Triple immunofluorescence staining with antibodies raised in the same species to study the complex innervation pattern of intrapulmonary chemoreceptors

Antibody elution with 2-me/SDS solution: Uses for multi-layer immunohistochemical analysis of wholemount preparations of human colonic myenteric plexus

Indirect immunofluorescence is usually restricted to 3-5 markers per preparation, limiting analysis of coexistence. A solution containing 2-mercaptoethanol and sodium dodecyl sulfate (2-ME/SDS) can elute indirect immunofluorescence labelling (i.e. primary antisera followed by fluorophore-conjugated secondary antisera) and has been used for sequential staining of sections. The aim of this study was to test whether 2-ME/SDS is effective for eluting indirect immunofluorescent staining (with primary antisera visualised by fluorophore-coupled secondary antisera) in wholemount preparations. We also analysed how 2-ME/SDS may work and used this understanding to devise additional uses for immunofluorescence in the nervous system. 2-ME/SDS appears to denature unfixed proteins (including antisera used as reagents) but has much less effect on antigenicity of formaldehyde-fixed epitopes. Moieties linked by strong biotin-streptavidin bonds are highly resistant to elution by 2-ME/SDS. Two primary antisera raised in the same species can be applied without spurious cross-reactivity, if a specific order of labelling is followed. The first primary antiserum is followed by a biotinylated secondary, then a tertiary of fluorophore-conjugated streptavidin. The preparation is then exposed to 2-ME/SDS, which has minimal impact on labelling by the first primary/secondary/tertiary combination. However, when this is followed by a second primary antiserum (raised in the same species), followed by a fluorophore-conjugated secondary antiserum, the intervening 2-ME/SDS exposure prevents cross-reactivity between primary and secondary antisera of the two layers. A third property of 2-ME/SDS is that it reduces lipofuscin autofluorescence, although it also raises background fluorescence and strongly enhances autofluorescence of erythrocytes. In summary, 2-ME/SDS is easy to use, cost-effective and does not require modified primary antisera. It can be used as the basis of a multi-layer immunohistochemistry protocol and allows 2 primary antisera raised in the same species to be used together.

Multiple Immunostainings with Different Epitope Retrievals—The FOLGAS Protocol

We describe a sequential multistaining protocol for immunohistochemistry, immunofluorescence and CyTOF imaging for formalin-fixed, paraffin-embedded specimens (FFPE) in the formalin gas-phase (FOLGAS), enabling sequential multistaining, independent from the primary and secondary antibodies and retrieval. Histomorphologic details are preserved, and crossreactivity and loss of signal intensity are not detectable. Combined with a DAB-based hydrophobic masking of metal-labeled primary antibodies, FOLGAS allows the extended use of CyTOF imaging in FFPE sections.

Serotonin Expression in the Song Circuitry of Adult Male Zebra Finches

Serotonin is an important neurotransmitter of the brain, but its role in song control remains to be fully demonstrated. Using male zebra finches (Taeniopygia guttata) that have song learning and production capabilities, we analysed the serotonin expression levels in the song nuclei and adjacent areas (peri-song nuclei) using immunohistochemistry. Key song nuclei were identified using combinations of Hoechst, choline acetyltransferase, and a neurofilament (NN18) marker in reference to the ZEBrA atlas. Mean serotonin expression was highest in interfacial nucleus (Nif) and lower in the other song nuclei in the following order (in order of highest first): interfacial nucleus (Nif) > Area X > dorsomedial part of the intercollicular nucelus (DM) > robust nucleus of the archistriatum (RA) > lateral magnocellular nucleus of the anterior neostriatum (LMAN) > ventral respiratory group (VRG) > dorsolateral nucleus of the medial thalamus (DLM) > the nucleus HVC (proper name) > tracheosyringeal motor nucleus (nXIIts). However, the mean serotonin expression (in order of highest first) in the peri-song nuclei regions was: peri-DM > peri-nXIIts > supra-peri-HVC > peri-RA > peri-DLM > peri-Area X > infra-peri-HVC > peri-VRG > peri-LMAN > peri-Nif. Interestingly, serotoninergic fibers immunostained for serotonin or the serotonin transporter can be found as a basket-like peri-neuronal structure surrounding cholinergic cell bodies, and appear to form contacts onto dopaminergic neurones. In summary, serotonin fibers are present at discrete song nuclei, and peri-song nuclei regions, which suggest serotonin may have a direct and/or modulatory role in song control.

Mixed Multiplex Staining: Automated RNAscope™ and OPAL™ for Multiple Targets

The application of multiplex immunofluorescent detection of proteins, mRNAs, or both in combination has contributed to our understanding of biomarker expression and distribution within normal and pathological diseased tissues. In combination with whole-slide scanning these techniques permit the visualization of multiple biomarkers, their distribution within normal and pathological tissues, and their spatial and proximal distribution to each other in intact tissue sections. The expression of multiple biomarkers can now be used to accurately phenotype specific cell types, e.g., immune cells which rely on the expression of multiple biomarkers for precise identification. The availability of antibody reagents to detect specific protein targets, range of targets in specific technology platforms, and tissue fixation may mean that one technology may not be suitable for visualizing all biomarkers of interest. Here I demonstrate that a mixed multiplex approach for multiple protein and mRNA can be delivered on automated platforms suitable for high-throughput environments, and predict that mixed multiplex approaches will be important in future to compensate for tissue fixation differences, biomarker availability, and technology platform limitations.

Opposing Gradients of MicroRNA Expression Temporally Pattern Layer Formation in the Developing Neocortex

The precisely timed generation of different neuronal types is a hallmark of development from invertebrates to vertebrates. In the developing mammalian neocortex, neural stem cells change competence over time to sequentially produce six layers of functionally distinct neurons. Here, we report that microRNAs (miRNAs) are dispensable for stem-cell self-renewal and neuron production but essential for timing neocortical layer formation and specifying laminar fates. Specifically, as neurogenesis progresses, stem cells reduce miR-128 expression and miR-9 activity but steadily increase let-7 expression, whereas neurons initially maintain the differences in miRNA expression present at birth. Moreover, miR-128, miR-9, and let-7 are functionally distinct; capable of specifying neurons for layer VI and layer V and layers IV, III, and II, respectively; and transiently altering their relative levels of expression can modulate stem-cell competence in a neurogenic-stage-specific manner to shift neuron production between earlier-born and later-born fates, partly by temporally regulating a neurogenesis program involving Hmga2.

Differential Innervation of Secretory Coils and Ducts in Human Eccrine Sweat Glands

BACKGROUND

Previous studies demonstrate that eccrine sweat glands are innervated by both cholinergic and adrenergic nerves. However, it is still unknown whether the secretory coils and ducts of eccrine sweat glands are equally innervated by the sympathetic nerve fibers. To well understand the mechanisms on sweat secretion and reabsorption, the differential innervation of secretory coils and ducts in human eccrine sweat glands was investigated in the study.

METHODS

From June 2016 to June 2017, six human skins were fixed, paraffin-embedded, and cut into 5 μm-thick sections, followed by costaining for nerve fiber markers protein gene product 9.5 (PGP 9.5), tyrosine hydroxylase (TH) and vasoactive intestinal peptide (VIP), and eccrine sweat gland markers K7, S100P, and K14 by combining standard immunofluorescence with tyramide signal amplification (IF-TSA). Stained sections were observed under the microscope, photographed, and analyzed.

RESULTS

The fluorescent signals of PGP 9.5, TH, and VIP were easily visualized, by IF-TSA, as circular patterns surrounding eccrine sweat glands, but only PGP 9.5 could be observed by standard IF. The IF-TSA method is more sensitivity than standard IF in detecting antigens expressed at low levels. PGP 9.5, TH, and VIP appeared primarily surrounding the secretory coils and sparsely surrounding the sweat ducts.

CONCLUSION

Sweat secretion is mainly controlled by autonomic nerves whereas sweat reabsorption is less affected by nerve activity.

