Evidence that epithelial glycoprotein 330/megalin mediates uptake of polybasic drugs

Glycoprotein 330 (gp330) is an endocytic receptor expressed in the renal proximal tubules and some other absorptive epithelia, e.g., in the inner ear. The present study shows that the antifibrinolytic polypeptide, aprotinin, and the nephro- and ototoxic antibiotics, aminoglycosides, and polymyxin B compete for binding of 125I-urokinase-plasminogen activator inhibitor type-1 complexes to purified rabbit gp330. Half maximal inhibition was measured at 4 microM for aprotinin, 50 microM for gentamicin, and 0.5 microM for polymyxin B. Drug binding to gp330 was validated by equilibrium dialysis of [3H] gentamicin-gp330 incubations and binding/uptake studies in rat proximal tubules and gp330-expressing L2 carcinoma cells. Analyses of mutant aprotinins expressed in Saccharomyces cerevisiae revealed that basic residues are essential for the binding to gp330 and renal uptake. The polybasic drugs also antagonized ligand binding to the human alpha 2-macroglobulin receptor. However, the rapid glomerular filtration of the drugs suggests kidney gp330 to be the quantitatively most important target. In conclusion, a novel role of gp330 as a drug receptor is demonstrated. The new insight into the mechanism of epithelial uptake of polybasic drugs might provide a basis for future design of drugs with reduced toxicity.

The basic-helix-loop-helix protein pod1 is critically important for kidney and lung organogenesis

Epithelial-mesenchymal interactions are required for the development of all solid organs but few molecular mechanisms that underlie these interactions have been identified. Pod1 is a basic-helix-loop-helix (bHLH) transcription factor that is highly expressed in the mesenchyme of developing organs that include the lung, kidney, gut and heart and in glomerular visceral epithelial cells (podocytes). To determine the function of Pod1 in vivo, we have generated a lacZ-expressing null Pod1 allele. Null mutant mice are born but die in the perinatal period with severely hypoplastic lungs and kidneys that lack alveoli and mature glomeruli. Although Pod1 is exclusively expressed in the mesenchyme and podocytes, major defects are observed in the adjacent epithelia and include abnormalities in epithelial differentiation and branching morphogenesis. Pod1 therefore appears to be essential for regulating properties of the mesenchyme that are critically important for lung and kidney morphogenesis. Defects specific to later specialized cell types where Pod1 is expressed, such as the podocytes, were also observed, suggesting that this transcription factor may play multiple roles in kidney morphogenesis.

The intrinsic factor-vitamin B12 receptor, cubilin, is a high-affinity apolipoprotein A-I receptor facilitating endocytosis of high-density lipoprotein

Cubilin is the intestinal receptor for the endocytosis of intrinsic factor-vitamin B12. However, several lines of evidence, including a high expression in kidney and yolk sac, indicate it may have additional functions. We isolated apolipoprotein A-I (apoA-I), the main protein of high-density lipoprotein (HDL), using cubilin affinity chromatography. Surface plasmon resonance analysis demonstrated a high-affinity binding of apoA-I and HDL to cubilin, and cubilin-expressing yolk sac cells showed efficient 125I-HDL endocytosis that could be inhibited by IgG antibodies against apoA-I and cubilin. The physiological relevance of the cubilin-apoA-I interaction was further emphasized by urinary apoA-I loss in some known cases of functional cubilin deficiency. Therefore, cubilin is a receptor in epithelial apoA-I/HDL metabolism.

Impaired GABA synthesis, uptake and release are associated with depression-like behaviors induced by chronic mild stress

Major depression is a prevalent emotion disorder. Chronic stressful life in genetically susceptible individuals is presumably a major etiology that leads to neuron and synapse atrophy in the limbic system. Molecular mechanisms underlying the pathological changes remain elusive. Mice were treated by chronic unpredictable mild stress (CUMS) until they demonstrated depression-like behavior. GABA release in the medial prefrontal cortex was evaluated by cell electrophysiology and imaging. Molecular profiles related to GABA synthesis and uptake were investigated by the high-throughput sequencings of microRNAs and mRNAs as well as western blot analysis in this cortical area. In CUMS-induced depression mice, there appear the decreases in the innervation and function of GABAergic axons and in the levels of mRNAs and proteins of glutamate decarboxylase-67, vesicular GABA transporter and GABA transporter-3. miRNA-15b-5p, miRNA-144-3p, miRNA-582-5p and miRNA-879-5p that directly downregulate such mRNAs increase in this cortex. Our results suggest that chronic mild stress impairs GABA release and uptake by upregulating miRNAs and downregulating mRNAs and proteins, which may constitute the subcellular and molecular mechanisms for the lowered GABA tone in major depression.

