNA于剪接反应所需的保守性氨基酸残基Ser-660前断裂为N端和C端,分别与split mini Ssp DnaB 内含肽的106个氨基酸残基的N端和48个氨基酸残基的C端编码序列融合,构建到原核表达载体pBV220 诱导表达后SDS-PAGE可见预期大小剪接形成的CFTR蛋白条带,Western印迹用CFTR特异性抗体进一步证明为剪接所产生的CFTR蛋白,表明内含肽可有效催化CFTR的反式剪接.     

Functional architecture of the CFTR chloride channel

Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), a member of the ATP-binding cassette (ABC) family of membrane transport proteins. CFTR is unique among ABC proteins in that it functions not as an active transporter but as an ATP-gated Cl^? channel. As an ion channel, the function of the CFTR transmembrane channel pore that mediates Cl^? movement has been studied in great detail. On the other hand, only low resolution structural data is available on the transmembrane parts of the protein. The structure of the channel pore has, however, been modeled on the known structure of active transporter ABC proteins. Currently, significant barriers exist to building a unified view of CFTR pore structure and function. Reconciling functional data on the channel with indirect structural data based on other proteins with very different transport functions and substrates has proven problematic. This review summarizes current structural and functional models of the CFTR Cl^? channel pore, including a comprehensive review of previous electrophysiological investigations of channel structure and function. In addition, functional data on the three-dimensional arrangement of pore-lining helices, as well as contemporary hypotheses concerning conformational changes in the pore that occur during channel opening and closing, are discussed. Important similarities and differences between different models of the pore highlight current gaps in our knowledge of CFTR structure and function. In order to fill these gaps, structural and functional models of the membrane-spanning pore need to become better integrated.     

Elongated pericyte-like cells connect discrete capillaries in the cochlear stria vascularis of gerbils and rats

 Bridging structures between discrete capillaries in the stria vascularis of the cochlea were studied morphologically in gerbils and rats. Serial thin sections for transmission electron microscopy revealed (1) that elongated cells surrounded by the basal lamina provided the structural basis for the bridging structure, (2) that the basal lamina surrounding the elongated cell extended to the basal lamina around the capillary endothelial cell, (3) that the electron density of the cytoplasm was similar to that of the pericytes around the capillaries, and (4) that the cell was attached to the capillaries at both ends only. Visualization of the basal lamina by immunofluorescent methods revealed (1) that capillaries were often bent at the site of attachment of the bridging cell, (2) that the bridging cell bifurcated occasionally, and (3) that the density of the bridging cell was much higher in the stria vascularis than in the underlying spiral ligament. Filamentous actin visualized by fluorescent phalloidin was not apparent in the bridging cell. We propose that the bridging cell provides mechanical strength to the tortuous capillary network in the stria vascularis and participates in the specific function of the stria vascularis in cooperation with other types of cells. Received: 26 October 1998 / Accepted: 8 January 1999     

Differential uptake of molecules from the circulation and CSF reveals regional and cellular specialisation in CNS detection of homeostatic signals

The uptake of hydroxystilbamidine (OHSt, FluoroGold equivalent) and wheat germ agglutinin (WGA), into the hypothalamus, two hours after injections into either the circulation or the cerebrospinal fluid, were compared in adult rats. Following intravenous injection, OHSt was found in astrocytes of the median eminence and medial part of the arcuate nucleus whereas WGA intensely labelled the blood vessels and ependymal cells throughout the hypothalamus. In complete contrast, intracerebroventricular (icv) injection into the lateral ventricle resulted in OHSt uptake by ependymocytes and astrocytes in the area adjacent to the third ventricle, with virtually no uptake in regions taking up this dye following systematic injections, i.e., the median eminence and medial arcuate. Following icv injection WGA labelling was intense in all parts of the ependymal layer of the third ventricle, including the α- and β-tanycytes. Injections into the cisterna magna gave a different pattern of uptake with OHSt being found only in astrocytes in the ventral part of the hypothalamus lateral to the arcuate nucleus whilst WGA uptake was virtually absent. This highlights the regional and cellular specialisation for uptake of molecules from the circulation and CSF. The median eminence and medial arcuate take up molecules from the circulation, with different cell types taking up different molecules. As the CSF flows through the ventricular system, different cells lining the ventricular and subarachnoid spaces take up molecules differentially. Molecules in the CSF appear to be excluded from the median eminence and medial arcuate region.This work was supported by the EU Grant QLRT-2001-00826.     