Targeting fatty acid amide hydrolase and transient receptor potential vanilloid-1 simultaneously to modulate colonic motility and visceral sensation in the mouse: A pharmacological intervention with N-arachidonoyl-serotonin (AA-5-HT)

BACKGROUND

Endocannabinoid anandamide (AEA) inhibits intestinal motility and visceral pain, but it may also be proalgesic through transient receptor potential vanilloid-1 (TRPV1). AEA is degraded by fatty acid amide hydrolase (FAAH). This study explored whether dual inhibition of FAAH and TRPV1 reduces diarrhea and abdominal pain.

METHODS

Immunostaining was performed on myenteric plexus of the mouse colon. The effects of the dual FAAH/TRPV1 inhibitor AA-5-HT on electrically induced contractility, excitatory junction potential (EJP) and fast (f) and slow (s) inhibitory junction potentials (IJP) in the mouse colon, colonic propulsion and visceromotor response (VMR) to rectal distension were studied. The colonic levels of endocannabinoids and fatty acid amides were measured.

KEY RESULTS

CB1-positive neurons exhibited TRPV1; only some TRPV1 positive neurons did not express CB1. CB1 and FAAH did not colocalize. AA-5-HT (100 nM-10 μM) decreased colonic contractility by ~60%; this effect was abolished by TRPV1 antagonist 5'-IRTX, but not by CB1 antagonist, SR141716. AA-5-HT (1 μM-10 μM) inhibited EJP by ~30% and IJPs by ~50%. The effects of AA-5-HT on junction potentials were reversed by SR141716 and 5`-IRTX. AA-5-HT (20 mg/kg; i.p.) inhibited colonic propulsion by ~30%; SR141716 but not 5`-IRTX reversed this effect. AA-5-HT decreased VMR by ~50%-60%; these effects were not blocked by SR141716 or 5`-IRTX. AA-5-HT increased AEA in the colon.

CONCLUSIONS AND INFERENCES

The effects of AA-5-HT on visceral sensation and colonic motility are differentially mediated by CB1, TRPV1 and non-CB1/TRPV1 mechanisms, possibly reflecting the distinct neuromodulatory roles of endocannabinoid and endovanilloid FAAH substrates in the mouse intestine.

Fluorescence Analysis of Vitamin D Receptor Status of Circulating Tumor Cells (CTCS) in Breast Cancer: From Cell Models to Metastatic Patients

The Vitamin D receptor (VDR) expressed in normal breast tissue and breast tumors has been suggested as a new prognostic biomarker in breast cancer (BC). Besides, increasing evidence supports the view that the detection of circulating tumor cells (CTCs) predicts outcome in early and metastatic BC. Consequently, an evaluation of VDR expression in the CTCs of BC patients may allow optimization of their treatment. As an attempt to profile and subtype the CTCs of metastatic patients, we established an innovative fluorescence technique using nine BC cell lines to visualize, define, and compare their individual VDR status. Afterwards, we tested the CTC presence and VDR expression in blood samples (cytospins) collected from 23 metastatic BC patients. The results demonstrated major differences in the VDR levels among the nine cell lines, and VDR positive CTCs were detected in 46% of CTC-positive patients, with a total of 42 CTCs individually analyzed. Due to the limited number of patients in this study, no correlation between VDR expression and BC subtype classification (according to estrogen receptor (ER), progesterone receptor (PR) and HER2) could be determined, but our data support the view that VDR evaluation is a potential new prognostic biomarker to help in the optimization of therapy management for BC patients.

(Uncommon) Mechanisms of Branchial Ammonia Excretion in the Common Carp (Cyprinus carpio) in Response to Environmentally Induced Metabolic Acidosis

Freshwater fishes generally increase ammonia excretion in acidic waters. The new model of ammonia transport in freshwater fish involves an association between the Rhesus (Rh) protein Rhcg-b, the Na(+)/H(+) exchanger (NHE), and a suite of other membrane transporters. We tested the hypothesis that Rhcg-b and NHE3 together play a critical role in branchial ammonia excretion in common carp (Cyprinus carpio) chronically exposed to a low-pH environment. Carp were exposed to three sequential environmental treatments-control pH 7.6 water (24 h), pH 4.0 water (72 h), and recovery pH 7.6 water (24 h)-or in a separate series were simply exposed to either control (72 h) or pH 4.0 (72 h) water. Branchial ammonia excretion was increased by ∼2.5-fold in the acid compared with the control period, despite the absence of an increase in the plasma-to-water partial pressure NH3 gradient. Alanine aminotransferase activity was higher in the gills of fish exposed to pH 4 versus control water, suggesting that ammonia may be generated in gill tissue. Gill Rhcg-b and NHE3b messenger RNA levels were significantly elevated in acid-treated relative to control fish, but at the protein level Rhcg-b decreased (30%) and NHE3b increased (2-fold) in response to water of pH 4.0. Using immunofluorescence microscopy, NHE3b and Rhcg-b were found to be colocalized to ionocytes along the interlamellar space of the filament of control fish. After 72 h of acid exposure, Rhcg-b staining almost disappeared from this region, and NHE3b was more prominent along the lamellae. We propose that ammoniagenesis within the gill tissue itself is responsible for the higher rates of branchial ammonia excretion during chronic metabolic acidosis. Unexpectedly, gill Rhcg-b does not appear to be important in gill ammonia transport in low-pH water, but the strong induction of NHE3b suggests that some NH4(+) may be eliminated directly in exchange for Na(+). These findings contrast with previous studies in larval zebrafish (Danio rerio) and medaka (Oryzias latipes), underlining the importance of species comparisons.

Effects of GnRH immunization on the reproductive axis and thymulin

The bidirectional regulation of thymulin in the reproductive-endocrine function of the hypothalamic-pituitary-gonadal (HPG) axis of rats immunized against GnRH remains largely unclear. We explored the alterations in hormones in the HPG axis in immunized rats to dissect the repressive effect of immunization on thymulin, and to clarify the interrelation of reproductive hormones and thymulin in vivo. The results showed that, in the first 2 weeks of booster immunization, thymulin was repressed when reproductive hormones were severely reduced. The self-feedback regulation of thymulin was then stimulated in later immune stages: the rising circulating thymulin upregulated LH and FSH, including GnRH in the hypothalamus, although the levels of those hormones were still significantly lower than in the control groups. In astrocytes, thymulin produced a feedback effect in regulated GnRH neurons. However, in the arcuate nucleus (Arc) and the median eminence (ME), the mediator of astrocytes and other glial cells were also directly affected by reproductive hormones. Thus, in immunized rats, the expression of glial fibrillary acidic protein was distinctly stimulated in the Arc and ME. This study demonstrated that thymulin was downregulated by immunization against GnRH in early stage. Subsequently, the self-feedback regulation was provoked by low circulating thymulin. Thereafter, rising thymulin levels promoted pituitary gonadotropins levels, while acting directly on GnRH neurons, which was mediated by astrocytes in a region-dependent manner in the hypothalamus.

Registration of whole immunohistochemical slide images: an efficient way to characterize biomarker colocalization

BACKGROUND AND OBJECTIVE

Extracting accurate information from complex biological processes involved in diseases, such as cancers, requires the simultaneous targeting of multiple proteins and locating their respective expression in tissue samples. This information can be collected by imaging and registering adjacent sections from the same tissue sample and stained by immunohistochemistry (IHC). Registration accuracy should be on the scale of a few cells to enable protein colocalization to be assessed.

METHODS

We propose a simple and efficient method based on the open-source elastix framework to register virtual slides of adjacent sections from the same tissue sample. We characterize registration accuracies for different types of tissue and IHC staining.

RESULTS

Our results indicate that this technique is suitable for the evaluation of the colocalization of biomarkers on the scale of a few cells. We also show that using this technique in conjunction with a sequential IHC labeling and erasing technique offers improved registration accuracies.

DISCUSSION

Brightfield IHC enables to address the problem of large series of tissue samples, which are usually required in clinical research. However, this approach, which is simple at the tissue processing level, requires challenging image analysis processes, such as accurate registration, to view and extract the protein colocalization information.