Upregulation of microRNA-210 regulates renal angiogenesis mediated by activation of VEGF signaling pathway under ischemia/perfusion injury in vivo and in vitro

BACKGROUND

MicroRNAs (miRNAs) are endogenous, non-coding, small RNAs that regulate gene expression and function, but little is known about regulation of miRNAs in the kidneys under normal or pathologic conditions. Here, we sought to investigate the potential involvement of miRNAs in renal ischemia/reperfusion (I/R) injury and angiogenesis and to define some of the miRNAs possibly associated with renal angiogenesis.

METHODS AND RESULTS

Male Balb/c mice were subjected to a standard renal I/R. CD31 immunostaining indicated a significant increase of microvessels in the ischemic region. VEGF and VEGFR2 expression were increased in renal I/R at both the mRNA and protein levels which were detected by qRT-PCR and Western blot, respectively. More importantly, 76 microRNAs exhibited more than 2-fold changes using Agilent microRNA microarray, which contains downregulation of 40 miRNAs and upregulation of 36 miRNAs. Upregulation of miR-210 was confirmed by qRT-PCR with prominent changes at 4 and 24 h after reperfusion. Furthermore, overexpression of miR-210 in HUVEC-12 cells enhances VEGF and VEGFR2 expression and promotes angiogenesis on Matrigel in vitro.

CONCLUSION

These findings suggest miR-210 may be involved in targeting the VEGF signaling pathway to regulate angiogenesis after renal I/R injury, which provides novel insights into the angiogenesis mechanism of renal I/R injury.

Determination of Total Dietary Fiber (CODEX Definition) by Enzymatic-Gravimetric Method and Liquid Chromatography: Collaborative Study

A method for the determination of total dietary fiber (TDF), as defined by the CODEX Alimentarius, was validated in foods. Based upon the principles of AOAC Official MethodsSM 985.29, 991.43, 2001.03, and 2002.02, the method quantitates high- and low-molecular-weight dietary fiber (HMWDF and LMWDF, respectively). In 2007, McCleary described a method of extended enzymatic digestion at 37C to simulate human intestinal digestion followed by gravimetric isolation and quantitation of HMWDF and the use of LC to quantitate low-molecular-weight soluble dietary fiber (LMWSDF). The method thus quantitates the complete range of dietary fiber components from resistant starch (by utilizing the digestion conditions of AOAC Method 2002.02) to digestion resistant oligosaccharides (by incorporating the deionization and LC procedures of AOAC Method 2001.03). The method was evaluated through an AOAC collaborative study. Eighteen laboratories participated with 16 laboratories returning valid assay data for 16 test portions (eight blind duplicates) consisting of samples with a range of traditional dietary fiber, resistant starch, and nondigestible oligosaccharides. The dietary fiber content of the eight test pairs ranged from 11.57 to 47.83. Digestion of samples under the conditions of AOAC Method 2002.02 followed by the isolation and gravimetric procedures of AOAC Methods 985.29 and 991.43 results in quantitation of HMWDF. The filtrate from the quantitation of HMWDF is concentrated, deionized, concentrated again, and analyzed by LC to determine the LMWSDF, i.e., all nondigestible oligosaccharides of degree of polymerization 3. TDF is calculated as the sum of HMWDF and LMWSDF. Repeatability standard deviations (sr) ranged from 0.41 to 1.43, and reproducibility standard deviations (sR) ranged from 1.18 to 5.44. These results are comparable to other official dietary fiber methods, and the method is recommended for adoption as Official First Action.

