Morphology and distribution of sensilla on antennae and mouthparts of the adult bruchid beetles, Bruchidius coreanus (Coleoptera: Bruchidae)

Bruchidius coreanus is a serious pest on Gleditsia sinensis Lam during seed storage, causing significant losses to their yield in southwest China. To gain insight into their behavioral mechanisms, the external morphology, ultrastructure, and distribution of sensilla on antennae, maxillary palps, and labial palps of both male and female B. coreanus were observed using a scanning electron microscope. The results revealed that both male and female adults had serrated antennae comprising a scape, a pedicel, and nine flagellomeres (F1-F9). There were eight types and seven subtypes of antenna sensilla observed in both sexes, including Böhm sensilla (BS), two subtypes of sensilla chaetica (SC1 and SC2), two subtypes of sensilla trichodea (ST1 and ST2), three subtypes of sensilla basiconica (SB1, SB2, and SB3), sensilla auricillica (SA), sensilla styloconicum (SS), capitate pegs (CP), and sensilla cavity (SCa). The average length of BS and ST (ST1 and ST2) showed significant differences between males and females. Furthermore, the number of SC (SC1 and SC2), ST1, and SCa differed significantly between the sexes. Four types of sensilla were found on the maxillary palps and labial palps, with the length of ST on these palps significantly differing between males and females. Additionally, SS on male labial palps was significantly longer than in females. The number of SC significantly differed between the male and female maxillary palps and labial palps, while ST and SS showed significant differences in the maxillary palps. These findings will contribute to further electrophysiological recording and behavioral research. RESEARCH HIGHLIGHTS: The external morphology and distribution of various sensilla on the antennae, maxillary palps, and labial palps of Bruchidius coreanus were described. Eight types and seven subtypes of antenna sensilla were observed on the antennae, while four types of sensilla were observed on the maxillary palps and labial palps. The capitate pegs were found exclusively on the antennae of female B. coreanus.

Cold tolerance strategy and cryoprotectants of Megabruchidius dorsalis in different temperature and time stresses

The honey locusts (genus Gleditsia) are a genus of high-value trees in Asia. Seed beetle, Megabruchidius dorsalis (Fåhraeus) (Col.: Chrysomelidae: Bruchinae), is a Gleditsia oligophagous pest that causes severe yield reduction. To understand the cold tolerance of M. dorsalis adults, this study investigated its cold tolerance strategy and the influence of low temperatures on its physiology and biochemistry. The low-temperature treatments were divided into three groups: long-term temperature acclimation (Group 1; 15°C, or 20°C, or 25°C, or 28°C [control check, CK] for 10 days), short-term low-temperature exposure (Group 2; 0°C or 4°C for 2 h), and long-term low-temperature induction (Group 3; 0°C or 4°C for 1, 3, or 5 d). The supercooling point (SCP; temperature at which spontaneous nucleation and ice lattice growth begin), freezing point (FP; temperature at which insect fluids freeze), low lethal temperature (LLT; temperature at which all individuals are killed), water, lipid, glycerol, and total sugars contents were measured under different temperature stresses. The results showed that M. dorsalis adults were a freeze-avoidant species. The SCP and LLT at 28°C were -10.62°C and -19.48°C, respectively. The SCP and FP of long-term temperature acclimation (15°C, or 20°C, or 25°C) were significantly lower than that of the control group (28°C). The water content of the long-term low temperature induction (0°C) group was significantly lower than that of the control group. The lipid and glycerol content in the acclimated group at 20°C and 25°C were significantly higher than in the control group. M. dorsalis adults may maintain their biofluids in a supercooled state via cryoprotectant accumulation and cryoprotective dehydration to prevent ice nucleation. This study provides a theoretical basis for future research on overwintering and potential distribution and related prediction of M. dorsalis adults.

[Progress in the Role of Mechanical Stimulus in Cardiac Development]

Mechanical stimulus is critical to cardiovascular development during embryogenesis period.The mechanoreceptors of endocardial cells and cardiac myocytes may sense mechanical signals and initiate signal transduction that induce gene expression at a cellular level,and then translate molecular-level events into tissue-level deformations,thus guiding embryo development.This review summarizes the regulatory roles of mechanical signals in the early cardiac development including the formation of heart tube,looping,valve and septal morphogenesis,ventricular development and maturation.Further,we discuss the potential mechanical transduction mechanisms of platelet endothelial cell adhesion molecule 1-vascular endothelial-cadherin-vascular endothelial growth factor receptor 2 complex,primary cilia,ion channels,and other mechanical sensors that affect some cardiac malformations.