CONCLUSIONS

The method proposed in this work enables accurate registration (on the scale of a few cells) of virtual slides of adjacent tissue sections on which the expression of different proteins is evidenced by standard IHC. Furthermore, combining our method with a sequential labeling and erasing technique enables cell-scale colocalization.

Activation of CB1 inhibits NGF-induced sensitization of TRPV1 in adult mouse afferent neurons

Transient receptor potential vanilloid 1 (TRPV1)-containing afferent neurons convey nociceptive signals and play an essential role in pain sensation. Exposure to nerve growth factor (NGF) rapidly increases TRPV1 activity (sensitization). In the present study, we investigated whether treatment with the selective cannabinoid receptor 1 (CB1) agonist arachidonyl-2'-chloroethylamide (ACEA) affects NGF-induced sensitization of TRPV1 in adult mouse dorsal root ganglion (DRG) afferent neurons. We found that CB1, NGF receptor tyrosine kinase A (trkA), and TRPV1 are present in cultured adult mouse small- to medium-sized afferent neurons and treatment with NGF (100ng/ml) for 30 min significantly increased the number of neurons that responded to capsaicin (as indicated by increased intracellular Ca(2 +) concentration). Pretreatment with the CB1 agonist ACEA (10nM) inhibited the NGF-induced response, and this effect of ACEA was reversed by a selective CB1 antagonist. Further, pretreatment with ACEA inhibited NGF-induced phosphorylation of AKT. Blocking PI3 kinase activity also attenuated the NGF-induced increase in the number of neurons that responded to capsaicin. Our results indicate that the analgesic effect of CB1 activation may in part be due to inhibition of NGF-induced sensitization of TRPV1 and also that the effect of CB1 activation is at least partly mediated by attenuation of NGF-induced increased PI3 signaling.

Elution of High-affinity (>10-9 KD) Antibodies from Tissue Sections: Clues to the Molecular Mechanism and Use in Sequential Immunostaining

Inconsistent results obtained with published methods for the elution of antibodies from tissue sections prompted the assessment of both old and new methods in combination with monoclonal rabbit antibodies of known, increased affinity (above 1×10(-9) KD). We tested an acidic (pH 2) glycine buffer, a 6 M urea hot buffer and a 2-Mercaptoethanol, SDS buffer (2-ME/SDS). Some antibodies were not removed by the glycine pH 2 or 6 M urea hot buffers, indicating that antibodies survive much harsher conditions than previously believed. We found that the elution is dependent upon the antibody affinity and is reduced by species-specific crosslinking via a dimeric or Fab fragments of a secondary antibody. The high affinity bond of exogenous streptavidin with the endogenous biotin can be removed by 6 M urea but not by the other buffers. 2-ME/SDS buffer is superior to glycine pH 2 and 6 M urea hot elution buffers for all antibodies because of its irreversible effect on the structure of the antibodies. It also has a mild retrieving effect on some antigens present on routinely treated sections and no detrimental effect on the immunoreactivity of the tissue. Therefore, 2-ME/SDS buffer is the method of choice to perform multiple rounds of immunostaining on a single routine section.

Stain-Decolorize-Stain (SDS): a new technique for multiple staining

Multiple staining of more than one gene/antigen on a single tissue section is an indispensable tool in cell and tissue research. However, most of the available multiple staining techniques have limitations, and there has been no technique to simultaneously visualize and distinguish tissue antigens, nucleotide sequences and other chemical compounds on the same slide. Here, we present a practical and economic multiple stain technique, with which multiple cellular components including mRNA (with in situ hybridization), antigen epitope (with immunohistochemistry) and chemical molecules (with histochemistry) can be stained on a single tissue section to study their relationship. In addition, this technique also offers the possibility to evaluate morphology with an H&E staining on the same sections. We used the placenta, pancreas, breast ductal carcinoma, colon adenocarcinoma, cerebellum, tonsil and heart tissue sections to evaluate the applicability of this new technique. The sensitivity and specificity of the technique have been tested, and an optimal protocol is recommended. Its applications in surgical pathology and research are discussed. This technique offers a novel tool to evaluate the relationship among multiple components at the same or adjacent locations to meet the needs of pathology diagnosis and research.

Rapid and sensitive detection of Escherichia coli O157:H7 in milk and ground beef using magnetic bead-based immunoassay coupled with tyramide signal amplification

Escherichia coli O157:H7 is a major foodborne pathogen that has posed serious problems for food safety and public health. Recent outbreaks and recalls associated with various foods contaminated by E. coli O157:H7 clearly indicate its deleterious effect on food safety. A rapid and sensitive detection assay is needed for this harmful organism to prevent foodborne illnesses and control outbreaks in a timely manner. We developed a magnetic bead-based immunoassay for detection of E. coli O157:H7 (the most well-known Shiga toxigenic E. coli strain) with a 96-well microplate as an assay platform. Immunomagnetic separation (IMS) and tyramide signal amplification were coupled to the assay to increase its sensitivity and specificity. This immunoassay was able to detect E. coli O157:H7 in pure culture with a detection limit of 50 CFU/ml in less than 3 h without an enrichment step. The detection limit was decreased 10-fold to 5 CFU/ml with addition of a 3-h enrichment step. When this assay was tested with other nontarget foodborne pathogens and common enteric bacteria, no cross-reactivity was found. When tested with artificially contaminated ground beef and milk samples, the assay sensitivity decreased two- to fivefold, with detection limits of 250 and 100 CFU/ml, respectively, probably because of the food matrix effect. The assay results also were compared with those of a sandwich-type enzyme-linked immunosorbent assay (ELISA) and an ELISA coupled with IMS; the developed assay was 25 times and 4 times more sensitive than the standard ELISA and the IMS-ELISA, respectively. Tyramide signal amplification combined with IMS can improve sensitivity and specificity for detection of E. coli O157:H7. The developed assay could be easily adapted for other foodborne pathogens and will contribute to improved food safety and public health.

Effects of period RNAi on V-ATPase expression and rhythmic pH changes in the vas deferens of Spodoptera littoralis (Lepidoptera: Noctuidae)

Circadian clocks (oscillators) regulate multiple aspects of insect behaviour and physiology. The circadian system located in the male reproductive tract of Lepidoptera orchestrates rhythmic sperm release from testis and sperm maturation in the upper vas deferens (UVD). Our previous research on the cotton leafworm, Spodoptera littoralis, suggested rhythmic changes in the V-ATPase levels in the UVD epithelium, which correlated with rhythmic pH fluctuations in the UVD lumen. However, it was not known whether UVD cells contain clock mechanism that generates these daily fluctuations. In the current paper, we show circadian rhythm in the expression of clock gene period at the mRNA and protein level in the UVD epithelium. To determine the role of PER in V-ATPase and pH regulation, testes-UVD complexes were treated in vitro with double-stranded fragments of per mRNA (dsRNA). This treatment, which transiently lowered per mRNA and protein in the UVD, altered expression of V-ATPase c subunit. In addition, per RNAi caused a significant delay in the UVD lumen acidification. These data demonstrate that the UVD molecular oscillator involving the period gene plays an essential role in the regulation of rhythmic V-ATPase activity and periodic acidification of the UVD lumen.