Megalin/gp330 mediates uptake of albumin in renal proximal tubule

Serum albumin filtered in renal glomeruli is reabsorbed very efficiently in the proximal tubule by endocytosis. The present study was undertaken to determine whether megalin/gp330 binds and mediates endocytosis of albumin. Rat serum albumin (RSA) labeled with 125I and colloidal gold particles labeled with bovine serum albumin (BSA) were microinfused into rat surface proximal tubules in vivo, and tubular uptake was determined in the presence or absence of different substances known to interfere with ligand binding to megalin. Binding of 125I-BSA and 125I-RSA to purified megalin was also determined directly using Sepharose columns. The results revealed that the tubular uptake of 125I-labeled RSA was significantly inhibited by receptor-associated protein (RAP), which reduced the uptake by > 50% and by cold RSA. The uptake of BSA gold by the proximal tubule was very intensive. BSA gold was found in small and large endocytic vacuoles, dense apical tubules, and in lysosomes. The uptake was reduced by RAP to 17%, by EDTA to 19%, by BSA to 16%, by megalin to 35%, by cytochrome c to 49%, and, together with gentamicin, there was virtually no uptake. Megalin-Sepharose columns bound 125I-labeled BSA as well as 125I-RSA, the binding was inhibited by RAP and EDTA, and analysis of the eluate revealed the bound tracer to be albumin. In conclusion, the present study demonstrates that megalin is a mediator of albumin reabsorption in renal proximal tubules.

A 5-week study of the pharmacokinetics and pharmacodynamics of LY2189265, a novel, long-acting glucagon-like peptide-1 analogue, in patients with type 2 diabetes

AIM

To investigate the safety, tolerability, pharmacokinetics and pharmacodynamics of LY2189265 (LY), a novel, long-acting glucagen-like peptide-1 analogue, administered once weekly to subjects with type 2 diabetes.

METHODS

This was a placebo-controlled, parallel-group, subject- and investigator-blind study of LY in subjects (N = 43) with type 2 diabetes mellitus controlled with diet and exercise alone or with a single oral antidiabetic medication. Subjects taking metformin or thiazolidinediones continued on their therapy. Subjects receiving sulfonylurea, acarbose, repaglinide or nateglinide were switched to metformin prior to enrollment. Subjects received five once-weekly doses of 0.05, 0.3, 1, 3, 5 or 8 mg. Effects on glucose, insulin and C-peptide concentrations were determined during fasting and following standard test meals. The pharmacokinetics of LY and its effects on HBA1c, glucagon, body weight, gastric emptying and safety parameters were assessed.

RESULTS

Once-weekly administration of LY significantly reduced (p < 0.01) fasting plasma glucose, 2-h post-test meal postprandial glucose and area under the curve (AUC) of glucose after test meals at doses ≥1 mg. These effects were seen after the first dose and were sustained through the weekly dosing cycle. Most doses produced statistically significant increases in insulin and C-peptide AUC when normalized for glucose AUC. Statistically significant reductions in HBA1c were observed for all dose groups except 0.3 mg. The most commonly reported adverse effects (AEs) were nausea (35 events), headache (20 events), vomiting (18 events) and diarrhoea (8 events).

CONCLUSIONS

LY showed improvement in fasting and postprandial glycaemic parameters when administered once weekly in subjects with type 2 diabetes. The pharmacokinetics and safety profiles also support further investigation of this novel agent.

Association of petrochemical exposure with spontaneous abortion

OBJECTIVES

To assess the association between petrochemical exposure and spontaneous abortion, a retrospective epidemiological study in a large petrochemical complex in Beijing, China was conducted.

METHODS

Plant employment records identified 3105 women who were married, were 20-44 years of age, and had never smoked. Of those, 3070 women (98.8%) reported at least one pregnancy. From this group, 2853 (93%) of the women participated in the study. According to their plant employment record, about 57% of these women workers reported occupational exposure to petrochemicals during the first trimester of their pregnancy. Trained interviewers administered a standardised questionnaire to this group of women and their husbands, collecting information on reproductive history, pregnancy outcomes, employment history, occupational exposure, smoking habits, alcohol consumption, indoor air pollution, and demographic variables. The results from the womens' first pregnancies were analysed.

