Intestinal serotonin acts as a paracrine substance to mediate vagal signal transmission evoked by luminal factors in the rat

The vagus nerve conveys primary afferent information produced by a meal to the brainstem. Serotonin (5-HT), which abounds in intestinal enterochromaffin cells, is released in response to various stimuli. We have recently demonstrated that 5-HT released from intestinal enterochromaffin cells activates 5-HT3 receptors on vagal afferent fibres to mediate luminal non-cholecystokinin-stimulated pancreatic secretion. The present study was designed to evaluate the responses of vagal sensory neurons to intraluminal osmotic stimulation and luminal infusion of maltose, glucose or 5-HT. We investigated the role of endogenous 5-HT in signal transmission evoked by luminal stimuli to activate vagal sensory neurons. The discharges of vagal primary afferent neurons innervating the intestine were recorded from rat nodose ganglia. Luminal factors such as intestinal osmotic stimuli and perfusion of carbohydrates elicited powerful vagal nodose responses. Electrical subdiaphragmatic vagal stimulation activated 364 single units; 40 of these responded to intestinal mucosal stimuli. Of these 40, 30 responded to intraduodenal perfusion of hyperosmolar NaCl (500 mosmol l(-1)), 27 responded to tap water (5 mosmol l(-1)) and 20 and 19 responded to maltose (300 mM) and glucose (277.5 mM), respectively. The 5-HT3/4 antagonist tropisetron (ICS 205-930) or 5-HT3 antagonist granisetron abolished luminal stimuli-evoked nodose neuronal responses. Intraluminal infusion of 10(-5) and 10(-4) M 5-HT elicited increases in vagal afferent discharge in 25 and 31 units, respectively, by activating the 5-HT3 receptors. Acute subdiaphragmatic vagotomy, intestinal mucosal application of the local anaesthetic lidocaine (lignocaine) or administration of 5-HT3 antagonist each abolished the luminal 5-HT-induced nodose neuronal responses. In contrast, distension-sensitive neurons did not respond to duodenal infusion of 5-HT. Pharmacological depletion of 5-HT stores using p-chlorophenylalanine (PCPA), a 5-HT-synthesis inhibitor, abolished luminal factor-stimulated nodose neuronal responses. In contrast, pretreatment with 5,7-dihydroxytryptamine (5,7-DHT), a specific 5-HT neurotoxin that destroys 5-HT-containing neurons without affecting 5-HT-containing mucosal cells, had no effect on these responses. These results suggested that the nodose neuronal responses to luminal osmolarity and to the digestion products of carbohydrates are dependent on the release of endogenous 5-HT from the mucosal enterochromaffin cells, which acts on the 5-HT3 receptors on vagal afferent fibres to stimulate vagal sensory neurons.

An experimental study on biomass air-steam gasification in a fluidized bed

The characteristics of biomass air-steam gasification in a fluidized bed are studied in this paper. A series of experiments have been performed to investigate the effects of reactor temperature, steam to biomass ratio (S/B), equivalence ratio (ER) and biomass particle size on gas composition, gas yield, steam decomposition, low heating value (LHV) and carbon conversion efficiency. Over the ranges of the experimental conditions used, the fuel gas yield varied between 1.43 and 2.57 Nm3/kg biomass and the LHV of the fuel gas was between 6741 and 9143 kJ/Nm3. The results showed that higher temperature contributed to more hydrogen production, but too high a temperature lowered gas heating value. The LHV of fuel gas decreased with ER. Compared with biomass air gasification, the introduction of steam improved gas quality. However, excessive steam would lower gasification temperature and so degrade fuel gas quality. It was also shown that a smaller particle was more favorable for higher gas LHV and yield.

