Recent advances in heme-protein sensors

In recent years, an increasing number of proteins have been discovered which utilize heme cofactors to sense oxygen, carbon monoxide and nitric oxide. The identification and characterization of these proteins are revising our understanding of heme-mediated allostery first established in the early 1960s. Biochemical and structural studies are revealing new mechanisms for heme-driven conformational changes distinct from the classical hemoglobin model.     

Expression of functional purinergic receptors in pulmonary neuroepithelial bodies and their role in hypoxia chemotransmission

Adenine nucleotides act through specific cell surface receptors to invoke a variety of biological responses. Here we show that cells of neuroepithelial bodies (NEB), presumed O2 airway sensors in neonatal hamster lung, express functional P2X receptors (P2X-R). Positive immunostaining was detected in NEB cells using double-label immunohistochemistry with antibodies against P2X2 and P2X3 receptor subunits, which co-localized with serotonin (5-HT), a marker of NEB cells. For electrophysiological characterization of P2X2-R in NEB cells, fresh neonatal hamster lung slice preparation was used. Under whole-cell patch clamp, perfusion with ATP induced a concentration-dependent, non-desensitizing inward current (EC50=12 microM). Perfusion with alpha,beta-methylene ATP also induced a slow-desensitizing inward current (EC50=8.2 microM). Suramin (IC50 ca. 43 microM) and TNP-ATP (IC50 ca. 8 microM) blocked the currents evoked by both ATP and alpha,beta-methylene ATP. Using carbon fiber amperometry we observed that hypoxia and ATP induced 5-HT release from NEB cells and that this release was blocked by suramin. These data suggest that functional P2X2/3 heteromeric receptors are expressed in NEB cells. The possible function of these purinoreceptors in NEB cells could include modulation of hypoxia chemotransmission.     

Quantitation of pulmonary neuroepithelial bodies in pre- and postnatal rabbits

Summary The size, density and total number of neuroepithelial bodies (NEB) in the lungs of late fetal, neonatal, and mature rabbits were determined using fluorescence microscopy. In this study lungs from 27-, 29-, 30-, and 31-day fetuses; neonates of ages 2, 7, and 30 days; and 4- and 7(+)-month-old rabbits, were used. The total number of NEB in the entire lung of rabbits from each age group was estimated based on measurements of collapsed lung volume, average NEB diameter, and NEB density (number/mm²). Average NEB diameter increased between 27 and 29 days gestation, then remained constant at 42–44 m between 29 days gestation and two days post-partum. Thereafter the diameter was significantly reduced in the 7-day group (33.7 m) and further reduced in the 4-month group (20.3 m). NEB density was initially high in 27-day fetuses (3.87/mm²), decreased significantly by 30 days gestation, increased to a high level by 2 days post-partum, then fell steadily, reaching the lowest level in the adult (0.15/mm²). This steady decrease in density was paralleled by a large increase in lung volume. The estimated total number of NEB in the lung was constant in all age groups except for a significant drop at 30 and 31 days gestation. These data indicate that the total number of NEB is maintained into adulthood; however, the density and average diameter of NEB decreases rapidly after 2 days postpartum. A sharp decrease in both total number and density observed under fluorescence microscopy at 30 and 31 days gestation suggests a change in NEB cellular activity just prior to birth.     

Innervation of pulmonary neuroendocrine cells and neuroepithelial bodies in developing rabbit lung.

We investigated the development of innervation of the pulmonary neuroendocrine cell (PNEC) system composed of single cells and organoid cell clusters, neuroepithelial bodies (NEB) in rabbit fetal and neonatal lungs. To visualize the nerve fibers and their contacts with PNECs/NEBs, we used confocal microscopy and multilabel immunohistochemistry (IHC) with pan-neural marker, synaptic vesicle protein 2 (SV2), and serotonin (5-HT) as markers for PNECs/NEBs, and smooth muscle actin or cytokeratin to identify airway landmarks. The numbers and distribution of PNEC/NEB at different stages of lung development (E16, 18, 21, 26, and P2) and the density of innervation were quantified. First PNECs immunoreactive for 5-HT were identified in primitive airway epithelium at E18 as single cells or as small cell clusters with or without early nerve contacts. At E21 a significant increase in the number of PNECs with formation of early innervated NEB corpuscules was observed. The overall numbers of PNECs/NEBs and the density of mucosal, submucosal, and intercorpuscular innervation increased with progressing gestation and peaked postnatally (P2). At term, the majority of NEBs and single PNECs within airway mucosa possessed neural contacts. Such an extensive and complex innervation of the PNEC system indicates a multifunctional role in developing lung and during neonatal adaptation.     

Recent advances in fluorescence sensors based on DNA–MOF hybrids

In this review, the recent advances in the development of fluorescence sensors based on DNA and metal–organic framework hybrids have been reported for nucleic acid, metal ion and amino acid detection. The main detection mechanism depends on different adsorption capacities of MOFs towards different DNA structures (single‐stranded DNA, double‐stranded DNA), and consequently the fluorescence intensity of probe DNA is changed. These results might open up a way to study their potential application in material science and clinical diagnosis of some related diseases.     