Differential molecular profiles of astrocytes in degeneration and re-innervation after sensory deafferentation of the adult rat cochlear nucleus

Ablating the cochlea causes total sensory deafferentation of the cochlear nucleus. Over the first postoperative week, degeneration of the auditory nerve and its synaptic terminals in the cochlear nucleus temporally overlaps with its re-innervation by axon collaterals of medial olivocochlear neurons. At the same time, astrocytes increase in size and density. We investigated the time courses of the expression of ezrin, polysialic acid, matrix metalloprotease-9 and matrix metalloprotease-2 within these astrocytes during the first week following cochlear ablation. All four proteins are known to participate in degeneration, regeneration, or both, following injury of the central nervous system. In a next step, stereotaxic injections of kainic acid were made into the ventral nucleus of the trapezoid body prior to cochlear ablation to destroy the neurons that re-innervate the deafferented cochlear nucleus by axon collaterals developing growth-associated protein 43 immunoreactivity. This experimental design allowed us to distinguish between molecular processes associated with degeneration and those associated with re-innervation. Under these conditions, astrocytic growth and proliferation showed an unchanged deafferentation-induced pattern. Similarly, the distribution and amount of ezrin and matrix metalloprotease-9 in astrocytes after cochlear ablation developed in the same way as under cochlear ablation alone. In sharp contrast, the astrocytic expression of polysialic acid and matrix metalloprotease-2 normally invoked by cochlear ablation collapsed when re-innervation of the cochlear nucleus was inhibited by lesioning medial olivocochlear neurons with kainic acid. In conclusion, re-innervation, including axonal growth and synaptogenesis, seems to prompt astrocytes to recompose their molecular profile, paving the way for tissue reorganisation after nerve degeneration and loss of synaptic contacts.

Expression of transcription factor Satb2 in adult mouse brain

Previous investigations on the expression and function of special AT-rich sequence binding protein 2 (Satb2) are largely limited to the cerebral cortex. Here, we explore the expression of Satb2 thoroughly by immunohistochemistry in the adult mouse central nervous system (CNS). Besides the cerebral cortex, we found that Satb2 is specifically expressed in the bed nucleus of the stria terminalis, horizontal limb of the diagonal band, lateral hypothalamic area, arcuate nucleus, hypothalamic paraventricular nucleus, ventral tegmental nucleus, laterodorsal tegmental nucleus, dorsal raphe nucleus, rostral periolivary region, and parabrachial nucleus. Double immunostaining showed that Satb2 is exclusively expressed in the excitatory neurons of neocortex. In addition, Satb2 is specifically expressed in A12 group of hypothalamic dopaminergic neurons and in serotonergic neurons in the dorsal part of the dorsal raphe nucleus. Our results present a comprehensive overview of Satb2 expression in the adult brain and provide insights for studying the role of Satb2 in the mature CNS.

Simultaneous visualization of myosin heavy chain isoforms in single muscle sections

We developed a staining protocol that enables simultaneous visualization of myosin heavy chain (MHC) pure and hybrid muscle fiber types in rat skeletal muscle. Up to eight different muscle fiber types can be visualized in a single section of the rat extensor digitorum longus muscle, which contains all four adult MHC isoforms and shows plasticity during the denervation-reinnervation process. Triple immunofluorescent staining of MHC-1, MHC-2a and MHC-2b with primary antibodies BA-D5 (isotype IgG2b), SC-71 (isotype IgG1) and BF-F3 (isotype IgM) and with three fluorophore-labeled isotype-specific secondary antibodies displays different muscle fiber types in a merged image of red, green and blue channels, each in its own color. Immunoperoxidase staining with primary antibody 6H1 directed against MHC-2x can be additionally applied on the same tissue section to facilitate the identification of muscle fibers containing MHC-2x. Triple staining can also be used in combination with other staining procedures to derive more information about the number of capillaries or the oxidative potential of muscle fiber types. Simultaneous visualization of multiple fiber types in a single merged image enables economical use of muscle samples and provides simple and rapid identification of all fiber types that are present in rat limb muscles.

Heterogeneity of ERα and ErbB2 Status in Cell Lines and Circulating Tumor Cells of Metastatic Breast Cancer Patients

Hormone therapy and anti-ErbB2 therapies are prescribed according to the hormone receptor [estrogen receptor α (ERα)/progesterone receptor] and ErbB2 status of the initial tumor, but it appears that circulating tumor cells (CTCs) and, consequently, the metastatic cells may have a different receptor status. As an attempt to meet the crucial need for identification of the subpopulation of patients that will benefit from more individualized therapies, rapidly evolving therapies should allow a profiling of the tumors and/or of the CTCs. We established a triple fluorescence staining using eight cell lines to visualize the CTCs (cytokeratin detection) and then to define their individual ERα and ErbB2 status. Afterward, we used this method for blood samples from 26 metastatic breast cancer patients. We identified major differences of ERα levels between the cell lines and even within one cell line. For the metastatic patients, we detected and characterized CTCs in 38.5% of the patients with a total of 92 CTCs. We could demonstrate that at least 69.6% of the CTCs exhibit an ERα and/or ErbB2 status different from the status of the primary tumor and that the CTCs from only 30% of the patients had no change of receptor status. Strikingly, heterogeneities of the status, aggregation, and size clearly appear within the CTCs. The data we generated outline the importance of a profiling not only of tumors but also of CTCs to establish individualized treatments. CTCs may then appear as new prognosis and treatment marker for both metastatic and adjuvant breast cancers.

Notch signaling differentially regulates the cell fate of early endocrine precursor cells and their maturing descendants in the mouse pancreas and intestine

Notch signaling inhibits differentiation of endocrine cells in the pancreas and intestine. In a number of cases, the observed inhibition occurred with Notch activation in multipotential cells, prior to the initiation of endocrine differentiation. It has not been established how direct activation of Notch in endocrine precursor cells affects their subsequent cell fate. Using conditional activation of Notch in cells expressing Neurogenin3 or NeuroD1, we examined the effects of Notch in both organs, on cell fate of early endocrine precursors and maturing endocrine-restricted cells, respectively. Notch did not preclude the differentiation of a limited number of endocrine cells in either organ when activated in Ngn3(+) precursor cells. In addition, in the pancreas most Ngn3(+) cells adopted a duct but not acinar cell fate; whereas in intestinal Ngn3(+) cells, Notch favored enterocyte and goblet cell fates, while selecting against endocrine and Paneth cell differentiation. A small fraction of NeuroD1(+) cells in the pancreas retain plasticity to respond to Notch, giving rise to intraislet ductules as well as cells with no detectable pancreatic lineage markers that appear to have limited ultrastructural features of both endocrine and duct cells. These results suggest that Notch directly regulates cell fate decisions in multipotential early endocrine precursor cells. Some maturing endocrine-restricted NeuroD1(+) cells in the pancreas switch to the duct lineage in response to Notch, indicating previously unappreciated plasticity at such a late stage of endocrine differentiation.

Benefits and pitfalls of secondary antibodies: why choosing the right secondary is of primary importance

Simultaneous labeling of multiple targets in a single sample, or multiplexing, is a powerful approach to directly compare the amount, localization and/or molecular properties of different targets in the same sample. Here we highlight the robust reliability of the simultaneous use of multiple mouse monoclonal antibodies (mAbs) of different immunoglobulin G (IgG) subclasses in a wide variety of multiplexing applications employing anti-mouse IgG subclass-specific secondary antibodies (2°Abs). We also describe the unexpected finding that IgG subclass-specific 2°Abs are superior to general anti-mouse IgG 2°Abs in every tested application in which mouse mAbs were used. This was due to a detection bias of general anti-mouse IgG-specific 2°Abs against mAbs of the most common mouse IgG subclass, IgG1, and to a lesser extent IgG2b mAbs. Thus, when using any of numerous mouse mAbs available through commercial and non-profit sources, for cleaner and more robust results each mAb should be detected with its respective IgG subclass-specific 2°Ab and not a general anti-mouse IgG-specific 2°Ab.

G protein-coupled receptors in the hypothalamic paraventricular and supraoptic nuclei--serpentine gateways to neuroendocrine homeostasis

G protein-coupled receptors (GPCRs) are the largest family of transmembrane receptors in the mammalian genome. They are activated by a multitude of different ligands that elicit rapid intracellular responses to regulate cell function. Unsurprisingly, a large proportion of therapeutic agents target these receptors. The paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus are important mediators in homeostatic control. Many modulators of PVN/SON activity, including neurotransmitters and hormones act via GPCRs--in fact over 100 non-chemosensory GPCRs have been detected in either the PVN or SON. This review provides a comprehensive summary of the expression of GPCRs within the PVN/SON, including data from recent transcriptomic studies that potentially expand the repertoire of GPCRs that may have functional roles in these hypothalamic nuclei. We also present some aspects of the regulation and known roles of GPCRs in PVN/SON, which are likely complemented by the activity of 'orphan' GPCRs.