Effect of Photoperiod on Longevity, Food Consumption, and Reproduction of Holotrichia oblita (Coleoptera: Scarabaeidae)

Holotrichia oblita (Faldermann) (Coleoptera: Scarabaeidae) is a major soil insect pest that damages forest trees, crops, and lawns. Adults of H. oblita fly, forage, and mate at night but remain underground during the day. We studied the effect of photoperiod on H. oblita reproduction. H. oblita females laid more eggs at 8:16 (L:D) h and 0:24 (L:D) h than other photoperiods. As the scotophase increased, the preoviposition period decreased and the oviposition period increased. Female longevity exceeded that of males at all photoperiods, and both males and females at 0:24 (L:D) h had the shortest longevity. The number of eggs laid per female increased with increasing food consumption. Females at 8:16 (L:D) h had the greatest food consumption and laid the most eggs, while females at 24:0 (L:D) h had the lowest food consumption and laid few eggs. The food intake of adults increased gradually and decreased slowly after reaching a peak. Females began to lay eggs when their food consumption reached a maximum. These results indicate that a scotophase is necessary for the reproduction of H. oblita. A long scotophase promotes greater oviposition. The effect of photoperiod on reproduction is affected by food intake.

Generation and characterization of cardiac valve endothelial-like cells from human pluripotent stem cells

The cardiac valvular endothelial cells (VECs) are an ideal cell source that could be used for making the valve organoids. However, few studies have been focused on the derivation of this important cell type. Here we describe a two-step chemically defined xeno-free method for generating VEC-like cells from human pluripotent stem cells (hPSCs). HPSCs were specified to KDR⁺/ISL1⁺ multipotent cardiac progenitors (CPCs), followed by differentiation into valve endothelial-like cells (VELs) via an intermediate endocardial cushion cell (ECC) type. Mechanistically, administration of TGFb1 and BMP4 may specify VEC fate by activating the NOTCH/WNT signaling pathways and previously unidentified targets such as ATF3 and KLF family of transcription factors. When seeded onto the surface of the de-cellularized porcine aortic valve (DCV) matrix scaffolds, hPSC-derived VELs exhibit superior proliferative and clonogenic potential than the primary VECs and human aortic endothelial cells (HAEC). Our results show that hPSC-derived valvular cells could be efficiently generated from hPSCs, which might be used as seed cells for construction of valve organoids or next generation tissue engineered heart valves.

Cheng et al. provide a detailed characterization of the differentiation of human pluripotent stem cells to valve endothelial cells and their function. Their results show that the valve endothelial-like cells express key markers for valve endothelial cells, exhibiting proliferative and clonogenic potential.

Clinical efficacy of tocilizumab treatment in severe and critical COVID-19 patients

BACKGROUND

The main pathophysiological basis of coronavirus disease 2019 (COVID-19) causing respiratory failure is a cytokine storm and interleukin-6 (IL-6) is an important component of the COVID-19 cytokine storm. As a specific antagonist of IL-6, tocilizumab may block the cytokine storm of COVID-19. The Diagnosis and Treatment Guidelines of New Coronavirus Pneumonia (7^th Edition) includes tocilizumab as a recommended drug for immunotherapy in severe and critical COVID-19 patients. However, the specific clinical efficacy of tocilizumab in the treatment of COVID-19 patients is worth studying.

AIM

To determine the clinical efficacy of tocilizumab in inhibiting the cytokine storm in COVID-19.

METHODS

In total, 19 severe and critical COVID-19 patients were enrolled in this study, and were treated with tocilizumab in Optical Valley Campus of Hubei Maternal and Child Health Care Hospital from February 20 to March 31, 2020. The imaging manifestations and clinical data before and after treatment were analyzed retrospectively, including routine peripheral venous blood tests, routine blood biochemical tests, coagulation test, C-reactive protein (CRP), IL-6, and arterial blood gas analysis.

RESULTS

Of the 19 patients in this group, 13 (68.4%) had significantly improved symptoms of COVID-19 (5 patients were discharged directly and 8 patients were transferred after improvement) following treatment. One case was invalid, 1 case was exacerbated, and 4 deaths (21.1%) were observed (all critical cases). The lymphocyte count, CRP, lactic acid, oxygenation index, fibrinogen (FIB) and IL-6 levels were significantly different in the improved group.

CONCLUSION

Tocilizumab treatment is effective against IL-6 in COVID-19 patients, but it does not completely inhibit the inflammation and cytokine storm in all patients with COVID-19.In the clinical treatment of COVID-19 patients, attention should be paid to the timing of drug administration and other adjuvant treatments.