Coupling of ATP Hydrolysis with Channel Gating by Purified, Reconstituted CFTR

The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel situated on the apical membrane of epithelial cells. Our recent studies of purified, reconstituted CFTR revealed that it also functions as an ATPase and that there may be coupling between ATP hydrolysis and channel gating. Both the ATP turnover rate and channel gating are slow, in the range of 0.2 to 1 s^–1, and both activities are suppressed in a disease-causing mutation situated in a putative nucleotide binding motif. Our future studies using purified protein will be directed toward understanding the structural basis and mechanism for coupling between hydrolysis and channel function.     

Secretory granules of hypophyseal and pancreatic endocrine cells contain proteins of the neuronal postsynaptic density

The PDZ domain-containing protein Shank is a master scaffolding protein of the neuronal postsynaptic density and directly or indirectly links neurotransmitter receptors and cell adhesion molecules to the actin-based cytoskeleton. ProSAP/Shank proteins have recently also been detected in several non-neuronal cells in which they are mostly concentrated in the apical subplasmalemmal cytoplasm. In contrast, we have previously reported a more widespread cytoplasmic immunostaining pattern for the ProSAP1/Shank2 protein in endocrine cells at the light-microscopic level. Therefore, in the present study, we have determined the ultrastructural localization of ProSAP1/Shank2 and the ProSAP/Shank-interacting proteins ProSAPiP1 and IRSp53 in pancreatic islet and adenohypophyseal cells by using immunogold staining techniques. Dense immunolabeling of secretory granules including the granule core in cells such as hypophyseal somatotrophs and pancreatic B-cells indicates the unexpected presence of ProSAP/Shank and ProSAP/Shank-interacting proteins in the hormone-storing compartment of endocrine cells. Thus, ProSAP/Shank and certain ProSAP/Shank-interacting proteins exhibit distinct subcellular localizations in the different cell types, raising the possibility that the function of ProSAP/Shank proteins is more diverse than has been envisaged to date. This work was supported by the Deutsche Forschungsgemeinschaft (SFB 497/B8 to J.B. and T.M.B.).     

Gene expression and localization of diacylglycerol kinase isozymes in the rat spinal cord and dorsal root ganglia

The dorsal root ganglion (DRG) and dorsal horn of the spinal cord are areas through which primary afferent information passes enroute to the brain. Previous studies have reported that, during normal neuronal activity, the regional distribution of a second messenger, diacylglycerol (DG), which is derived from phosphoinositide turnover, is diverse in these areas. However, the way that DG is regulated in these organs remains unknown. The present study was performed to investigate mRNA expression and protein localization of DG kinase (DGK) isozymes, which play a central role in DG metabolism. Gene expression for DGK isozymes was detected with variable regional distributions and intensities in the spinal cord. Among the isozymes, most intense signals were found for DGKζ and DGKι in the DRG. By immunohistochemical analysis, DGKζ immunoreactivity was detected heterogeneously in the nucleus and cytoplasm of small DRG neurons with variable levels of distribution, whereas it was detected exclusively in the cytoplasm of large neurons. On the other hand, DGKι immunoreactivity was distributed solely in the cytoplasm of most of the DRG neurons. Double-immunofluorescent imaging of these isozymes showed that they coexisted in a large population of DRG neurons at distinct subcellular sites, i.e., DGKζ in the nucleus and DGKι in the cytoplasm. Thus, DGK isozymes may have different functional roles at distinct subcellular sites. Furthermore, the heterogeneous subcellular localization of DGKζ between the nucleus and cytoplasm implies the possible translocation of this isozyme in small DRG neurons under various conditions.The work was supported by grants-in-aid from the Ministry of Education, Science, Culture, and Sports of Japan (M.T., K.G.) and from the Ono Medical Research Foundation, Kato Memorial Bioscience Foundation, and Janssen Pharmaceutical (K.G.) and by the 21st Century Center of Excellence Program of the Ministry of Education, Culture, Sports, Science and Technology of Japan.     

Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Confers Glibenclamide Sensitivity to Outwardly Rectifying Chloride Channel (ORCC) in Hi-5 Insect Cells