Alveolar epithelial CNGA1 channels mediate cGMP-stimulated, amiloride-insensitive, lung liquid absorption

Impairment of lung liquid absorption can lead to severe respiratory symptoms, such as those observed in pulmonary oedema. In the adult lung, liquid absorption is driven by cation transport through two pathways: a well-established amiloride-sensitive Na(+) channel (ENaC) and, more controversially, an amiloride-insensitive channel that may belong to the cyclic nucleotide-gated (CNG) channel family. Here, we show robust CNGA1 (but not CNGA2 or CNGA3) channel expression principally in rat alveolar type I cells; CNGA3 was expressed in ciliated airway epithelial cells. Using a rat in situ lung liquid clearance assay, CNG channel activation with 1 mM 8Br-cGMP resulted in an approximate 1.8-fold stimulation of lung liquid absorption. There was no stimulation by 8Br-cGMP when applied in the presence of either 100 μM L: -cis-diltiazem or 100 nM pseudechetoxin (PsTx), a specific inhibitor of CNGA1 channels. Channel specificity of PsTx and amiloride was confirmed by patch clamp experiments showing that CNGA1 channels in HEK 293 cells were not inhibited by 100 μM amiloride and that recombinant αβγ-ENaC were not inhibited by 100 nM PsTx. Importantly, 8Br-cGMP stimulated lung liquid absorption in situ, even in the presence of 50 μM amiloride. Furthermore, neither L: -cis-diltiazem nor PsTx affected the β(2)-adrenoceptor agonist-stimulated lung liquid absorption, but, as expected, amiloride completely ablated it. Thus, transport through alveolar CNGA1 channels, located in type I cells, underlies the amiloride-insensitive component of lung liquid reabsorption. Furthermore, our in situ data highlight the potential of CNGA1 as a novel therapeutic target for the treatment of diseases characterised by lung liquid overload.

Mammalian target of rapamycin signaling in the spinal cord is required for neuronal plasticity and behavioral hypersensitivity associated with neuropathy in the rat

The protein kinase mammalian target of rapamycin (mTOR) regulates mRNA translation and is inhibited by rapamycin. Signaling pathways involving mTOR are implicated in physiological and pathophysiological processes. We determined the spinal effects of the rapamycin analogue cell cycle inhibitor (CCI)-779 on neuronal responses and behavioral hypersensitivity in a model of persistent neuropathic pain. We also assessed the anatomical distribution of spinal mTOR signaling pathways. Specifically, we ligated rat spinal nerves L5 and L6 to produce a model of neuropathic pain. After confirming neuropathy with behavioral testing, we obtained in vivo single-unit extracellular stimulus-evoked recordings from deep dorsal horn spinal neurons. We applied CCI-779 spinally in electrophysiological and behavioral studies and assessed its effects accordingly. We also used immunohistochemistry to probe for mTOR signaling pathways in dorsal root ganglia (DRG) and the spinal cord. We found that spinally administered CCI-779 rapidly attenuated calibrated mechanically but not thermally evoked neuronal responses and mechanically evoked behavioral responses. Immunohistochemistry showed presence of mTOR signaling pathways in nociceptive-specific C-fiber DRG and in neurons of inner lamina II of the spinal cord. We conclude that alterations in the activity of spinal mTOR signaling pathways are crucial to the full establishment of spinal neuronal plasticity and behavioral hypersensitivity associated with nerve injury.

Perspective

This study is consistent with growing evidence implicating mTOR signaling pathways as important modulators of persistent pain, providing novel insights into the molecular mechanisms of pain maintenance and potential for novel approaches into treating chronic pain.

Troubleshooting tissue specificity and antibody selection: Procedures in immunohistochemical studies

Optimal antigen detection and identification is dependent on the tissue of interest, the method of fixation, processing, and antibody specificity. We evaluated specific antigens in frozen middle cerebral artery (MCA) sections from rat brains under various conditions of fixation and differing primary and secondary antibody concentrations. Fresh MCAs were frozen, cryosectioned (8 microm), and adhered to chrom-alum coated slides. The effects of different fixation and antigen retrieval/pretreatments were tested for detection of enzymes and receptors involved in MCA tone regulation. Antigen localization was determined with specific primary antibodies and detected using fluorochrome-conjugated secondary antibodies. Spatial distribution of localized antigens was imaged using confocal microscopy. Frozen sections preserved the morphology of the endothelium and/or vessel wall within the tissue in a manner comparable to formalin-fixed sections. Fixation and tissue processing methods were modified based on the primary antibody used. Optimal antigen detection was obtained using fixatives such as 4% paraformaldehyde, 100% acetone or 100% methanol. Pretreatments, such as 1% SDS, enzymatic digestion using 0.1% trypsin, or application of heat were used to optimize antigen-antibody interaction. Stringent background and control checks were performed to ensure specificity of staining in both single and multiple labeling techniques. In a research setting where epitope detection is not used for diagnostic purposes, there is more latitude in tissue fixation. Frozen samples offer a more versatile method of linking the appropriate fixation and tissue processing to the primary antibody's unique needs. At the same time, it stabilizes the tissue in a format that allows for later analysis of multiple antigens with specific detection requirements in same tissue.

Cannabinoid-1 (CB1) receptors regulate colonic propulsion by acting at motor neurons within the ascending motor pathways in mouse colon

Cannabinoid-1 (CB(1)) receptors on myenteric neurons are involved in the regulation of intestinal motility. Our aim was to investigate CB(1) receptor involvement in ascending neurotransmission in mouse colon and to characterize the involved structures by functional and morphological means. Presence of the CB(1) receptor was investigated by RT-PCR, and immunohistochemistry was used for colabeling studies. Myenteric reflex responses were initiated by electrical stimulation (ES) at different distances, and junction potentials (JP) were recorded from circular smooth muscle cells by intracellular recording in an unpartitioned and a partitioned recording chamber. In vivo colonic propulsion was tested in wild-type and CB(1)(-/-) mice. Immunostaining with the cytoskeletal marker peripherin showed CB(1) immunoreactivity both on Dogiel type I and type II neurons. Further neurochemical characterization revealed CB(1) on choline acetyltransferase-, calretinin-, and 5-HT-immunopositive myenteric neurons, but nitrergic neurons appeared immunonegative for CB(1) immunostaining. Solitary spindle-shaped CB(1)-immunoreactive cells in between smooth muscle cells lacked specific markers for interstitial cells of Cajal or glial cells. ES elicited neuronally mediated excitatory JP (EJP) and inhibitory JP. Gradual increases in distance resulted in a wave-like EJP with EJP amplitudes being maximal at the location of stimulating electrode 6 and a maximal EJP projection distance of approximately 18 mm. The CB(1) receptor agonist WIN 55,212-2 reduced the amplitude of EJP and was responsible for shortening the oral spreading of the excitatory impulse. In a partitioned chamber, WIN 55,212-2 reduced EJP at the separated oral sites, proving that CB(1) activation inhibits interneuron-mediated neurotransmission. These effects were absent in the presence of the CB(1) antagonist SR141716A, which, when given alone, had no effect. WIN 55,212-2 inhibited colonic propulsion in wild-type mice but not in SR141716A-pretreated wild-type or CB(1)(-/-) mice. Activation of the CB(1) receptor modulates excitatory cholinergic neurotransmission in mouse colon by reducing amplitude and spatial spreading of the ascending electrophysiological impulses. This effect on electrophysiological spreading involves CB(1)-mediated effects on motor neurons and ascending interneurons and is likely to underlie the here reported in vivo reduction in colonic propulsion.