RESULTS

There was a significantly increased risk of spontaneous abortion for women working in all of the production plants with frequent exposure to petrochemicals (8.8%; range of 5.8%-9.8%) compared with those working in nonchemical plants (2.2%; range of 0.0%-7.1%). Also, when a comparison was made between exposed and non-exposed groups within each plant, exposure to petrochemicals was consistently associated with an increased risk of spontaneous abortion. The overall odds ratio (OR) was 2.7 (95% confidence interval (95% CI) 1.8 to 3.9) after adjusting for potential confounders. When the analysis was performed with the exposure information obtained from the women' interview responses for (self reported) exposures, the estimated OR for spontaneous abortions was 2.9 (95% CI 2.0 to 4.0). The analysis was repeated by excluding those 452 women who provided inconsistent reports between recalled exposure and work history, and a comparable risk of spontaneous abortion (OR 2.9; 95% CI 2.0 to 4.4) was found. In analyses for exposure to specific chemicals, an increased risk of spontaneous abortion was found with exposure to most chemicals, and the results for benzene (OR 2.5; 95% CI 1.7 to 3.7), gasoline (OR 1.8; 95% CI 1.1 to 2.9), and hydrogen sulphide (OR 2.3; 95% CI 1.2 to 4.4) were significant.

CONCLUSION

An increased risk of spontaneous abortion was found associated with the exposure to petrochemicals, including benzene, gasoline, and hydrogen sulphide.

Analysis of a mathematical model of the effect of inhibitors on the growth of tumors

In this paper, we study a model of tumor growth in the presence of inhibitors. The tumor is assumed to be spherically symmetric and its boundary is an unknown function r=R(t). Within the tumor the concentration of nutrient and the concentration of inhibitor (drug) satisfy a system of reaction-diffusion equations. The important parameters are Lambda(0) (which depends on the tumor's parameters when no inhibitors are present), gamma which depends only on the specific properties of the inhibitor, and beta; which is the (normalized) external concentration of the inhibitor. In this paper, we give precise conditions under which there exist one dormant tumor, two dormant tumors, or none. We then prove that in the first case, the dormant tumor is globally asymptotically stable, and in the second case, if the radii of the dormant tumors are denoted by R(s)(-),R(s)(+) with R(s)(-)<R(s)(+), then the smaller one is asymptotically stable, so that lim(t-->infinity)R(t)=R(s)(-), provided the initial radius R(0) is smaller than R(s)(+); if however R(0)R(s)(+) then the initial tumor in general grows unboundedly in time. The above analysis suggests an effective strategy for treatment of tumors.

Multi-therapeutic effects of human adipose-derived mesenchymal stem cells on radiation-induced intestinal injury

Radiation-induced intestinal injuries (RIII) commonly occur in patients who suffer from pelvic or abdominal cancer. However, current management of these injuries is ineffective. Recently, mesenchymal stem cells (MSCs) have been extensively used in regenerative medicine and have achieved a high level of efficacy. In the present study, we hypothesised that human adipose-derived mesenchymal stem cells (hAd-MSCs) could be used as potential tools to heal RIII. We observed that adult Sprague-Dawley rats that received whole-abdominal irradiation benefitted from hAd-MSC injection. hAd-MSCs had RIII-healing effects, including anti-inflammation, neovascularisation and maintenance of epithelium homeostasis, as indicated by elevated serum IL-10, upregulation of vascular endothelial growth factor, basic fibroblast growth factor and epidermal growth factor in irradiated intestine, mobilisation of CD31-positive haematopoietic stem cells or haematopoietic progenitor cells, and the prolonged presence of Bmi1-positive cells within crypts. Consequently, after hAd-MSC treatment, irradiated rats survived longer than non-treated animals. These results suggest that hAd-MSCs have therapeutic potential for RIII management.