Intestinal serotonin acts as paracrine substance to mediate pancreatic secretion stimulated by luminal factors

We recently demonstrated that luminal factors such as osmolality, disaccharides, and mechanical stimulation evoke pancreatic secretion by activating 5-hydroxytryptamine subtype 3 (serotonin-3, 5-HT3) receptors on mucosal vagal afferent fibers in the intestine. We hypothesized that 5-HT released by luminal stimuli acts as a paracrine substance, activating the mucosal vagal afferent fibers to stimulate pancreatic secretion. In the in vivo rat model, luminal perfusion of maltose or hypertonic NaCl increased 5-HT level threefold in intestinal effluent perfusates. Similar levels were observed after intraluminal 10(-5) M 5-HT perfusion. These treatments did not affect 5-HT blood levels. In a separate study, intraduodenal, but not intraileal, 5-HT application induced a dose-dependent increase in pancreatic protein secretion, which was not blocked by the CCK-A antagonist CR-1409. Acute vagotomy, methscopolamine, or perivagal or intestinal mucosal application of capsaicin abolished 5-HT-induced pancreatic secretion. In conscious rats, luminal 10(-5) M 5-HT administration produced a 90% increase in pancreatic protein output, which was markedly inhibited by the 5-HT3 antagonist ondansetron. In conclusion, luminal stimuli induce 5-HT release, which in turn activates 5-HT3 receptors on mucosal vagal afferent terminals. In this manner, 5-HT acts as a paracrine substance to stimulate pancreatic secretion via a vagal cholinergic pathway.

Temporal and spatial gene expression of major bone extracellular matrix molecules during embryonic mandibular osteogenesis in rats

It is not known how gene expression of bone extracellular matrix molecules is controlled temporally and spatially, or how it is related with morphological differentiation of osteoblasts during embryonic osteogenesis in vivo. The present study was designed to examine gene expressions of type I collagen, osteonectin, bone sialoprotein, osteopontin, and osteocalcin during mandibular osteogenesis using in situ hybridization. Wistar rat embryos 13-20 days post coitum were used. The condensation of mesenchymal cells was formed in 14-day rat embryonic mandibles and expressed genes of pro-alpha 1 (I) collagen, osteonectin, bone sialoprotein and osteopontin. Cuboidal osteoblasts surrounding the uncalcified bone matrix were seen as early as in 15-day embryonic mandibles, while flat osteoblasts lining the surface of the calcified bone were seen from 16-day embryonic mandibles. Cuboidal osteoblasts expressed pro-alpha 1(I) collagen, osteonectin and bone sialoprotein intensely but osteopontin very weakly. In contrast, flat osteoblasts expressed osteopontin very strongly. Osteocytes expressed the extracellular matrix molecules actively, in particular, osteopontin. The present study demonstrated the distinct gene expression pattern of type I collagen, osteonectin, bone sialoprotein, osteopontin and osteocalcin during embryonic mandibular osteogenesis in vivo.

Effects of cassia oil on serum and hepatic uric acid levels in oxonate-induced mice and xanthine dehydrogenase and xanthine oxidase activities in mouse liver

We investigated the hypouricemic effects of cassia oil extracted from Cinnamomum cassia using hyperuricemic mice induced by potassium oxonate, and its inhibitory actions against liver xanthine dehydrogenase (XDH) and xanthine oxidase (XOD) activities. Oral administration of cassia oil significantly reduced serum and hepatic urate levels in hyperuricemic mice in a time- and dose-dependent manner. At doses of 450 mg/kg of cassia oil or above, serum urate levels of the oxonate-pretreated mice were not different from the normal control mice. Cassia oil at 600 mg/kg was found to be as potent as allopurinol, which reduced hepatic urate levels to lower than normal. In normal mice, urate levels in liver, but not in serum, were altered with dose-dependent decrease after cassia oil treatment. Furthermore, the ratio, liver uric acid/serum uric acid, was determined after cassia oil administration with time- and dose-dependent decreases in hyperuricemic mice. The positive dose-dependent decrease ratio was also observed after cassia oil treatment in the normal animals. The decreased extent of ratio elicited by cassia oil in normal mice appeared to be greater than that in the hyperuricemic animal. In addition, cassia oil significantly exhibited marked reductions in liver XDH/XOD activities, with an apparent dose-dependence in the normal and hyperuricemic mice. The onset of inhibition in enzyme activities elicited by allopurinol was much higher than that elicited by cassia oil. These results suggested that hypouricemic effects of cassia oil could be explained, at least partly, by inhibiting liver in vivo activities of XDH/XOD.