Functional live cell imaging of the pulmonary neuroepithelial body microenvironment

Pulmonary neuroepithelial bodies (NEBs) are densely innervated groups of neuroendocrine cells invariably accompanied by Clara-like cells. Together with NEBs, Clara-like cells form the so-called "NEB microenvironment," which recently has been assigned a potential pulmonary stem cell niche. Conclusive data on the nature of physiological stimuli for NEBs are lacking. This study aimed at developing an ex vivo mouse lung vibratome slice model for confocal live cell imaging of physiological reactions in identified NEBs and surrounding epithelial cells. Immunohistochemistry of fixed slices demonstrated that NEBs are almost completely shielded from the airway lumen by tight junction-linked Clara-like cells. Besides the unambiguous identification of NEBs, the fluorescent dye 4-Di-2-ASP allowed microscopic identification of ciliated cells, Clara cells, and Clara-like cells in live lung slices. Using the mitochondrial uncoupler FCCP and a mitochondrial membrane potential indicator, JC-1, increases in 4-Di-2-ASP fluorescence in NEB cells and ciliated cells were shown to represent alterations in mitochondrial membrane potential. Changes in the intracellular free calcium concentration ([Ca2+](i)) in NEBs and surrounding airway epithelial cells were simultaneously monitored using the calcium indicator Fluo-4. Application (5 s) of 50 mM extracellular potassium ([K+](o)) evoked a fast and reproducible [Ca2+](i) increase in NEB cells, while Clara-like cells displayed a delayed (+/- 4 s) [Ca2+](i) increase, suggestive of an indirect, NEB-mediated activation. The presented approach opens interesting new perspectives for unraveling the functional significance of pulmonary NEBs in control lungs and disease models, and for the first time allows direct visualization of local interactions within the NEB microenvironment.

Multiple immunoenzyme staining: methods and visualizations for the observation with spectral imaging

Several staining concepts and color combinations exist to perform successful double immunoenzyme staining on human tissue specimens. Most of these concepts are based on differences between both primary antibodies: animal species, mouse Ig isotype or IgG subclasses, conjugates, or concentrations. Traditionally, double immunoenzyme staining has used chromogens selected to provide maximum color contrast when observed with the unaided eye. Unfortunately, visually good color combinations always include at least one diffuse chromogen, because of the paucity of appropriate chromogen colors. This situation is drastically changed with the use of spectral imaging, where multicolor microscopy can be unmixed in individual images based on their spectral characteristics. Spectral unmixing can be performed even up to quadruple immunoenzyme staining. This work contains practical suggestions for immunoenzyme double staining procedures for some frequently encountered primary antibody combinations: rabbit-mouse, goat-mouse, mouse-mouse, and rabbit-rabbit. The suggested protocols are all suitable for a classical red-brown color combination plus blue nuclear counterstain that is composed of peroxidase activity (diaminobenzidine tetrahydrochloride), alkaline phosphatase activity (Liquid Permanent Red), and hematoxylin, respectively. Although the red and brown chromogens do not contrast very well visually, they both show a crisp localization and can be perfectly unmixed by spectral imaging.

Pulmonary expression of voltage-gated calcium channels: special reference to sensory airway receptors

Studying depolarisation induced calcium entry in our recently developed in situ lung slice model for molecular live cell imaging of selectively visualised pulmonary neuroepithelial bodies (NEBs), exemplified the need for information on the localisation of voltage-gated calcium channels (Ca(v)) in lungs in general, and related to sensory airway receptors more specifically. The present study therefore aimed at identifying the expression pattern of all major classes and subtypes of Ca(v) channels, using multiple immunostaining of rat lung cryosections. Ca(v) channel antibodies were combined with antibodies that selectively label NEBs, nerve fibre populations, smooth muscle, endothelium and Clara cells. Ca(v)2.1 (P/Q-type) was the only Ca(v) channel expressed in NEB cell membranes, and appeared to be restricted to the apical membrane of the slender NEB cell processes that reach the airway lumen. Subpopulations of the vagal but not the spinal sensory nerve fibres that contact NEBs showed immunoreactivity (IR) for Ca(v)1.2 (L-type) and Ca(v)2.1. Ca(v)2.3 (R-type) was selectively expressed by the so-called Clara-like cells that cover NEBs only, and appears to be a unique marker to discriminate this epithelial cell type from the much more extensive group of Clara cells in rat airways. The laminar nerve endings of smooth muscle-associated airway receptors (SMARs) revealed IR for both Ca(v)2.1 and Ca(v)2.2 (N-type). More generally, Ca(v)1.2 was seen to be expressed in vascular smooth muscle, Ca(v)2.3 and Ca(v)3.1 (T-type) in bronchial smooth muscle, Ca(v)3.1 and Ca(v)3.2 (T-type) in endothelial cells, and Ca(v)1.3 (L-type) in a limited number of epithelial cells. In conclusion, the present immunocytochemical study has demonstrated that the various subtypes of Ca(v) channels have distinct expression patterns in rat lungs. Special focus on morphologically/neurochemically characterised sensory airway receptors learned us that both NEBs and SMARs present Ca(v) channels. Knowledge of the identification and localisation of Ca(v) channels in airway receptors and surrounding tissues provides a solid basis for interpretation of the calcium mediated activation studied in our ex vivo lung slice model.

Selective visualisation of sensory receptors in the smooth muscle layer of ex-vivo airway whole-mounts by styryl pyridinium dyes

Recently, we established the location, morphology and neurochemical coding of vagal smooth-muscle-associated airway receptors (SMARs) in rat lungs. These receptors were characterised as branching laminar terminals that originated from myelinated nerve fibres and were intercalated between airway smooth-muscle bundles. To allow the direct physiological examination of these receptors, the present investigation aimed at visualising SMARs in airway whole-mounts of rat and mouse lungs ex vivo. Short incubation with various styryl pyridinium dyes (AM1-43, FM2-10, FM4-64 or 4-Di-2-ASP) gave a highly selective fluorescent visualisation of both laminar nerve terminals and myelinated fibres from which they originated throughout the intrapulmonary airway tree in mouse and in rat. The reliable and specific labelling of SMARs ex vivo with these lipophilic membrane dyes was confirmed via immunostaining for protein gene-product 9.5 and vesicular glutamate transporters. Similar to the intrapulmonary location of NEBs, these SMARs appeared to be even more explicitly located near airway bifurcations. Both the trachealis muscle and the smooth-muscle bundles of extrapulmonary bronchi were also shown to contain laminar nerve terminals that were morphologically similar to the SMARs reported in the intrapulmonary airways. Thus, this study provides an in-vitro model enabling, for the first time, the fast and reliable visualisation of SMARs and the myelinated nerve fibres from which they originate in airway whole-mount preparations ex vivo. As such, this model opens up further perspectives and creates a valid basis for direct physiological measurement and manipulation of the individually identified airway receptors.

Sensory Receptors in the Visceral Pleura

Today, diagnosis and treatment of chest pain related to pathologic changes in the visceral pleura are often difficult. Data in the literature on the sensory innervation of the visceral pleura are sparse. The present study aimed at identifying sensory end-organs in the visceral pleura, and at obtaining more information about neurochemical coding. The immunocytochemcial data are mainly based on whole mounts of the visceral pleura of control and vagally denervated rats. It was shown that innervation of the rat visceral pleura is characterized by nerve bundles that enter in the hilus region and gradually split into slender bundles with a few nerve fibers. Separate nerve fibers regularly give rise to characteristic laminar terminals. Because of their unique association with the elastic fibers of the visceral pleura, we decided to refer to them as "visceral pleura receptors" (VPRs). Cryostat sections of rat lungs confirmed a predominant location on mediastinal and interlobar lung surfaces. VPRs can specifically be visualized by protein gene product 9.5 immunostaining, and were shown to express vesicular glutamate transporters, calbindin D28K, Na+/K+-ATPase, and P2X3 ATP-receptors. The sensory nerve fibers giving rise to VPRs appeared to be myelinated and to have a spinal origin. Because several of the investigated proteins have been reported as markers for sensory terminals in other organs, the present study revealed that VPRs display the neurochemical characteristics of mechanosensory and/or nociceptive terminals. The development of a live staining method, using AM1-43, showed that VPRs can be visualized in living tissue, offering an interesting model for future physiologic studies.