[Composition of phenolic allelochemicals in Eupatorium adenophorum root zone soils and its effects on soil-borne pathogens]

The allelochemicals released by Eupatorium adenophorum roots is an important factor inducing the changes of the weed soil environment, which provides favorable conditions for the successful invasion of the weed. By using GC/MS technique, the components and their relative contents of phenolic allelochemicals in aphid-infested and non-infested E. adenophorum root zone soils were analyzed, with unplanted soil as the control. Less difference was observed in the components of phenolic allelochemicals among the test soils, but their relative contents differed significantly. The relative contents of benzoic acid and 4-hydroxybenzoic acid in aphid-infested E. adenophorum root zone soil were significantly higher than the control; whereas that of 4-hydroxylcinnamic acid was in reverse. In the test three soils, the proportions of benzoic acid, 4-hydroxybenzoic acid, and 4-hydroxylcinnamic acid were different. The bacteriostatic test with the three acids and their combinations based on their proportions in test soils showed that at lower concentrations (50-150 mg x L(-1)), the three acids had significant inhibitory effects on five kinds of soil-borne pathogens, but their combinations had different inhibitory effects on the five pathogens, with the effects being significantly higher for the combinations with the proportions in non-infested E. adenophorum root zone soil and the control.

[Priming with an HEV Th epitope can improve the humoral immunogenicity of its native protein]

A dominant H-2d restricted Th epitope P34 was found to be contained in recombinant particulate hepatitis E virus (HEV) vaccine HEV 239. In this paper, the cellular immune response induced in P34 immunized BALB/c mice were studied and the priming effect of P34 was characterized. Groups of BALB/c mice were subcutaneously (s. c.) immunized with P34, splenocytes were then stimulated with P34 and HEV 239 protein, cellular immune response was assayed by IFN-gamma-ELISPOT, flow cytometry and T cell proliferation experiments. Results showed that P34 immunized BALB/c splenocytes responsed to P34 and HEV 239 protein stimulation in IFN-gamma-ELISPOT, flow cytometry and T cell proliferation experiments. After depletion of the CD4+ T cells from the immunized splenocytes by magnetic separation, the response decreased to the background level while almost no influence was observed after CD8 + T cells depletion which showed that the cells responsible for IFN-gamma secretion were mainly CD4+ T cells. Then mice were primed with P34 and boosted with its vector protein, E2, the E2 specific antibody titer were assayed. Results showed that after P34 priming, some of the 10 microg, 20 microg E2 boosted mice could develop anti-E2 antibody 1 week later and all the mice had detectable antibody 3 weeks after boosting. In the control peptide P18 priming group, even after boosting with 20 microg E2, anti-E2 antibody couldn't be detected until the end of this experiment. The results showed that priming with P34 epitope could increase the immunogenicity of its vector protein, E2, in BALB/c mice.

Metal Phthalocyanine Nanoribbons and Nanowires

Nanoribbons and nanowires of different metal phthalocyanines (copper, nickel, iron, cobalt, and zinc), as well as copper hexadecafluorophthalocyanine (F(16)CuPc), have been grown by organic vapor-phase deposition. Their properties, as a function of substrate type, source-to-substrate distance, and substrate temperature, were studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and absorption measurements. The size and morphology of the nanostructures were found to be mainly determined by the substrate temperature. The crystal structure was dependent on the substrate temperature as well. At substrate temperatures below 200 degrees C, in addition to straight nanoribbons, twisted nanoribbons were found for all investigated materials except F(16)CuPc, which formed helical nanoribbons upon exposure to an electron beam. The formation of different nanostructures (nanoribbons, twisted nanoribbons, and helical nanoribbons) is discussed.

Efficient multiphoton-absorption-induced luminescence in single-crystalline ZnO at room temperature

At room temperature, multiphoton absorption- (MPA-) induced photoluminescence in ZnO strongly driven by a femtosecond (fs) near-infrared laser is studied. Two-photon absorption and three-photon absorption are proved to be responsible for the intense luminescence, when the wavelength of the fs excitation laser is above and below the half-bandgap of ZnO, respectively. Strong MPA absorption in ZnO is unambiguously evidenced by the interferometric autocorrelation measurements of the luminescence signal.

Surface atomic arrangement visualization via reference-atom-specific holography

We demonstrate the direct reconstruction of 3D atomic images from measured low-energy electron diffraction (LEED) intensity spectra. A multiple-incident angle and multiple-energy integral are first applied to the spectra to obtain a map of interatomic vectors. From this map, a nonbulk interatomic vector is chosen that points to a desired reference atom. A second integral transformation, using the chosen interatomic vector as a filter, is applied to the LEED spectra to produce images of individual atoms in the vicinity of the selected reference atom. This two-step method overcomes the problem of multiple, nonequivalent reference atoms and is applicable to elemental or compound materials.