Increasing evidence is now accumulating for the involvement of the cystic fibrosis transmembrane conductance regulator (CFTR) in the control of the outwardly rectifying chloride channel (ORCC). We have examined the sensitivity of ORCC to the sulfonylurea drug glibenclamide in Hi-5 (Trichoplusia ni) insect cells infected with recombinant baculovirus expressing either wild-type CFTR, ΔF508-CFTR or E. coliβ galactosidase cDNA and in control cells either infected with virus alone or uninfected. Iodide efflux and single channel patch-clamp experiments confirmed that forskolin and 1-methyl-3-isobutyl xanthine (IBMX) or 7-methyl-1,3 dipropyl xanthine (DPMX) activate CFTR channels (unitary conductance: 9.1 ± 1.6 pS) only in cells expressing CFTR. In contrast, we identified 4-acetamido-4′-isothiocyanatostilbene-2,2′-disulfonic acid (SITS)-sensitive ORCC in excised membrane patches in any of the cells studied, with similar conductance (22 ± 2.5 pS at −80 mV; 55 ± 4.1 pS at +80 mV) and properties. In the presence of 500 μm SITS, channel open probability (P _o ) of ORCC was reversibly reduced to 0.05 ± 0.01 in CFTR-cells, to 0.07 ± 0.02 in non-CFTR expressing cells and to 0.05 ± 0.02 in ΔF508-cells. In Hi-5 cells that did not express CFTR, glibenclamide failed to inhibit ORCC activity even at high concentrations (100 μm), whereas 500 μm SITS reversibly inhibited ORCC. In contrast in cells expressing CFTR or ΔF508, glibenclamide dose dependently (IC₅₀= 17 μm, Hill coefficient 1.2) and reversibly inhibited ORCC. Cytoplasmic application of 100 μm glibenclamide reversibly reduced P _o from 0.88 ± 0.03 to 0.09 ± 0.02 (wash: P _o = 0.85 ± 0.1) in CFTR cells and from 0.89 ± 0.05 to 0.08 ± 0.05 (wash: P _o = 0.87 ± 0.1) in ΔF508 cells. In non-CFTR expressing cells, glibenclamide (100 μm) was without effect on P _o (control: P _o = 0.89 ± 0.09, glib.: P _o = 0.86 ± 0.02; wash: P _o = 0.87 ± 0.05). These data strongly suggest that the expression of CFTR confers glibenclamide sensitivity to the ORCC in Hi-5 cells. Received: 23 October 1998/Revised: 29 December 1998     

Carbonic anhydrase and neuronal enzymes in cultured glomus cells of the carotid body of the rat

Summary The cellular localization of carbonic anhydrase (CAH) in the carotid body of the rat was investigated by means of Hansson's cobalt-precipitation technique in cultures of dissociated cells. In both young (2-day-old) and old (77-day-old) cultures, the parenchymal glomus (type-I) cells were selectively stained by this technique, and in addition expressed tyrosine hydroxylase and neuron-specific enolase as revealed by immunofluorescence. Enzymic reaction product of CAH appeared to be predominantly intracellular since staining was more intense and occurred more rapidly following permeabilization of the cell membranes with Triton X-100; its formation was inhibited by the CAH-inhibitor acetazolamide (1–10 M) or by increasing the pH from 5.8 to 7.5. Cryostat sections of the carotid bifurcation revealed intense CAH-reaction product in cell clusters of the carotid body, in a few cells of the nodose ganglion, and in red blood cells. Neuronal cell bodies of the petrosal ganglion and superior cervical ganglion (SCG) were largely non-reactive. The SCG is known to contain clusters of small intensely fluorescent (SIF) cells, which were also non-reactive when grown in dissociated cell culture. Thus, although glomus and SIF cells are often considered to be similar cell types, functional CAH-activity appears unique to glomus cells, and this may be important for the physiological response of the carotid body to certain chemosensory stimuli.     

Immunohistochemical localization of the eosinophil major basic protein in the uterus horn and cervix of the rat at term and after parturition

Summary Distribution of the eosinophil major basic protein (MBP) was studied in the rat uterus horn and cervix by means of immunohistochemistry using an antiserum raised against rat MBP. Various hormonal contexts were investigated: pre- and post-parturition, the estrous cycle, and ovariectomy followed by hormonal treatment or without treatment. MBP was detectable in the cervix as early as 12 h post-partum, appearing in the stroma close to the myometrium. The MBP had spread throughout the stroma toward the luminal epithelium after a few days. In contrast, no MBP was seen in sections of the corresponding pre- and post-partum uteri and in the pre-partum cervix. In cycling rats, MBP was distributed equally in the cervix and uterus and was more abundant during proestrus and estrus. In ovariectomized rats and in ovariectomized rats subsequently treated with progesterone, no MBP was detected in the cervix or uterus. In the cervix of ovariectomized rats treated with estradiol, MBP first appeared in the muscle layer situated between the two cervical lumina and then reached the stroma; within a few days only the stroma was stained. Inversely, in the uterus MBP-staining first appeared in the stroma. In conclusion, analysis of the distribution of MBP in rat uterus revealed a marked difference in the response of the cervix and horn to a hormonal environment.     