Six-colour fluorescent imaging of lymphoid tissue based on colour addition theory

Multi-colour imaging of immunofluorescently labelled tissue using confocal microscopy was accomplished by using colour addition theory. This new technique includes several improvements for immunolabelling: (1) the co-localization of two or more markers on one cell for the identification of specific cell populations; (2) the co-localization of two fluorescent dyes from secondary reagents for the identification of the cells; (3) a multi-step staining protocol with two primary antibodies originating from the same host species or with two or three biotin-conjugated primary antibodies. After image acquisition, colour segmentation/unmixing are applied to the single multi-colour image to generate multi-pseudo-channels for individual or co-localized fluorescent dyes. With this new technique, we have been able to visualize six cell populations simultaneously in the mouse lymph node and intestine. The efficiency of this method has also been demonstrated in the three-dimensional reconstruction of thick sections from mouse ileum. Our method is simple, efficient, and may be indispensable in experimental cell and tissue studies requiring multiple immunolabelling.

Sensory receptors in the airways: neurochemical coding of smooth muscle-associated airway receptors and pulmonary neuroepithelial body innervation

Mainly due to the lack of conclusive morphological data, correlation between functionally and morphologically defined lung receptors has so far been unsatisfactory. In the present study, multiple immunocytochemical stainings with a panel of markers for (mechanso)sensory nerve fibres were performed in order to visualise putative receptor terminals in rat intrapulmonary airways. We first focussed on determining the location, morphology and neurochemical coding of subepithelial receptor-like structures that have been sporadically reported in the wall of large diameter airways. Immunostaining with antibodies against Na+/K+-ATPase alpha3, vesicular glutamate transporter 1 (VGLUT1) and VGLUT2 revealed branching laminar subepithelial receptor endings associated with airway smooth muscle. The latter nerve terminals appeared to further express calbindin D28k (CB), and the ATP receptor P2X3, but were calcitonin gene-related peptide (CGRP)-negative. The nerve fibres that give rise to these terminals were shown to be myelinated and have a vagal sensory origin. Because of the close association between the laminar terminals of this receptor-like structures and airway smooth muscle, we will further refer to these clearly morphologically identifiable sensory end organs as 'smooth muscle-associated airway receptors (SMARs)'. Secondly, we further explored the sensory innervation of pulmonary neuroepithelial bodies (NEBs). NEBs are intraepithelial groups of neuroendocrine cells, contacted by several nerve fibre populations, at least three of which are sensory. The spinal sensory innervation of NEBs expresses CGRP and substance P, contacts NEBs at their basal pole, and is capsaicin-sensitive. The intraepithelial vagal sensory innervation of NEBs, on the other hand, appears to be myelinated and could be labelled by antibodies against VGLUT1, VGLUT2, CB and P2X3 receptors. Na+/K+-ATPase alpha3 immunostaining additionally labelled part of the vagal sensory innervation of rat pulmonary NEBs. The neurochemical coding and receptor-like appearance of SMARs and of the complex vagal sensory innervation of NEBs appeared to be almost identical and reminiscent of mechanosensors. Both SMARs and vagal nodose nerve terminals in NEBs therefore likely represent the morphological counterparts of subgroups of the extensive population of physiologically characterised myelinated vagal airway receptors, the majority of which are mechanosensitive. Electrophysiological data based on 'local' stimuli should be interpreted with caution, because of the regular close apposition of SMARs and NEBs and the very similar characteristics of their nerve terminals.

Neurochemical characterisation of sensory receptors in airway smooth muscle: comparison with pulmonary neuroepithelial bodies

Descriptions of morphologically well-defined sensory airway receptors are sparse, in contrast to the multiplicity of airway receptors that have been identified electrophysiologically. The present study aimed at further determining the location, morphology and neurochemical coding of subepithelial receptor-like structures that have been sporadically reported in the wall of large diameter airways. The results were compared with those obtained for pulmonary neuroepithelial bodies (NEBs), which are complex intraepithelial sensory airway receptors. Multiple immunocytochemical staining showed branching laminar subepithelial receptor-like endings, which were found to intercalate in the smooth muscle layer of intrapulmonary conducting airways in rats. Because of the consistent intimate association with the airway smooth muscle, the laminar terminals will further be referred to as 'smooth muscle-associated airway receptors (SMARs)'. SMARs were characterised by their Na(+)/K(+)-ATPase alpha3, vesicular glutamate transporter 1 (VGLUT1) and VGLUT2-immunoreactivity, expression of the ATP receptor P2X(3), and the presence of calcium-binding proteins. Nerve fibres giving rise to SMARs were shown to be myelinated and to have a vagal origin. Interestingly, the neurochemical coding and receptor-like appearance of SMARs appeared to be almost identical to at least part of the complex vagal sensory terminals in NEBs. Intraepithelial nerve endings in pulmonary NEBs were indeed also shown to originate from myelinated vagal afferent nerve fibres, and to express Na(+)/K(+)-ATPase alpha3, VGLUT1, VGLUT2, P2X(3) and calcium-binding proteins. Since several of the latter proteins have been reported as markers for mechanoreceptor terminals in other organs, both SMARs and the vagal nodose nerve terminals in NEBs seem good candidates to represent the morphological counterparts of at least subsets of the extensive population of physiologically characterised myelinated vagal airway mechanoreceptors. The observation that SMARs and NEBs are regularly found in each other's immediate neighbourhood, and the very similar characteristics of their nerve terminals, point out that the interpretation of electrophysiological data based on 'local' stimuli should be made with great caution.

Energy homeostasis and gastrointestinal endocrine differentiation do not require the anorectic hormone peptide YY

The gastrointestinal hormone peptide YY is a potent inhibitor of food intake and is expressed early during differentiation of intestinal and pancreatic endocrine cells. In order to better understand the role of peptide YY in energy homeostasis and development, we created mice with a targeted deletion of the peptide YY gene. All intestinal and pancreatic endocrine cells developed normally in the absence of peptide YY with the exception of pancreatic polypeptide (PP) cells, indicating that peptide YY expression was not required for terminal differentiation. We used recombination-based cell lineage trace to determine if peptide YY cells were progenitors for gastrointestinal endocrine cells. Peptide YY(+) cells gave rise to all L-type enteroendocrine cells and to islet partial differential and PP cells. In the pancreas, approximately 40% of pancreatic alpha and rare beta cells arose from peptide YY(+) cells, suggesting that most beta cells and surprisingly the majority of alpha cells are not descendants of peptide YY(+)/glucagon-positive/insulin-positive cells that appear during early pancreagenesis. Despite the anorectic effects of exogenous peptide YY(3-36) following intraperitoneal administration, mice lacking peptide YY showed normal growth, food intake, energy expenditure, and responsiveness to peptide YY(3-36). These observations suggest that targeted disruption of the peptide YY gene does not perturb terminal endocrine cell differentiation or the control of food intake and energy homeostasis.

A multicolor fluorescence immunostaining technique for simultaneous antigen targeting

A general problem in immunocytochemistry is the development of a reliable multiple immunolabeling method with primary antibodies originating from the same host species. Here, we briefly outline different approaches intended to close this technological gap and focus on multiple immunolabeling with monoclonal primary antibodies. To this end, we generated a basic universal protocol for the use of secondary antibodies selectively recognizing different isotypes/subclasses of monoclonal primary antibodies. This approach is widely applicable and offers a simple procedure for simultaneously detecting two or more antigens.