Acinar cells of the pancreas are a target of interleukin-22

Interleukin-22 (IL-22) (also reported as IL-10-related T cell-derived inducible factor, IL-TIF) is a recently identified cytokine found to signal through a receptor comprising the class II cytokine receptor family members IL-10Rbeta/CRF2-4 and IL-22R. Previous work has established that IL-10Rbeta, also a component of the IL10R complex, exhibits a broad distribution of mRNA expression. Here, we observe that IL-22R exhibits a restricted expression pattern, with highest levels of mRNA expression in pancreas and detectable expression in multiple other tissues, particularly liver, small intestine, colon, and kidney. We find that isolated primary pancreatic acinar cells and the acinar cell line 266-6 respond to IL-22 with activation of Stat3 and changes in gene transcription. IL-22 mediates robust induction of mRNA for pancreatitis-associated protein (PAP1)/Reg2 and osteopontin (OPN). PAP1 is a secreted protein related to the Reg family of trophic factors and was initially characterized as a protein elevated in pancreatitis. In vivo injection of IL-22 resulted in rapid induction of PAP1 in pancreas, a response not observed in mice deficient in IL-10Rbeta. These results support the conclusion that IL-10Rbeta is a required common component of both the IL-10 and IL-22 receptors and suggest that IL-22 may play a role in the immune response in pancreas.

Development of Th1-type immune responses requires the type I cytokine receptor TCCR

On antigen challenge, T-helper cells differentiate into two functionally distinct subsets, Th1 and Th2, characterized by the different effector cytokines that they secrete. Th1 cells produce interleukin (IL)-2, interferon-gamma (IFN-gamma) and lymphotoxin-beta, which mediate pro-inflammatory functions critical for the development of cell-mediated immune responses, whereas Th2 cells secrete cytokines such as IL-4, IL-5 and IL-10 that enhance humoral immunity. This process of T-helper cell differentiation is tightly regulated by cytokines. Here we report a new member of the type I cytokine receptor family, designated T-cell cytokine receptor (TCCR). When challenged in vivo with protein antigen, TCCR-deficient mice had impaired Th1 response as measured by IFN-gamma production. TCCR-deficient mice also had increased susceptibility to infection with an intracellular pathogen, Listeria monocytogenes. In addition, levels of antigen-specific immunoglobulin-gamma2a, which are dependent on Th1 cells, were markedly reduced in these mice. Our results demonstrate the existence of a new cytokine receptor involved in regulating the adaptive immune response and critical to the generation of a Th1 response.

Interleukin (IL)-22, a novel human cytokine that signals through the interferon receptor-related proteins CRF2-4 and IL-22R

We report the identification of a novel human cytokine, distantly related to interleukin (IL)-10, which we term IL-22. IL-22 is produced by activated T cells. IL-22 is a ligand for CRF2-4, a member of the class II cytokine receptor family. No high affinity ligand has yet been reported for this receptor, although it has been reported to serve as a second component in IL-10 signaling. A new member of the interferon receptor family, which we term IL-22R, functions as a second component together with CRF2-4 to enable IL-22 signaling. IL-22 does not bind the IL-10R. Cell lines were identified that respond to IL-22 by activation of STATs 1, 3, and 5, but were unresponsive to IL-10. In contrast to IL-10, IL-22 does not inhibit the production of proinflammatory cytokines by monocytes in response to LPS nor does it impact IL-10 function on monocytes, but it has modest inhibitory effects on IL-4 production from Th2 T cells.

Observation of "Ghost" islands and surfactant effect of surface gallium atoms during GaN growth by molecular beam epitaxy

We observe "ghost" islands formed on terraces during homoepitaxial nucleation of GaN. We attribute the ghost islands to intermediate nucleation states, which can be driven into "normal" islands by scanning tunneling microscopy. The formation of ghost islands is related to excess Ga atoms on the surface. The excess Ga also affect island number density: by increasing Ga coverage, the island density first decreases, reaching a minimum at about 1 monolayer (ML) Ga and then increases rapidly for coverages above 1 ML. This nonmonotonic behavior points to a surfactant effect of the Ga atoms.

FGF-19, a novel fibroblast growth factor with unique specificity for FGFR4

We have identified a novel fibroblast growth factor, FGF-19, the most distant member of the FGF family described to date. FGF-19 is a high affinity, heparin dependent ligand for FGFR4 and is the first member of the FGF family to show exclusive binding to FGFR4. Human FGF-19 maps to chromosome 11 q13.1, a region associated with an osteoporosis-pseudoglioma syndrome of skeletal and retinal defects. FGF-19 message is expressed in several tissues including fetal cartilage, skin, and retina, as well as adult gall bladder and is overexpressed in a colon adenocarcinoma cell line.