Activation of the insulin-like growth factor-I receptor inhibits tumor necrosis factor-induced cell death

The effect of insulin-like growth factor (IGF) on tumor necrosis factor (TNF)-induced cell killing was determined for mouse BALB/c3T3 fibroblasts in vitro. Cells maintained in 0.5% fetal bovine serum (FBS) were killed by TNF within 6 h in a concentration-dependent manner, an effect that was prevented by IGF-I. TNF-induced cytotoxicity of 3T3 cells that overexpress the human IGF-I receptor (p6 cells) was prevented by IGF-I alone in the absence of serum. TNF-induced cell death was associated with the morphologic features of apoptosis and the release of low-molecular-weight DNA, both of which were prevented by IGF-I. Neither epidermal growth factor (EGF) nor platelet-derived growth factor (PDGF) protected p6 cells from TNF-induced apoptosis. The specific protective action of the IGF-I receptor was demonstrated further by the marked sensitivity to TNF of embryo fibroblasts derived from mice with targeted disruption of the IGF-I receptor (R-cells) but not of fibroblasts derived from wild-type littermates or R-cells transfected with the cDNA for the human IGF-I receptor. Cycloheximide or actinomycin D markedly reduced the protection offered by IGF-I. IGF-I protection of BALB/c3T3 cells persisted for up to 5 days in the presence of PDGF and EGF, whereas IGF-I lost its effectiveness after 2 days in the absence of growth factors. IGF-I did not prevent TNF-induced release of arachidonic acid. The results demonstrate a specific role for the IGF-I receptor in the protection against TNF cytotoxicity. This action of the IGF-I receptor is mediated by protective cytosolic proteins that exhibit a high rate of turnover and whose levels are regulated principally by factors within serum other than IGF-I.

In vitro assessment of antimicrobial activity of carvacrol, thymol and cinnamaldehyde towards Salmonella serotype Typhimurium DT104: effects of pig diets and emulsification in hydrocolloids

AIMS

To determine the effect of pig diets in vitro on the antimicrobial activity of carvacrol, thymol and cinnamaldehyde, and to identify an emulsifier/stabilizer that can stabilize the essential oil (EO) components in aqueous solution and retain their antimicrobial activity in the presence of the diets.

METHODS AND RESULTS

Emulsification of essential oil components with hydrocolloid solution was achieved by blending with a Polytron. Antimicrobial activity was measured through in vitro assays to determine the inhibition of bacterial growth by measuring the optical density at 600 nm or plating on nutrition agar after incubation of the mixtures of an EO component with the culture of Salmonella serotype Typhimurium DT104 in the presence or absence of pig diets. The results generated through the in vitro assays indicated that pig diets were able to abolish the antimicrobial activity of EOs. Xanthan, fenugreek and yellow mustard gums were the best in forming stable emulsions of five different EO components among ten different plant polysaccharides and surfactants examined. Emulsification of all the EO components in the fenugreek gum solution did not alter their antimicrobial activity. However, the antimicrobial activity of geraniol was significantly reduced when emulsified with other polysaccharides and surfactants. Both fenugreek and xanthan gum solutions were unable to protect the antimicrobial activity of carvacrol and thymol when mixed with the diets. Although cinnamaldehyde required no emulsification, but a high concentration (equivalent to at least three times of minimum bactericidal concentration for cinnamon oil) to inhibit Salmonella growth significantly in the presence of the diets, emulsification in fenugreek gum appeared to be essential for cinnamaldehyde solution to retain its antimicrobial activity during storage.

CONCLUSIONS

The diets for newly weaned pigs were a significant factor limiting the antimicrobial activity of EOs and their components. Cinnamaldehyde required a high concentration to retain its antimicrobial activity in the diets, in addition to its requirement for emulsification to stabilize its activity during the storage.

SIGNIFICANCE AND IMPACT OF THE STUDY

The assay with the diets used in this study for measuring the antimicrobial activity can be used in vitro for rapid and effective screening of potential antimicrobials for swine production. This study has identified polysaccharides that are able to stabilize EO component solutions. It has also identified cinnamaldehyde for further in vivo studies that may have potential in future application in controlling Salmonella and possibly other enteric pathogens in swine production.