Expression of major bone extracellular matrix proteins during embryonic osteogenesis in rat mandibles

It is not known how bone proteins appear in the matrix before and after calcification during embryonic osteogenesis. The present study was designed to investigate expressions of the five major bone extracellular matrix proteins--i.e. type I collagen, osteonectin, osteopontin, bone sialoprotein and osteocalcin--during osteogenesis in rat embryonic mandibles immunohistochemically, and their involvement in calcification demonstrated by von Kossa staining. Wistar rat embryos 14 to 18 days post coitum were used. Osteogenesis was not seen in 14-day rat embryonic mandibles. Type I collagen was localized in the uncalcifed bone matrix in 15-day mandibles, where no other bone proteins showed immunoreactivity. Osteonectin, osteopontin, bone sialoprotein and osteocalcin appeared almost simultaneously in the calcified bone matrix of 16-day mandibles and accumulated continuously in 18-day mandibles. The present study suggested that type I collagen constitutes the basic framework of the bone matrix upon which the noncollagenous proteins are oriented to lead to calcification, whereas the noncollagenous proteins are deposited simultaneously by osteoblasts and are involved in calcification cooperatively.

Flexible, transferable and conformal egg albumen based resistive switching memory devices

Egg albumen based RRAM devices transferred onto nonconventional substrates demonstrate flexible and conformal applications.

Immunohistochemical localization of type I collagen, fibronectin and tenascin C during embryonic osteogenesis in the dentary of mandibles and tibias in rats

Type I collagen, fibronectin and tenascin C play an important role in regulating early osteoblast differentiation, but the temporal and spatial relationship of their localization during embryonic osteogenesis in vivo is notknown. The present study was designed to localize these three molecules in the dentary of mandibles and tibias in rat embryos using immunohistochemistry. Serial paraffin sections were cut and adjacent sections were processed for von Kossa staining or immunohistochemistry for type I collagen, fibronectin and tenascin C. In the dentary, tenascin C was localized within and around the mesenchymal cell condensation in embryos at 14 days in utero. The bone matrix at 15 days showed immunoreactivity for both type I collagen and fibronectin. The immunoreactivity of type I collagen was persistent, whereas that of fibronectin decreased with age of embryos. In tibias, tenascin C was localized in the perichondral mesenchymal tissue at 17 days. Immunoreactivity for type I collagen was persistent in the bone matrix, whereas the tibial bone showed little immunoreactivity for fibronectin at any embryonic age examined. The present study demonstrated characteristic localization of type I collagen, fibronectin and tenascin C during embryonic osteogenesis in the dentary of mandibles and tibias.

Distinctive expression of extracellular matrix molecules at mRNA and protein levels during formation of cellular and acellular cementum in the rat

Little is known about differential expression of extracellular matrices secreted by cementoblasts between cellular and acellular cementum. We hypothesize that cementoblasts lining acellular cementum express extracellular matrix genes differently from those lining cellular cementum, thereby forming two distinct types of extracellular matrices. To test this hypothesis, we investigated spatial and temporal gene expression of selected extracellular matrix molecules, that is type I collagen, bone sialoprotein, osteocalcin and osteopontin, during formation of both cellular and acellular cementum using in situ hybridization. In addition, their extracellularly deposited and accumulated proteins were examined immunohistochemically. The mRNA transcripts of pro-alpha1 (I) collagen were primarily localized in cementoblasts of cellular cementum and cementocytes, while those of bone sialoprotein were predominantly seen in cementoblasts lining acellular cementum. In contrast, osteocalcin was expressed by both types of cementoblasts and cementocytes and so was osteopontin but only transiently. Our immunohistochemical examination revealed that translated proteins were localized extracellularly where the genes had been expressed intracellularly. The present study demonstrated the distinctive expression of genes and proteins of the extracellular matrix molecules between cellular and acellular cementum.