Toll-like receptor-2 mediates lipopolysaccharide-induced cellular signalling

Vertebrates and invertebrates initiate a series of defence mechanisms following infection by Gram-negative bacteria by sensing the presence of lipopolysaccharide (LPS), a major component of the cell wall of the invading pathogen. In humans, monocytes and macrophages respond to LPS by inducing the expression of cytokines, cell-adhesion proteins, and enzymes involved in the production of small proinflammatory mediators. Under pathophysiological conditions, LPS exposure can lead to an often fatal syndrome known as septic shock. Sensitive responses of myeloid cells to LPS require a plasma protein called LPS-binding protein and the glycosylphosphatidylinositol-anchored membrane protein CD14. However, the mechanism by which the LPS signal is transduced across the plasma membrane remains unknown. Here we show that Toll-like receptor 2 (TLR2) is a signalling receptor that is activated by LPS in a response that depends on LPS-binding protein and is enhanced by CD14. A region in the intracellular domain of TLR2 with homology to a portion of the interleukin (IL)-1 receptor that is implicated in the activation of the IL-1-receptor-associated kinase is required for this response. Our results indicate that TLR2 is a direct mediator of signalling by LPS.

Direct demonstration of MuSK involvement in acetylcholine receptor clustering through identification of agonist ScFv

MuSK is a tyrosine kinase localized to the postsynaptic surface of the neuromuscular junction. We have searched for modulators of MuSK function using a library of human single chain variable region antibodies (scFv) that can be displayed on M13 phage or expressed as soluble protein. A panel of 21 independent MuSK-specific scFv, identified in a screen for binding to MuSK-Fc immunoadhesin, were examined for ability to induce proliferation in a factor dependent cell line (Ba/F3) through a chimeric receptor, MuSK-Mpl. Four of the scFv induced a proliferative response, suggesting an ability to induce dimerization of MuSK. These scFv were also able to induce tyrosine phosphorylation of full-length MuSK and retained this ability when re-engineered to be expressed as authentic (and dimeric) human IgG molecules. Addition of agonist scFv to a cultured myotube cell line induced AChR clustering and tyrosine phosphorylation. These results provide direct evidence that MuSK activation is capable of triggering a key event in neuromuscular junction formation and further demonstrate that large libraries of phage-displayed scFv provide a robust method for generating highly specific agonist agents.

Cloning and characterization of a human leptin receptor using a biologically active leptin immunoadhesin

Leptin, the product of the ob gene, is a hormone secreted by fat cells which is primarily involved in the regulation of body weight. We have generated a leptin immunoadhesin (leptin-IgG) which was more potent than leptin alone at reducing body weight and food intake when injected into ob/ob mice. This molecule was used to identify high affinity binding sites on human embryonic 293 kidney cells and subsequently to isolate a cDNA encoding the leptin receptor from this cell line by expression cloning. This receptor corresponds to the short form of the recently isolated leptin receptor. Analysis of the expression pattern of the two forms of receptor by Northern blot, in situ hybridization and quantitative PCR showed that the receptor is expressed in most tissues but that the long form is prevalent in the hypothalamus.

Enhanced secretion of glycocholic acid in a specially adapted cell line is associated with overexpression of apparently novel ATP-binding cassette proteins

Secretion of anionic endo- and xenobiotics is essential for the survival of animal and plant cells; however, the underlying molecular mechanisms remain uncertain. To better understand one such model system--i.e., secretion of bile acids by the liver--we utilized a strategy analogous to that employed to identify the multidrug resistance (mdr) genes. We synthesized the methyl ester of glycocholic acid (GCE), which readily enters cells, where it is hydrolyzed to yield glycocholic acid, a naturally occurring bile acid. The rat hepatoma-derived HTC cell line gradually acquired resistance to GCE concentrations 20-fold higher than those which inhibited growth of naive cells, yet intracellular accumulation of radiolabel in resistant cells exposed to [14C]GCE averaged approximately 25% of that in nonresistant cells. As compared with nonresistant cells, resistant cells also exhibited (i) cross-resistance to colchicine, a known mdr substrate, but not to other noxious substances transported by hepatocytes; (ii) increased abundance on Northern blot of mRNA species up to 7-10 kb recognized by a probe for highly conserved nucleotide-binding domain (NBD) sequences of ATP-binding cassette (ABC) proteins; (iii) increased abundance, as measured by RNase protection assay, of mRNA fragments homologous to a NBD cRNA probe; and (iv) dramatic overexpression, as measured by Western blotting and immunofluorescence, of a group of 150- to 200-kDa plasma membrane proteins recognized by a monoclonal antibody against a region flanking the highly conserved NBD of mdr/P-glycoproteins. Finally, Xenopus laevis oocytes injected with mRNA from resistant cells and incubated with [14C]GCE secreted radiolabel more rapidly than did control oocytes. Enhanced secretion of glycocholic acid in this cell line is associated with overexpression of ABC/mdr-related proteins, some of which are apparently novel and are likely to include a bile acid transport protein.