A Mathematical Model of the Pancreatic Ductal Epithelium

A mathematical model of the HCO⁻ ₃-secreting pancreatic ductal epithelium was developed using network thermodynamics. With a minimal set of assumptions, the model accurately reproduced the experimentally measured membrane potentials, voltage divider ratio, transepithelial resistance and short-circuit current of nonstimulated ducts that were microperfused and bathed with a CO₂/HCO⁻ ₃-free, HEPES-buffered solution, and also the intracellular pH of duct cells bathed in a CO₂/HCO⁻ ₃-buffered solution. The model also accurately simulated: (i) the effect of step changes in basolateral K⁺ concentration, and the effect of K⁺ channel blockers on basolateral membrane potential; (ii) the intracellular acidification caused by a Na⁺-free extracellular solution and the effect of amiloride on this acidification; and (iii) the intracellular alkalinization caused by a Cl⁻-free extracellular solution and the effect of DIDS on this alkalinization. In addition, the model predicted that the luminal Cl⁻ conductance plays a key role in controlling both the HCO⁻ ₃ secretory rate and intracellular pH during HCO⁻ ₃ secretion. We believe that the model will be helpful in the analysis of experimental data and improve our understanding of HCO⁻ ₃-transporting mechanisms in pancreatic duct cells. Received: 18 October 1995/Revised: 5 July 1996     

Differential Effects of Aldosterone and Vasopressin on Chloride Fluxes in Transimmortalized Mouse Cortical Collecting Duct Cells

The effects of aldosterone and vasopressin on Cl⁻ transport were investigated in a mouse cortical collecting duct (mpkCCD) cell line derived from a transgenic mouse carrying the SV40 large T antigen driven by the proximal regulatory sequences of the L-pyruvate kinase gene. The cells had features of a tight epithelium and expressed the amiloride-sensitive sodium channel and the cystic fibrosis transmembrane conductance regulator (CFTR) genes. dD-arginine vasopressin (dDAVP) caused a rapid, dose-dependent, increase in short-circuit current (I _sc ). Experiments with ion channel blockers and apical ion substitution showed that the current represented amiloride-sensitive Na⁺ and 5-nitro-2-(3-phenylpropylamino)benzoate-sensitive and glibenclamide-sensitive Cl⁻ fluxes. Aldosterone (5 × 10⁻⁷ m for 3 or 24 hr) stimulated I _sc and apical-to-basal ²²Na⁺ flux by 3-fold. ³⁶Cl⁻ flux studies showed that dDAVP and aldosterone stimulated net Cl⁻ reabsorption and that dDAVP potentiated the action of aldosterone on Cl⁻ transport. Whereas aldosterone affected only the apical-to-basal ³⁶Cl⁻ flux, dDAVP mainly increased the apical-to-basal Cl⁻ flux and the basal-to-apical flux of Cl⁻ to a lesser extent. These results suggest that the discrete dDAVP-elicited Cl⁻ secretion involves the CFTR and that dDAVP and aldosterone may affect in different ways the observed increased Cl⁻ reabsorption in this model of mouse cultured cortical collecting duct cells. Received: 8 January 1998/Revised: 25 March 1998     

Lymphoid and non-lymphoid cells in nasal-associated lymphoid tissue (NALT) in the rat

Summary Lymphocyte and macrophage subpopulations and the stroma of mucosa-associated lymphoid tissue in the nasal cavity of the rat were examined by application of immunohistochemical and enzyme histochemical methods to cryostat sections. Nasal-associated lymphoid tissue was composed of a loose reticular network with lymphocytes and macrophages, covered by epithelium. The epithelium was infiltrated with B cells, T helper (W3/13-positive) and T suppressor/cytotoxic or large granular cells (OX8-positive), ED1-positive macrophages and Ia-positive cells. The B cell areas were populated by B cells, immunopositive for surface IgM or IgG. B cells with surface IgA or IgE were rare. Germinal centres were found infrequently. T helper cells were scattered throughout the B cell area. A few ED1-positive macrophages and ED5-positive follicular dendritic cells were observed. Strong Ia staining (mostly of B cells) was found in this area. The T cell areas contained T helper and T suppressor/cytotoxic cells in about equal amounts, and numerous ED1-positive macrophages. ED1 staining was also found in the subepithelial area. Numerous ED1-, ED2- and ED3-positive macrophages were found in the border between the lymphoid mass and the surrounding connective tissue. A few non-lymphoid cells showed weak acid phosphatase or non-specific esterase activity. The morphological observations suggest that nasal-associated lymphoid tissue plays an important role in the first contact with inhaled antigens.