Enhanced CD34 expression of sinusoid-like vascular endothelial cells in hepatocellular carcinoma

The immunohistochemical expression of CD34 (human hematopoietic stem cell and endothelial cell marker) and laminin were studied in chronic liver diseases and hepatocellular carcinoma (HCC) to elucidate whether their expression reflected phenotypic differences between non-cancerous sinusoids and sinusoid-like tumor vessels. In normal liver, hepatic sinusoids were always negative for CD34 and laminin. In chronic hepatitis and cirrhosis, the two antigens were sparsely expressed in capillarized sinusoids at periportal and perinodular area. In advanced HCC, CD34 was strongly and diffusely expressed by the endothelial lining of sinusoid-like tumor vessels. However, early-stage HCC showed a wide spectrum of CD34 expression from negative to focal and diffuse, strongly positive staining in sinusoid-like vessels. Laminin was strongly expressed in advanced HCC but not in early-stage HCC. The results indicate that the enhanced expression of CD34 by sinusoidal endothelial cells may reflect the phenotypic change of endothelial cells in chronic liver diseases and HCC, and that the expression may correlate with the processes of angiogenesis induced by hepatocarcinogenesis.

Evaluation of new monoclonal anti-MyoD1 and anti-myogenin antibodies for the diagnosis of rhabdomyosarcoma

New monoclonal anti-MyoD1 and anti-myogenin antibodies were evaluated immunohistochemically to determine whether they are useful in discriminating rhabdomyosarcoma (RMS) from other soft tissue tumors in routinely processed sections. Neither MyoD1 nor myogenin was expressed in normal, mature striated muscle. In RMS, nuclear expression of MyoD1 and myogenin was found in 82 and 80% of non-overlapping cases, respectively. MyoD1 was generally expressed in small, primitive tumor cells, and larger cells exhibiting morphological evidence of skeletal muscle differentiation failed to express positive nuclear immunostaining. Positive nuclear staining for myogenin was stronger than that for MyoD1 in cases with abundant differentiated tumor cells, but was less prominent in cases in which small, primitive tumor cells predominated. No leiomyosarcomas, Ewing's sarcomas/peripheral primitive neuroectodermal tumors or other soft tissue tumors exhibited nuclear expression of MyoD1 or myogenin. In conclusion, both anti-MyoD1 and anti-myogenin antibodies are useful for diagnosing RMS and for discriminating RMS from other soft tissue tumors.

Peer relationships and suicide ideation and attempts among Chinese adolescents

BACKGROUND

Suicide is a global health concern. Therefore, studying suicide behaviour and identifying the early roots of suicide are critical. To address these issues, the present study examined (i) the association between peer relationships and suicide ideation and attempts among Chinese adolescents; and (ii) whether such associations were moderated or mediated by feeling of loneliness. We hypothesized that problems in peer relationships were positively associated with suicide ideation and attempts, and that feeling of loneliness would moderate and mediate such associations.

METHODS

The sample included 8778 Chinese adolescents from a large survey. Measures of peer relationships, suicide ideation and attempts, and feeling of loneliness were obtained through adolescents' self-reports.

RESULTS

Results from multivariate logistic regressions suggested that specific problems in peer relationships, such as lack of peer association and being victimized by bullying, were significantly related to suicide ideation and attempts. In addition, the moderating effects of feeling of loneliness on the association between peer relationships and suicide ideation and attempts were found. Finally, some gender effects were also found.

CONCLUSIONS

The present study provided strong evidence that suicide ideation and attempts were serious problems among adolescents in China, to which peer relationships played an important role. Further, feeling of loneliness acted as a moderator affecting the association between peer relationships and suicide ideation and attempts. Finally, there were some gender differences that have important implications.