Genomic structure, chromosomal localization, and conserved alternative splice forms of thrombopoietin

Thrombopoietin (TPO), the ligand for c-mpl, is a novel cytokine comprising an amino terminal domain with homology to erythropoietin and a glycosylated carboxyl terminal domain that does not bear overall homology to other known proteins. We report the cloning of cDNAs encoding the porcine and murine TPO and the characterization of the human TPO gene. The cDNA for an additional splice form (TPO-2) with a four-amino-acid deletion within the erythropoietin-like domain has been isolated and is conserved between humans, pigs, and mice. Species comparison of TPO shows that the amino terminal erythropoietin-like domain is highly conserved, while the carboxyl terminal domain is less conserved. Recombinant murine TPO and human TPO are each able to activate both the murine and human c-mpl receptors, indicating an absence of strict species specificity. Human TPO is encoded by a single gene consisting of six exons and located on chromosome 3q27-28.

Vasopressin increases cytosolic sodium concentration in hepatocytes and activates calcium influx through cation-selective channels

A variety of hormonal agonists activate transmembrane Na+ and Ca2+ flux in hepatocytes, but the responsible mechanisms are poorly understood. We employed microfluorimetric and patch clamp recording techniques in hepatocytes to determine the effect of the hormone vasopressin on cytosolic Na+ concentration ([Na+]i) and to identify the transmembrane Na+ transport pathways activated by this agonist. Under basal conditions, [Na+]i, measured using the Na(+)-sensitive fluorophore sodium-binding benzofuran isophthalate, averaged 12.1 +/- 1.6 mM. Exposure to vasopressin rapidly increased [Na+]i by 8.3 +/- 0.9 mM. This increase was attributable to activation of Na+ influx. It occurred in the absence of solutes co-transported with Na+ and was not associated with activation of Na+/H+ antiport. In cell-attached membrane patches, vasopressin activated ion channels that carried inward positive current at the resting membrane potential. Further characterization in excised membrane patches revealed two classes of ion channels, with conductances of 16.0 +/- 2.8 and 30.9 +/- 3.1 picosiemens, respectively. Single channel currents reversed near 0 mV, and ion substitution studies demonstrated that each channel type was permeable to Na+, Ca2+, and K+ but not Cl-. These observations in hepatocytes indicate that vasopressin increases [Na+]i and activates cation-selective channels, which likely accounts for vasopressin-activated Na+ and Ca2+ influx.

Transmembrane electrical potential difference regulates Na+/HCO3- cotransport and intracellular pH in hepatocytes

We have examined the hypothesis that a regulatory interplay between pH-regulated plasma membrane K+ conductance (gK+) and electrogenic Na+/HCO3- cotransport contributes importantly to regulation of intracellular pH (pHi) in hepatocytes. In individual cells, membrane depolarization produced by transient exposure to 50 mM K+ caused a reversible increase in pHi in the presence, but not absence, of HCO3-, consistent with voltage-dependent HCO3- influx. In the absence of HCO3-, intracellular alkalinization and acidification produced by NH4Cl exposure and withdrawal produced membrane hyperpolarization and depolarization, respectively, as expected for pHi-induced changes in gK+. By contrast, in the presence of HCO3-, NH4Cl exposure and withdrawal produced a decrease in apparent buffering capacity and changes in membrane potential difference consistent with compensatory regulation of electrogenic Na+/HCO3- cotransport. Moreover, the rate of pHi and potential difference recovery was several-fold greater in the presence as compared with the absence of HCO3-. Finally, continuous exposure to 10% CO2 in the presence of HCO3- produced intracellular acidification, and the rate of pHi recovery from intracellular acidosis was inhibited by Ba2+, which blocks pHi-induced changes in gK+, and by 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid, which inhibits Na+/HCO3- cotransport. These findings suggest that in hepatocytes, changes in transmembrane electrical potential difference, mediated by pH-sensitive gK+, play a central role in regulation of pHi through effects on electrogenic Na+/HCO3- cotransport.