Expression of NKCC2 in the rat gastrointestinal tract

NKCC2, an isoform of Na+-K+-2Cl(-) cotransporter, is principally present in the kidney and plays a critical role in salt reabsorption. Expression of NKCC2 has been found in the apical membrane of intestinal epithelial cells in a number of marine fish, however, details for expression in the mammalian gastrointestinal tract are lacking. RT-PCR, Western blotting and immunohistochemistry were used to study the expression and localization of NKCC2 in the rat gastrointestinal tract. We found that mRNA transcripts, protein and immunoreactivity (IR) for NKCC2 were expressed in the stomach, small and large intestine of adult rats. NKCC2 IR was localized to the base of the gastric glands, intestinal epithelia, myenteric and submucosal plexuses. NKCC2 IR was expressed strongly in the apical membranes and weakly in the basolateral membranes of intestinal epithelial cells. In the enteric nervous system, NKCC2 IR was widely distributed and localized to enteric neurons with cholinergic, calretinin and nitrergic neuronal immunochemical codes in the myenteric plexus. It was localized to non-cholinergic secretomotor neurons in the submucosal plexus. In conclusion, this study for the first time clearly detected the expression of NKCC2 in the gastrointestinal tract of a mammalian species. Expression of NKCC2 in gastrointestinal epithelial cells suggested that this cation chloride cotransporter might be involved in gastrointestinal ion transport. Expression of NKCC2 in enteric neurons might contribute to the accumulation of Cl(-) and a more depolarized E(Cl)(-) in enteric neurons.

Metabotropic glutamate subtype 7 and 8 receptors oppositely modulate cardiac nociception in the rat nucleus tractus solitarius

Recent study from our laboratory has indicated that microinjection of glutamate into the nucleus tractus solitarius (NTS) facilitates the cardiac-somatic reflex induced by pericardial capsaicin. Further, N-methyl-d-aspartate (NMDA) receptors and metabotropic glutamate receptors (mGluRs) mediate this function. However, the roles of the individual receptor subtypes or subunits in modulating cardiac nociception are unknown. Among the three groups of mGluRs, group III mGluRs are the primary mGluR subtype expressed in visceral afferent neurons in the NTS. The present study examined the roles of group III mGluRs and their subtype 7 and 8 receptors (mGluR7 and mGluR8) in modulating the cardiac-somatic reflex induced by pericardial capsaicin, which was monitored by recording electromyogram (EMG) activity from the spinotrapezius muscle in anesthetized rats. Intra-NTS microinjection of a group III mGluR agonist, l-(+)-2-Amino-4-phosphonobutyric acid (l-AP4, at 1, 10, and 20 nmol) or a selective mGluR7 agonist, N,N'-diphenylmethyl-1,2-ethanediamine dihydrochloride (AMN082, at 1, 2, and 4 nmol) both decreased the EMG response in a dose-dependent manner. This decrease was inhibited by the group III mGluR antagonist (RS)-α-Methylserine-O-phosphate (MSOP, at 20 nmol). In contrast, intra-NTS microinjection of a selective mGluR8 agonist, (S)-3, 4-dicarboxyphenylglycine (DCPG, at 6 and 8 nmol), significantly increased the EMG response above control levels. This effect was eliminated by intra-NTS MSOP and by vagal deafferentation. These data suggest that group III mGluRs and mGluR7 in the NTS display an inhibitory effect, while mGluR8 displays a facilitatory effect in modulating cardiac nociception, and this facilitatory effect is dependent on vagal afferents.

Neurochemical phenotype of vagal afferent neurons activated to express C-FOS in response to luminal stimulation in the rat

The vagus nerve conveys meal-induced primary afferent responses to the brainstem. Electrophysiological studies indicate that luminal stimuli such as osmolarity and the digestion products of carbohydrates elicit powerful vagal nodose neuronal responses by activating serotonin 3 (5-hydroxytryptamine-3, 5-HT3) receptors on intestinal mucosal afferent fibers. To characterize the neurochemical phenotype of neurotransmitters in vagal nodose neurons that are activated by luminal stimulation, we examined c-fos protein (c-Fos) expression in response to luminal stimulation in conscious rats. A double-labeling technique using antisera to glutamate (Glu), substance P (SP), calcitonin gene-related peptide (CGRP), and somatostatin (SS) was used to determine the neurochemical profile of c-Fos-positive neurons. c-Fos immunoreactivity was insignificant in vehicle-treated rats. Luminal perfusions of NaCl (500 mOsm), tap water (5 mOsm), maltose (300 mmol/l), and 5-HT (10(-5) mol/l) each elicited a significant increase in the number of cells expressing c-Fos. Chronic vagotomy eliminated an increase in nodose neuronal c-Fos expression, and the 5-HT3 receptor antagonist granisetron significantly reduced it. Glu-, SP-, and CGRP-containing neurons represented 28%, 53%, and 19%, respectively, of the total population of nodose neurons. Few neurons contained SS. Double-labeling studies revealed that of the c-Fos-positive neurons responsive to hypertonic NaCl, 52%, 41%, and 3% exhibited immunoreactivity for Glu, SP, and CGRP, respectively. Of those responsive to tap water, 47%, 50%, and 4% exhibited immunoreactivity for Glu-, SP- and CGRP, respectively. In addition, 44%, 38%, and 8% of 5-HT-stimulated and 30%, 32%, and 5% of maltose-stimulated c-Fos-positive neurons exhibited, respectively, Glu, SP, and CGRP immunoreactivity. The few neurons that contained SS did not express c-Fos.