Expression of CFTR and Cl(-) conductances in cells of pulmonary neuroepithelial bodies

The pulmonary neuroendocrine cell system comprises solitary neuroendocrine cells and clusters of innervated cells or neuroepithelial bodies (NEBs). NEBs figure prominently during the perinatal period when they are postulated to be involved in physiological adaptation to air breathing. Previous studies have documented hyperplasia of NEBs in cystic fibrosis (CF) lungs and increased neuropeptide (bombesin) content produced by these cells, possibly secondary to chronic hypoxia related to CF lung disease. However, little is known about the role of NEBs in the pathogenesis of CF lung disease. In the present study, using a panel of cystic fibrosis transmembrane conductance regulator (CFTR)-specific antibodies and confocal microscopy in combination with RT-PCR, we demonstrate expression of CFTR message and protein in NEB cells of rabbit neonatal lungs. NEB cells expressed CFTR along with neuroendocrine markers. Confocal microscopy established apical membrane localization of the CFTR protein in NEB cells. Cl(-) conductances corresponding to functional CFTR were demonstrated in NEB cells in a fresh lung slice preparation. Our findings suggest that NEBs, and related neuroendocrine mechanisms, likely play a role in the pathogenesis of CF lung disease, including the early stages before establishment of chronic infection and chronic lung disease.     

Effects of unilateral vagal stimulation on intrapulmonary neuroepithelial bodies

We studied the influence of unilateral vagal stimulation on intrapulmonary neuroepithelial bodies (NEB) in rabbits. The left vagus nerve was cut and electrically stimulated for 10 min. Animals were killed and the lungs studied with fluorescence and electron microscopy. Intensity of formaldehyde-induced fluorescence, which reflects the serotonin content in NEB, was higher on the stimulated side than on the nonstimulated side (118 +/- 7 vs. 100%, n = 8, P less than 0.001). The latter difference was found to correlate with the stimulus amplitude (r = 0.9, P less than 0.05). Ultrastructurally a decrease in the number of exocytotic dense-cored vesicle (DCV) profiles at the level of the NEB basal epithelial cell membrane was found on the stimulated side (0.32 +/- 0.10 vs. 0.45 +/- 0.16 DCV/micron of basal epithelial cell membrane, n = 8, P less than 0.05). Section of the left vagus nerve without electrical stimulation affected neither the fluorescence intensity nor the number of exocytotic DCV profiles. In animals with supranodosal or infranodosal chronic vagotomy the observed effects of unilateral vagal stimulation were no longer present. We conclude that 1) vagal stimulation increases the serotonin content of NEB; 2) it decreases the number of exocytotic DCV profiles; 3) this effect depends on the amplitude of the stimulus; 4) it is obtained through efferent vagal fibers; 5) these results are the opposite of the effects seen after exposing normal NEB to acute hypoxia; and 6) these physiological experiments corroborate a vagal innervation of NEB, which may play an important role in modulating the sensitivity and reaction of NEB to various stimuli.     

Recent advances of surface acoustic wave-based sensors for noninvasive cell analysis

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神经肽Y参与痛觉调制的研究进展

神经肽Y（NPY）是中枢神经系统内含量最多的神经肽之一,它参与机体多种生理活动。近年来,对不同痛模型中NPY作用的研究表明,NPY可能通过激活脊髓和脊髓上水平的Y1受体或拮抗背根节的Y2受体发挥镇痛作用,此类研究将为NPY及其受体激动剂在镇痛中的应用提供重要的理论基础。本文就NPY及其Y1、Y2受体在痛觉调制中的作用作一简要综述。     

Morphology of the apudocytes and neuroepithelial bodies in the lungs of rats

Endocrine cells (apudocytes) and neuroepithelial bodies (NEBs) were revealed in the lungs of rats of different ages by Grimelius' argyrophilic method. Solitary apudocytes were found among the bronchial epitheliocytes, they had the oval, columnar or triangular shape. NEBs comprise groups of argyrophilic cells, in some cases the penetration of neural fibers into the bodies and their branching in the terminals are observed. Apudocytes and NEBs in 1-, 7-, and 15-day-old rats are more numerous in the epithelium of small than big bronchi. In 21- and 30-day-old and in adult animals apudocytes and NEBs are very scarce. The elements under study are likely to take part in the early postnatal development of the rat lungs.     