Plasma membrane H(+)-HCO3- transport in rat hepatocytes: a principal role for Na(+)-coupled HCO3- transport

Na(+)-coupled HCO3- transport has been demonstrated in the basolateral membrane of hepatocytes, but there is uncertainty regarding its stoichiometry or capacity compared with other mechanisms of H(+)-HCO3- transport. After preincubation in medium free of Na+, either in the presence or absence of HCO3(-)-CO2, rat hepatocytes in primary culture were reexposed to Na+ or HCO3(-)-CO2 alone or in combination. Transporter electrogenicity was assessed by measuring membrane potential difference (PD), and the relative capacities of Na(+)-coupled HCO3- transport, Cl(-)-HCO3- exchange, and Na(+)-H+ exchange were assessed by measuring the magnitude and rate of change of intracellular pH (pHi) using BCECF. In the absence of Na+, exposure to HCO3- alone had no consistent effect on PD or pHi. In the absence of HCO3-, reexposure to Na+ depolarized cells by 3 +/- 1 mV and caused an amiloride-inhibitable increase in pHi of 0.031 +/- 0.02 units/min. In the presence of HCO3-, reexposure to Na+ hyperpolarized cells by -14 +/- 5 mV and increased pHi at a rate of 0.133 +/- 0.11 units/min; both the hyperpolarization and alkalinization were inhibited by SITS but unaffected by amiloride. These changes in PD indicate that Na(+)-coupled HCO3- transport is electrogenic, consistent with coupling of more than one HCO3- to each Na+. Furthermore, SITS-inhibitable Na(+)-dependent alkalinization exceeds amiloride-inhibitable Na(+)-dependent alkalinization by an order of magnitude, suggesting that the transport capacity of Na(+)-coupled HCO3- transport exceeds that of Na(+)-H+ exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

HCO3(-)-coupled Na+ influx is a major determinant of Na+ turnover and Na+/K+ pump activity in rat hepatocytes

Recent studies in hepatocytes indicate that Na(+)-coupled HCO3- transport contributes importantly to regulation of intracellular pH and membrane HCO3- transport. However, the direction of net coupled Na+ and HCO3- movement and the effect of HCO3- on Na+ turnover and Na+/K+ pump activity are not known. In these studies, the effect of HCO3- on Na+ influx and turnover were measured in primary rat hepatocyte cultures with 22Na+, and [Na+]i was measured in single hepatocytes using the Na(+)-sensitive fluorochrome SBFI. Na+/K+ pump activity was measured in intact perfused rat liver and hepatocyte monolayers as Na(+)-dependent or ouabain-suppressible 86Rb uptake, and was measured in single hepatocytes as the effect of transient pump inhibition by removal of extracellular K+ on membrane potential difference (PD) and [Na+]i. In hepatocyte monolayers, HCO3- increased 22Na+ entry and turnover rates by 50-65%, without measurably altering 22Na+ pool size or cell volume, and HCO3- also increased Na+/K+ pump activity by 70%. In single cells, exposure to HCO3- produced an abrupt and sustained rise in [Na+]i from approximately 8 to 12 mM. Na+/K+ pump activity assessed in single cells by PD excursions during transient K+ removal increased congruent to 2.5-fold in the presence of HCO3-, and the rise in [Na+]i produced by inhibition of the Na+/K+ pump was similarly increased congruent to 2.5-fold in the presence of HCO3-. In intact perfused rat liver, HCO3- increased both Na+/K+ pump activity and O2 consumption. These findings indicate that, in hepatocytes, net coupled Na+ and HCO3- movement is inward and represents a major determinant of Na+ influx and Na+/K+ pump activity. About half of hepatic Na+/K+ pump activity appears dedicated to recycling Na+ entering in conjunction with HCO3- to maintain [Na+]i within the physiologic range.

Effects of DuP 753 on proximal nephron and renal transport

We used the nonpeptide angiotensin II receptor antagonist DuP 753, which lacks the agonist and kinin/prostaglandin-inducing properties of saralasin and captopril, respectively, to examine the role of endogenous angiotensin II in regulating transport in the proximal convoluted tubule (PCT) and whole kidney. During in vivo microperfusion in the Munich-Wistar rat, a maximally effective dose of DuP 753 (10 mg/kg, intravenously) powerfully inhibited absorption of bicarbonate (370 +/- 3 to 200 +/- 9 pEq/mm.min, P less than .001), chloride (214 +/- 3 to 105 +/- 9 pEq/mm.min, P less than .001), and water 5.2 +/- 0.1 to 2.8 +/- 0.2 nL/mm.min, P less than .001) in the S1 subsegment of the PCT. DuP 753 was significantly more effective than captopril (3 mg/kg, intravenously) in inhibiting sodium chloride transport and is the most potent diuretic ever described in this segment. Consistent with the axial decline of angiotensin II receptor density in the PCT, DuP 753 was a less effective transport inhibitor in the S2 subsegment of the PCT, similar to captopril. Using free-flow micropuncture and clearance techniques, though inhibition in the earliest segment of the nephron is partially compensated by downstream reabsorption, DuP 753 induces a substantial diuresis, natriuresis, and chloruresis. In conclusion, DuP 753 markedly decreases S1 PCT fluid and electrolyte absorption, indicating that endogenous angiotensin II exerts significant tonic support of proximal transport in vivo.