CONCLUSIONS

Vagal primary afferent neurons that respond to 5-HT-dependent luminal stimuli, such as hyperosmolarity and maltose, contain mainly Glu and SP. These neurons appear to play an important role in the mediation of the vago-vagal reflex elicited by luminal stimuli.

Expression and activation of β-adrenoceptors in the colorectal mucosa of rat and human

BACKGROUND

The functions of the distal colon are regulated by local and extrinsic neural pathways. In previous studies, we have found that dopamine (DA) and norepinephrine (NE) could evoke colonic ion transport by activating β-adrenoceptors. The present study aims to investigate the segmental differences in expression and activation of β-adrenoceptors in the distal colon in physiological and pathophysiological conditions.

METHODS

Real-time PCR, immunofluorescence, and Western blotting were used to detect the expression of β-adrenoceptors in the rat and human distal colon. Short-circuit current measurements (Isc) were used to assess the role of β-adrenoceptors in ion transport.

KEY RESULTS

DA and NE caused greater suppression of baseline Isc in distal colon adjacent to the rectum than in segments further away from the anus. These responses were inhibited by selective antagonists of β₁- and β₂-adrenoceptors, but not β₃-adrenoceptor. The expression levels of β₁- and β₂-adrenoceptors in colonic mucosa were higher in colorectum than the regions away from the anus of rats and humans. In wrap-restraint stress (2 h), DA-, NE-induced ΔIsc and the expression of β-adrenoceptors in the colorectum were significantly reduced. However, when endogenous catecholamines were depleted by 6-hydroxydopamine (75 mg kg(-1), i.p., 3 days), DA-, NE-induced ΔIsc as well as the expression of β-adrenoceptors were significantly enhanced in the rat colorectum but not in more proximal regions of the distal colon.

CONCLUSIONS & INFERENCES

β₁- and β₂-adrenoceptors are predominantly expressed in the colorectal mucosa. Perturbation of endogenous catecholamine levels influences the expression and activation of β-adrenoceptors in the colorectal region.

Peroxide induced tin oxide coating of graphene oxide at room temperature and its application for lithium ion batteries

We describe a new, simple and low-temperature method for ultra-thin coating of graphene oxide (GO) by peroxostannate, tin oxide or a mixture of tin and tin oxide crystallites by different treatments. The technique is environmentally friendly and does not require complicated infrastructure, an autoclave or a microwave. The supported peroxostannate phase is partially converted after drying to crystalline tin oxide with average, 2.5 nm cassiterite crystals. Mild heat treatment yielded full coverage of the reduced graphene oxide by crystalline tin oxide. Extensive heat treatment in vacuum at >500 °C yielded a mixture of elemental tin and cassiterite tin oxide nanoparticles supported on reduced graphene oxide (rGO). The usefulness of the new approach was demonstrated by the preparation of two types of lithium ion anodes: tin oxide-rGO and a mixture of tin oxide and tin coated rGO composites (SnO(2)-Sn-rGO). The electrodes exhibited stable charge/discharge cyclability and high charging capacity due to the intimate contact between the conductive graphene and the very small tin oxide crystallites. The charging/discharging capacity of the anodes exceeded the theoretical capacity predicted based on tin lithiation. The tin oxide coated rGO exhibited higher charging capacity but somewhat lower stability upon extended charge/discharge cycling compared to SnO(2)-Sn-rGO.