Oxytocin-induced membrane hyperpolarization in pain-sensitive dorsal root ganglia neurons mediated by Ca(2+)/nNOS/NO/KATP pathway

Oxytocin (OT) plays an important role in pain modulation and antinociception in the central nervous system. However, little is known about its peripheral effects. This study was conducted to investigate the effect of OT on the electrical properties of neurons in the dorsal root ganglia (DRG) and the underlying mechanisms. DRG neurons from adult rats were acutely dissociated and cultured. Intracellular Ca(2+) was determined by fluorescent microscopy using an indicator dye. The electrical properties of DRG neurons were tested by patch-clamp recording. The oxytocin receptor (OTR) and neuronal nitric oxide synthase (nNOS) on DRG neurons were assessed with immunofluorescence assays. OTR co-localized with nNOS in most of Isolectin B4 (IB4)-binding cultured DRG neurons in rats. OT decreased the excitability, increased the outward current, and evoked the membrane hyperpolarization in cultured DRG neurons. Sodium nitroprusside (SNP), the donor of nitric oxide (NO), exerted similar effects as OT on the membrane potential of cultured DRG neurons. OT increased the production of NO in DRGs and cultured DRG neurons. Pre-treatment of the OTR antagonist atosiban or the selective nNOS inhibitor N-Propyl-l-arginine (NPLA) significantly attenuated the hyperpolarization effect evoked by OT. OT produced a concentration-dependent increase in intracellular Ca(2+) in DRG neurons that responds to capsaicin, which can be attenuated by atosiban, but not by NPLA. OT-evoked membrane hyperpolarization and increase of outward current were distinctly attenuated by glibenclamide, a blocker of ATP-sensitive K(+) (KATP) channel. OT might be an endogenous antinociceptive agent and the peripheral antinociceptive effects of OT are mediated by activation of the Ca(2+)/nNOS/NO/KATP pathway in DRG neurons.

The presence of a heterotrimeric G protein and its role in signal transduction of extracellular calmodulin in pollen germination and tube growth

The role of heterotrimeric G proteins in pollen germination, tube growth, and signal transduction of extracellular calmodulin (CaM) was examined in lily pollen. Two kinds of antibodies raised against animal Gzalpha, one against an internal sequence and the other against its N terminus, cross-reacted with the same 41-kD protein from lily pollen plasma membrane. This 41-kD protein was also specifically ADP ribosylated by pertussis toxin. Microinjection of the membrane-impermeable G protein agonist GTP-gamma-S into a pollen tube increased its growth rate, whereas microinjection of the membrane-impermeable G protein antagonist GDP-beta-S and the anti-Galpha antibody decreased pollen tube growth. The membrane-permeable G protein agonist cholera toxin stimulated pollen germination and tube growth. Anti-CaM antiserum inhibited pollen germination and tube growth, and this inhibitory effect was completely reversed by cholera toxin. The membrane-permeable heterotrimeric G protein antagonist pertussis toxin completely stopped pollen germination and tube growth. Purified CaM, when added directly to the medium of plasma membrane vesicles, significantly activated GTPase activity in plasma membrane vesicles, and this increase in GTPase activity was completely inhibited by pertussis toxin and the nonhydrolyzable GTP analogs GTP-gamma-S and guanylyl-5'-imidodiphosphate. The GTPase activity in plasma membrane vesicles was also stimulated by cholera toxin. These data suggest that heterotrimeric G proteins may be present in the pollen system where they may be involved in the signal transduction of extracellular CaM and in pollen germination and tube growth.

Identification and characterization of a glomerular-specific promoter from the human nephrin gene

Podocytes are highly specialized cells that make up a major portion of the glomerular filtration barrier in the kidney. They are also believed to play a pivotal role in the progression of chronic renal disease due to diverse causes that include diabetes (3, 20, 24) and aging (1, 7). Despite the importance of podocytes for kidney function and disease, studies of this cell type have been hindered due to a lack of model systems. Recently, the gene responsible for congenital Finnish nephropathy was identified and named nephrin (13). Nephrin expression is restricted to slit diaphragms of podocytes (11, 30). Infants with congenital Finnish nephropathy develop massive proteinuria and subsequent kidney failure due to podocyte injury. We have identified a 1.25-kb DNA fragment from the human nephrin promoter and 5'-flanking region that is capable of directing podocyte-specific expression in transgenic mice; this represents the first glomerular-specific promoter to be identified. Use of this transgene will facilitate studies of the podocyte in vivo and allow the identification of transacting factors that are required for podocyte-specific expression.