Proximal nephron and renal effects of DuP 753, a nonpeptide angiotensin II receptor antagonist

The purpose of these studies was to quantitatively assess the role of endogenous angiotensin II activity in controlling transport in the proximal convoluted tubule (PCT) and whole nephron. We used the nonpeptide angiotensin II receptor antagonist DuP 753, which lacks the agonist and kinin/prostaglandin-inducing properties of saralasin and captopril, respectively. During in vivo microperfusion in the Munich-Wistar rat, we found that DuP 753 had a powerful inhibitory effect on bicarbonate (370 +/- 3 to 200 +/- 9 pEq/mm.min, P less than 0.001), chloride (214 +/- 3 to 105 +/- 9 pEq/mm.min, P less than 0.001), and water (5.2 +/- 0.1 to 2.8 +/- 0.2 nl/mm.min, P less than 0.001) absorption in the S1 subsegment of the PCT. At maximally effective doses, DuP 753 (10 mg/kg i.v.) was significantly more effective than was captopril (3 mg/kg i.v.) in inhibiting sodium chloride transport in the S1 PCT. DuP 753 is the most potent diuretic ever described in this segment. Consistent with the axial decline of angiotensin II receptor density in the PCT, DuP 753 was a less effective transport inhibitor in the S2 subsegment of the PCT, similar to captopril. Though downstream reabsorptive elements partially compensate for the action in the earliest segment of the nephron, we also showed using free-flow micropuncture and clearance techniques that DuP 753 induces a substantial diuresis, natriuresis and chloruresis. In conclusion, the marked decrease in S1 PCT fluid and electrolyte absorption induced by DuP 753 indicates that endogenous angiotensin II exerts significant tonic support of proximal transport in vivo.

Na(+)-Ca2+ exchange in cultured rat hepatocytes: evidence against a role in cytosolic Ca2+ regulation or signaling

Plasma membrane Na(+)-Ca2+ exchange contributes importantly to the regulation of cytosolic Ca2+ concentration ([Ca2+]i) in excitable cells. Despite extensive study in excitable tissues, the role of this transporter in the regulation of [Ca2+]i in hepatocytes is unknown, and conflicting information has been reported regarding the presence of Na(+)-Ca2+ exchange in hepatocyte plasma membrane vesicles. We have therefore assessed the role of Na(+)-dependent Ca2+ transport in the regulation of [Ca2+]i in rat hepatocytes in primary culture under basal conditions and after exposure to vasopressin, a hormone that elevates [Ca2+]i. Ca2+ efflux, measured using 45Ca, did not differ in the presence or absence of extracellular Na+, either under basal conditions or in response to vasopressin. [Ca2+]i, measured using the Ca2(+)-sensitive dye fura-2, was not altered by transient or prolonged exposure to Na(+)-free media or by exposure to ouabain in concentrations sufficient to produce a five-fold elevation in intracellular Na+ concentration. The [Ca2+]i response to vasopressin was also unaffected by Na+ removal or ouabain. By contrast, in cultured rat cardiac myocytes, cells that possess Na(+)-Ca2+ exchange, transient or prolonged Na+ removal as well as ouabain exposure produced greater than fivefold increases in [Ca2+]i compared with controls. We conclude that Na(+)-Ca2+ exchange does not contribute to the regulation of [Ca2+]i in hepatocytes.

Urinary cGMP as biological marker of the renal activity of atrial natriuretic factor

Current evidence suggests guanosine 3',5'-cyclic monophosphate (cGMP) serves as the second messenger for atrial natriuretic factor (ANF) in the kidney in vivo. We examined whether extracellular cGMP accumulation quantitatively reflected the concentration of cGMP within renal cells and whether urinary excretion of cGMP correlated with the physiological action of ANF. cGMP egression was examined in renal epithelial LLC-PK1 cells. ANF augmented intracellular cGMP concentration and extracellular cGMP appearance. Extracellular cGMP was an excellent function of the time-integrated intracellular cGMP concentration. In clearance studies in awake rats, urinary cGMP was primarily of renal cellular origin and correlated with the natriuresis induced by ANF in a time-dependent and concentration-dependent fashion. Urinary cGMP excretion may be useful as a biological marker for the renal activity of ANF in vivo.