Cooperative effects of adenoviral vector-mediated interleukin 12 gene therapy with radiotherapy in a preclinical model of metastatic prostate cancer

We investigated the potential benefits of combining adenoviral vector mediated in situ interleukin-12 (AdmIL-12) gene therapy with radiation therapy (XRT) to enhance therapeutic efficacy. In a metastatic mouse prostate cancer cell line, 178-2 BMA, AdmIL-12+XRT demonstrated enhanced therapeutic activities in vitro as determined by clonogenic survival, apoptosis, and mIL-12 levels. At the molecular level, increased expression of tumor necrosis factor-alpha mRNA was specific for the combined therapy. In a subcutaneous 178-2 BMA in vivo model, the combination of AdmIL-12+XRT produced statistically significant tumor growth suppression compared to control vector Adbetagal, Adbetagal XRT, or AdmIL-12 as monotherapy. In addition, significant prolongation of survival was demonstrated for the combination of AdmIL-12+XRT. The combination of AdmIL-12+XRT significantly suppressed both spontaneous and pre-established lung metastases, and led to a prolonged elevation of serum IL-12 and significantly increased natural killer (NK) activities. Importantly, in vivo depletion of NK cells resulted in significant attenuation of the antimetastatic activities of AdmIL-12 alone or AdmIL-12+XRT. These combined effects suggest that AdIL-12 gene therapy together with radiotherapy may achieve maximal tumor control (both local and systemic) in selected prostate cancer patients via radio-gene therapy induced local cytotoxicity and local and systemic antitumor immunity.

Using mixture models to detect differentially expressed genes

An important and common problem in microarray experiments is the detection of genes that are differentially expressed in a given number of classes. As this problem concerns the selection of significant genes from a large pool of candidate genes, it needs to be carried out within the framework of multiple hypothesis testing. In this paper, we focus on the use of mixture models to handle the multiplicity issue. With this approach, a measure of the local false discovery rate is provided for each gene, and it can be implemented so that the implied global false discovery rate is bounded as with the Benjamini-Hochberg methodology based on tail areas. The latter procedure is too conservative, unless it is modified according to the prior probability that a gene is not differentially expressed. An attractive feature of the mixture model approach is that it provides a framework for the estimation of this probability and its subsequent use in forming a decision rule. The rule can also be formed to take the false negative rate into account.

Simultaneous multi-slice accelerated diffusion-weighted imaging with higher spatial resolution for patients with liver metastases from neuroendocrine tumours

AIM

To evaluate the imaging characteristics of simultaneous multi-slice (SMS) accelerated diffusion-weighted imaging (DWI) with decreased section thickness, with and without motion correction, in comparison to conventional DWI (cDWI) for the detection of lesions in patients with neuroendocrine tumour (NET) liver metastases.

MATERIALS AND METHODS

Fifteen patients with NET liver metastases underwent cDWI (section thickness [SL]=4 mm) and SMS-DWI (SL=2 mm). Non-linear motion-corrected (Moco)-SMS-DWI was generated in addition to the original series. Qualitative imaging characteristics (five-point Likert scale), the number of high signal lesions, and the detectability and delineation of lesions were evaluated and compared using the Friedman and the Dunn-Bonferroni tests. The test-retest variability (TRV) of the cDWI and SMS-DWI techniques was investigated among 11 healthy volunteers who underwent cDWI (SL=4 mm) and SMS-DWI (SL=4 mm) twice. The Friedman and the Dunn-Bonferroni post-hoc tests were used to compare the mean apparent diffusion coefficient (ADC) and the TRV in different liver regions between the three series.

RESULTS

Moco-SMS-DWI demonstrated significantly superior overall image quality (p<0.001) with significantly fewer artefacts (p=0.003) than cDWI. The number of lesions detected by cDWI, SMS-DWI, and Moco-SMS-DWI were 348, 504, and 523, respectively. The detectability and delineation of the lesions and the ADC values were significantly higher on the SMS-DWI and Moco-SMS-DWI images than on the cDWI images (all p<0.001). Moco-SMS-DWI showed significantly higher TRV than cDWI in regions near the liver edge (p=0.018).

CONCLUSIONS

SMS-DWI achieves higher spatial resolution than cDWI within the same acquisition time, detects more lesions, and provides better lesion delineation. By applying motion correction, the TRV of DWI could be enhanced in regions near the liver edge.