Performances and working mechanism of a novel polycarboxylate superplasticizer synthesized through changing molecular topological structure

A novel star-shaped polycarboxylate superplasticizer (SPCE) was synthesized through a simple two-step method. ¹H Nuclear Magnetic Resonance (¹H NMR) and Infrared Spectroscopy (IR) measurements were used for structural characterization. SPCE and comb-shaped polycarboxylate superplasticizer (CPCE) with same molecular weights were designed and synthesized. The cement paste containing SPCE exhibited better fluidity, fluidity retention, water reduction, 25% lower saturated dosage of PCE, 10% longer setting time, lower hydration heat, more delayed hydration heat evolution and lower amount of hydration products at early ages. Furthermore, the adsorption behavior of SPCE and CPCE in cement pastes and the zeta potential were investigated, and then the working mechanism of SPCE was theoretically explained. It is interesting that changing topological structure from comb-shape to star-shape can achieve the optimization of dispersion effect, and further improve the working effectiveness. The aims of this study are to provide a new avenue to synthesize superplasticizer with novel structure achieving the chemical diversity of superplasticizer structure, and to verify the contribution of optimizing molecular shape. This new type of superplasticizer can be used as a rheology modifying agent in fresh cement-based materials.

Rapid sample preparation method for PCR-based detection of Escherichia coli O157:H7 in ground beef

AIM

To develop an improved, rapid and sensitive sample preparation method for PCR-based detection of Escherichia coli O157:H7 in ground beef.

METHODS AND RESULTS

Fresh ground beef samples were experimentally inoculated with varying concentrations of E. coli O157:H7. PCR inhibitors were removed and bacterial cells were concentrated by filtration and centrifugation, and lysed using enzymatic digestion and successive freeze/thaw cycles. DNA was purified and concentrated via phenol/chloroform extraction and the Shiga toxin 1 gene (stx1) was amplified using PCR to evaluate the sample preparation method. Without prior enrichment of cells in broth media, the detection limit was 103 CFU g-1 beef. When a 6 h enrichment step was incorporated, the detection limit was 1 CFU g-1 beef. The total time required from beginning to end of the procedure was 12 h.

CONCLUSIONS

The sample preparation method developed here enabled substantially improved sensitivity in the PCR-based detection of E. coli O157:H7 in ground beef, as compared to previous reports.

SIGNIFICANCE AND IMPACT OF THE STUDY

Superb sensitivity, coupled with quick turn-around time, relative ease of use and cost-effectiveness, makes this a useful method for detecting E. coli O157:H7 in ground beef.

Availability of glutamate and arginine during acid challenge determines cell density-dependent survival phenotype of Escherichia coli strains

The cell density-dependent acid sensitivity phenotypes of Escherichia coli strains K-12 and O157:H7 were examined with reference to three possible mechanisms of acid resistance. There was no evidence of any diffusible substance released from dead cells which could influence the cell density-dependent acid survival phenotype. Instead, cell density-dependent acid survival phenotype was associated with induction of glutamate- and arginine-decarboxylase acid survival pathways and concomitant availability of glutamate and arginine during acid challenge.

Genetic variation within and between strains of outbred Swiss mice

The aim of this survey was to measure levels of genetic variation within and between 5 different strains of outbred Swiss mice. Ten to 15 animals from each strain (NIH, Q(S), ARC, IMVS and STUD) were typed, using allozyme electrophoresis, at 10 gene loci: Mod-1, Idh-1, Gpi-I, Es-1, Es-3, Hbb, Pep-3, Gr-1, Got-2 and Pgm-1. Polymorphic variation in at least one of the 5 strains was detected at all 10 loci. The proportion of polymorphic loci ranged from 0.3 (NIH) to 0.8 (IMVS) with a mean of 0.52. Average expected heterozygosities ranged from 0.08 (NIH) to 0.37 (IMVS) with a mean of 0.21. The inbred strain SWR was, as expected, homozygous at all 10 loci. The amount of allelic substitution between pairs of strains was quantified using Nei's genetic distance, and a dendrogram based on these genetic distances showed a close overall similarity in its branching pattern to the known genealogy of the strains. This survey showed that a considerable degree of genetic variation persists in the 5 strains examined, a level of variation similar to that previously detected by Rice and O'Brien (1980) in 3 other outbred Swiss strains.