Application of antigen retrieval by heating for double-label fluorescent immunohistochemistry with identical species-derived primary antibodies

Double-label fluorescent immunohistochemistry (IHC) is frequently used to identify cellular and subcellular co-localization of independent antigens. In general, primary antibodies for double labeling should be derived from independent species. However, such convenient pairs of antibodies are not always available. To overcome this problem, several methods for double labeling with primary antibodies from identical species have been proposed. Among them are methods using monovalent secondary antibodies, such as Fab fragments. Soluble immune complexes consisting of primary and monovalent secondary antibodies are first formed. After absorption of the excess secondary antibody with nonspecific immunoglobulin, the immune complexes are applied to sections. By this procedure, unwanted cross-reaction between false pairs of antibodies is avoidable. However, soluble immune complexes often show reduced or no immunoreactivity to antigens on sections. I noted that antigen retrieval (AR) of tissues by heating often but not always showed improved immunoreactivity for soluble immune complexes. Here I demonstrate the examination of conditions for this soluble immune complex method using AR-treated sections and show examples of double-label fluorescent IHC with identical species-derived primary antibodies.

Primary antibody-Fab fragment complexes: a flexible alternative to traditional direct and indirect immunolabeling techniques

Immunolabeling with immune complexes of primary and secondary antibodies offers an attractive method for detecting and quantifying specific antigen. Primary antibodies maintain their affinity for specific antigen after labeling with Fab fragments in vitro. Incubation of these immune complexes with excess normal serum from the same species as the primary antibody prevents free Fab fragments from recognizing immunoglobulin. Effectively a hybrid between traditional direct and indirect immunolabeling techniques, this simple technique allows primary antibodies to be non-covalently labeled with a variety of reporter molecules as and when required. Using complexes containing Fab fragments that recognize both the Fc and F(ab')2 regions of IgG, we show that this approach prevents nonspecific labeling of endogenous immunoglobulin, can be used to simultaneously detect multiple antigens with primary antibodies derived from the same species, and allows the same polyclonal antibody to be used for both antigen capture and detection in ELISA.

Neurogenin 3-expressing progenitor cells in the gastrointestinal tract differentiate into both endocrine and non-endocrine cell types

Mice deficient for the transcription factor neurogenin 3 (ngn3) fail to develop endocrine cells in the intestine and pancreas and show partial endocrine differentiation in the stomach. We expressed Cre recombinase under control of a ngn3 BAC to achieve high fidelity cell lineage tracing in vivo to determine whether endocrine cells in these organs differentiate from NGN3+ precursor cells. Our results indicate that all small intestinal enteroendocrine cells arise from ngn3-expressing cells and confirm that NGN3+ cells give rise to all pancreatic endocrine cells as noted previously. By examining mice at a developmental stage when all of the cell types in the stomach have differentiated, we have delineated region-associated differences in endocrine differentiation. A much smaller fraction of endocrine cells populating the acid-producing region of the stomach is derived from NGN3+ precursor in contrast to the antral-pyloric region. Unexpectedly, ngn3 is expressed in cells that adopt non-endocrine cell fates including significant fractions of goblet and Paneth cells in the intestine and a small number of duct and acinar cells in the pancreas. Rarely, ngn3 was expressed in pluripotent cells in intestinal crypts with resultant labeling of an entire crypt-villus unit. Thus, ngn3 expression occurs in mixed populations of immature cells that are not irreversibly committed to endocrine differentiation.

Coexistence of non-adrenergic non-cholinergic inhibitory and excitatory neurotransmitters in a large neuronal subpopulation in the vaginal segment of the chicken oviduct

The presence, distribution and smooth muscle motor effects of galanin and pituitary adenylate cyclase activating peptide (PACAP) were studied in the nerves of the vaginal part of the oviduct of egg-laying hens. Galanin and PACAP immunoreactivity were found both in neuronal perikarya and nerve fibres within the wall of the vaginal segment. Both populations showed a similar distribution pattern. Particularly the circular muscle and the intramural vascular net were richly innervated. A few galanin- and PACAP-IR nerve fibres extended up to the mucosal folds. Multiple labelling showed galanin to be colocalised with PACAP as well as with vasoactive intestinal polypeptide (VIP) and nitric oxide synthase (NOS) in a large, partly intrinsic neuronal subpopulation innervating the smooth muscle wall. Pharmacological in vitro experiments showed that isolated vaginal muscle strips had a spontaneous basal activity that was not affected by the neuronal conductance blocker tetrodotoxin (TTX). Galanin induced concentration-dependent contractions that were TTX-insensitive. PACAP, VIP, nitric oxide (NO) and the NO donor nitroglycerin caused concentration-dependent relaxations that were TTX-insensitive. Electrical field stimulation of isolated muscle strips induced frequency-dependent relaxations that were blocked by TTX and reduced by the NOS blocker L-nitroarginine. These data provide evidence that the vaginal part of the oviduct contains a largely intrinsic, neuronal subpopulation, capable of releasing multiple non-adrenergic, non-cholinergic (NANC) motor agents for the control of local muscular activities. In addition, we provided pharmacological evidence that VIP, NO and PACAP exert an inhibitory and galanin an excitatory action on isolated muscle strips of the vaginal part of the chicken oviduct. Our results suggest that these NANC neurotransmitters play an important role in the regulation of neuromuscular activity in this region.

Cannabinoid receptor type 1 modulates excitatory and inhibitory neurotransmission in mouse colon

The effects of cannabinoid receptor agonists and antagonists on smooth muscle resting membrane potentials and on membrane potentials following electrical neuronal stimulation in a myenteric neuron/smooth muscle preparation of wild-type and cannabinoid receptor type 1 (CB1)-deficient mice were investigated in vitro. Double staining for CB1 and nitric oxide synthase (neuronal) was performed to identify the myenteric CB1-expressing neurons. Focal electrical stimulation of the myenteric plexus induced a fast (f) excitatory junction potential (EJP) followed by a fast and a slow (s) inhibitory junction potential (IJP). Treatment of wild-type mice with the endogenous CB1 receptor agonist anandamide reduced EJP while not affecting fIJP and sIJP. EJP was significantly higher in CB1-deficient mice than in wild-type littermate controls, and anandamide induced no effects in CB1-deficient mice. N-arachidonoyl ethanolamide (anandamide), R-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3,-de]- 1,4-benzoxazin-6-yl]-1-naphtalenylmethanone, a synthetic CB1 receptor agonist, nearly abolished EJP and significantly reduced the fIJP in wild-type mice. N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-caroxamide (SR141716A), a CB1-specific receptor antagonist, was able to reverse the agonist effects induced in wild-type mice. SR141716A, when given alone, significantly increased EJP in wild-type mice without affecting IJP in wild-type and EJP in CB1-deficient mice. Interestingly, SR141716A reduced fIJP in CB1-deficient mice. In the mouse colon, nitrergic myenteric neurons do not express CB1, implying that CB1 is expressed in cholinergic neurons, which is in line with the functional data. Finally, excitatory and inhibitory neurotransmission in the mouse colon is modulated by activation of CB1 receptors. The significant increase in EJP in CB1-deficient mice strongly suggests a physiological involvement of CB1 in excitatory cholinergic neurotransmission.

Quantification of neuroepithelial bodies and their innervation in fawn-hooded and Wistar rat lungs

The Fawn-Hooded rat (FHR), a model for primary pulmonary hypertension, shows an unexplained hypersensitivity to airway hypoxia. Because pulmonary neuroepithelial bodies (NEBs) appear to express a functional oxygen-sensing mechanism and an extensive sensory innervation, possible changes in this system should be taken into consideration. In the present study a comparative analysis of NEBs and their selective innervation was performed in FHRs and Wistar control rats. In both rat strains, the number of NEBs was estimated to be around 3,500, approximately 40% of which were innervated by vagal sensory calbindin D28k-immunoreactive (IR) nerve endings and approximately 50% by spinal sensory calcitonin gene-related peptide (CGRP)-IR nerve terminals. The number of intrinsic pulmonary nitrergic neurons and the percentage of pulmonary NEBs revealing a nitrergic innervation were highly significantly lower in FHRs. In both FHRs and Wistar rats, a remarkable morphologic interaction was observed between the intrinsic nitrergic and the CGRP-IR sensory population contacting NEBs. Our findings suggest a possible link between the hypersensitivity to airway hypoxia observed in FHRs and a reduced intrinsic pulmonary nitrergic innervation, possibly via the interaction with pulmonary NEBs and their spinal sensory CGRP-IR innervation.