Hypoxic initiation of pulmonary hypertension is mediated by serotonin secretion from neuroepithelial bodies in chemodenervated dogs

The purpose of this study was to investigate the stimulatory effect of hypoxia on the secretion of serotonin by neuroepithelial bodies (NEB) as well as to determine the relation between its level and changes in pulmonary arterial pressure (PAP) and also to determinate the effect of serotonin antagonists (pizotifen and methysergide) on the responses of pulmonary and systemic arterial pressures. The experiments were carried out in peripheral chemoreceptor-denervated dogs anesthetized with Na penthabarbital (30 mg/kg i.v.). On the breathing of normoxic and hypoxic (7% O2-93% N2) gas mixtures and on the injection of KCN (80 microg/kg i.v.), PAP, systemic arterial blood pressure (BP), tidal volume (VT), respiratory frequency (f/min), ventilation minute volume (VE) were determined. Also PAP and BP were recorded before and after the injection of pizotifen (0.5 mg/kg i.v.) and methysergide (1 mg/kg i.v.) during normoxic or hypoxic gas mixture breathing. At the end of each experimantal phase, serotonin level, PaO2, PaCO2 and pHa values in blood samples obtained from left ventricle and femoral artery were determined. On the breathing of the hypoxic gas mixture of the chemodenervated dogs, VT, VE and BP significantly decreased (P < 0.001, P < 0.001, P < 0.01). The mean value of PAP and serotonin levels (ventricular and femoral) were found significantly increased when compared with the corresponding normoxic values (P < 0.001, P < 0.05). On the other hand, injection of KCN produced no significant changes in PAP, serotonin levels, BP and respiratory parameters. After the injection of pizotifen, PAP was significantly increased in hypoxia (P < 0.01). After the injection of methysergide, the response of PAP was completely abolished during the breathing of hypoxic gas mixture. The finding of the abolition of response of PAP to hypoxia after the injection of methysergide indicates that serotonin release from NEB may be responsible for the elevation of PAP in hypoxic hypoxia.     

Recent advances in the role and biosynthesis of ascorbic acid in plants

The past few years have provided many advances in the role and biosynthesis of L -ascorbic acid (AsA) in plants. There is an increasing body of evidence confirming that AsA plays an important role in the detoxification of reactive oxygen species. The role of AsA in photoprotection has been confirmed in vivo with the use of Arabidopsis mutants. A player in the defence against reactive oxygen species, AsA peroxidase, has been extensively studied at the molecular level, and regulation of this key enzymatic activity appears to occur at several levels. As a cofactor in the hydroxylation of prolyl and lysl-residues by peptidyl-prolyl and -lysyl hydroxylases, AsA plays a part in cell wall synthesis, defence, and possibly cell division. The maintenance of reduced levels of AsA appears to be highly regulated, involving the interplay of both monodehydroascorbate and dehydroascorbate reductases and possibly auxin. A major breakthrough in plant AsA biosynthesis has been made recently, and strong biochemical and genetic evidence suggest that GDP-mannose and L -galactose are key substrates. In addition, evidence for an alternative AsA biosynthetic pathway(s) exists and awaits additional scrutiny. Finally, newly described Arabidopsis mutants deficient in AsA will further increase our understanding of AsA biosynthesis     

植物内生菌研究进展及其存在的问题

植物内生菌是一个多样性十分丰富的微生物类群 ,分布于没有外在感染症状的健康植物组织内 ,并与宿主植物协同进化 ,其存在和作用长期以来一直为人们所忽视。随着研究领域的不断拓宽和研究方法的不断深入 ,植物内生菌的生态和生理作用及其作为潜在的生防资源和外源基因载体 ,在农业和医药领域中的巨大应用潜力 ,已逐渐成为国内外研究的热点。本文综述了近 10年来国内外植物内生菌研究的概况和最新进展 ,并对该研究领域中存在的若干问题进行了探讨。     

植物内生菌的研究进展

植物内生菌是存在于植物内部与植物密不可分的一类微生物,包括内生真菌和内生细菌两大类。随着研究的不断深入,发现内生菌不仅产生多种有益的生物学作用,如防病、促生、固氮等,还能对寄主植物的生长发育产生不利影响。近年来,植物内生菌已成为我国微生物学领域研究的热点问题之一。本文综述了植物内生真菌和内生细菌的研究概况,以期更好地研究和了解植物内生菌。     

新型产甲烷古菌研究进展

产甲烷古菌是一类能利用简单化合物产生甲烷气体的厌氧菌。近年来,随着测序技术的不断发展,科学家结合宏基因组学和其他技术先后发现了众多之前未被报道的新型产甲烷古菌。基因组分析等研究发现这几类新型产甲烷古菌具有独特的甲烷代谢通路以及广泛的生态分布,科学家推测它们在全球生态调节以及碳循环中可能起到了不可忽视的作用。然而,这些新型产甲烷古菌大部分尚未通过传统培养方法获得纯培养菌株,其确切的生理代谢机制和生态功能还有待深入研究。为了更加系统地了解这些新型产甲烷古菌,本文从它们的分类、系统发育地位、代谢机制、生态分布以及分离培养等方面进行了综述,并对新型产甲烷古菌未来的研究方向进行了展望。