[Effect of GTPase activating protein Git2 on metastasis in breast cancer]

OBJECTIVE

To investigate the effect of GTPase activating protein Git2 on metastasis in breast cancer.

METHODS

Git2 gene over-expression was induced by Git2 cDNA, and Git2 gene knockdown was induced by Git2 ShRNA lentivirus in four breast cancer cell lines. Six-week old wide type female mice were also used in this study. The cells were tagged with luciferase and injected into wide type female mice by tail vein or 4(th) mammary fat pad, respectively, to establish a cancer metastasis model. In vivo real time imaging system and immunohistochemical staining were used to detect the cancer metastasis.

RESULTS

The relative mRNA expression level of Git2 (normalized by GAPDH) in the 4T1, 4TO7, 168FARN and 67NR cells were 0.91±0.03, 0.125±0.06, 0.131±0.04 and 0.92±0.04, respectively. The expression of EMT marker E-cadherin was inhibited and N-cadherin and vimentin were enhanced when Git2 was over-expressed in 168FARN cells and 4TO7 cells expressing low level of Git2, whereas the expression of E-cadherin was increased and N-cadherin and vimentin were decreased when Git2 was knocked down in 67NR cells and 4T1 cells expressing high level of Git2. Furthermore, over-expression of Git2 promoted 4TO7 cells to progress from micro-metastasis to macro-metastasis. The down-regulation of Git2 pushed 67NR cells to intravasate into blood circulation and suppressed the metastatic ability of 4T1 cells. The number of bioluminescence photos of lung metastatic 4T1-Luc-KD cells was (0.4±0.05)×10(6,) compared with (3.0±0.04)×10(6) in the control 4T1-Luc cells, showing a significant difference (P<0.05).

CONCLUSION

Our results indicate that Git2 is involved in breast cancer initiation and metastatic colonization.

Correlation between polymorphisms in the visfatin gene and its expression in the serum and coronary artery calcification

We investigated the association between serum visfatin levels and single nucleotide polymorphisms (SNPs; rs61330082, rs2058539) in the visfatin gene and coronary artery calcification (CAC) in patients from Wenzhou, China. CAC patients (N = 206) were divided into two groups: mild CAC (MCAC) and moderate and severe CAC (MSCAC). Volunteers without CAC (N = 70) were included in the control group. The serum visfatin level was analyzed by enzyme-linked immunosorbent assay. SNPs (rs61330082, rs2058539) in the visfatin gene were analyzed by polymerase chain reaction-restriction fragment length polymorphism. Clinical data, serum visfatin levels, and genotype and allele frequencies of rs61330082 and rs2058539 were compared among the three groups. MSCAC patients expressed significantly higher serum visfatin levels (30.58 ± 6.12 ng/mL) than individuals in the MCAC (29.03 ± 1.87 ng/mL) and control (24.45 ± 5.44 ng/mL) groups (P < 0.05). The genotype distributions and frequencies of rs61330082 differed significantly among the groups (P < 0.05), while those of rs2058539 did not. The serum visfatin level was positively correlated with the body mass index (BMI), high-density lipoprotein cholesterol (HDL-C), and insulin resistance index (IRI), and negatively correlated with the triglyceride (TG) levels (P < 0.05) of patients. Serum visfatin is associated with the development of CAC. The T allele of the rs61330082 SNP in the visfatin gene had a cardioprotective effect on patients with CAC; the SNP at rs2058539 was not significantly associated with CAC. The BMI, HDL-C, IRI, and TG levels influenced the development of CAC.

Relationship between HLA-DP gene polymorphisms and the risk of hepatocellular carcinoma: a meta-analysis

The association between the HLA-DP single nucleotide polymorphisms (SNPs) rs3077 and rs9277535 and hepatocellular carcinoma (HCC) has been reported, but results have been inconclusive and controversial. Therefore, to investigate the relationship between these HLA-DP SNPs and HCC susceptibility, a meta-analysis of studies published before January 2014 was carried out using the PubMed and Google Scholar databases. Odds ratios (ORs) and 95% confidence intervals (CI) were calculated for HLA-DP alleles, and for co-dominant, dominant, and recessive genotype models of each SNP, based on fixed- or random-effects models. A total of nine studies from six published articles were included. The association study between rs3077 and HCC susceptibility was performed in four independent comparisons that contained 1871 cases with hepatitis B virus (HBV)-related HCC and 3207 carriers with persistent HBV. Association between rs9277535 and HCC susceptibility was examined in five separate comparisons that contained 2017 cases and 3930 carriers. Our analysis indicated a significant association of rs3077 and rs9277535 with HCC susceptibility, suggesting that rs3077 might act beneficially against HCC susceptibility (A vs G: OR = 0.884, 95%CI = 0.803-0.973, P = 0.012; GA vs GG: OR = 0.842, 95%CI = 0.733-0.967, P = 0.015; AA+GA vs GG: OR = 0.848, 95%CI = 0.744-0.968, P = 0.014), and that rs9277535 might promote HCC susceptibility (AA vs GA: OR = 1.202, 95%CI = 1.011-1.428, P = 0.037). This study suggested that HLA-DP rs3077 and rs9277535 polymorphisms are associated with HCC susceptibility in the Asian population.

A promoter polymorphism (rs3806798) of interleukin-15 gene is associated with chronic hepatitis B virus infection in the Chinese Han population

This study aimed to investigate the association between the polymorphisms of IL-15 gene and susceptibility to chronic hepatitis B virus (HBV) infection in the Chinese Han population. A total of 234 patients with chronic HBV infection and 150 age- and sex-matched healthy controls in the Chinese population were enrolled in this case-control study. Genotyping of ten single nucleotide polymorphisms (SNPs) in the IL-15 gene was carried out via Sequenom MassARRAY system. The association analysis demonstrated that SNP rs3806798 (A/T) had a significant difference in the distribution between patients and healthy controls (P = 0.033). Moreover, a significantly increased risk of HBV infection was found to be associated with IL-15 rs3806798 A allele among male patients and HBeAg-negative patients, compared with IL-15 rs3806798 T allele (P = 0.003; P = 0.046, respectively). Furthermore, haplotype analysis revealed that haplotype ATAGG (rs3806798, rs12508866, rs1519551, rs6819823 and rs2857261, respectively) in block 1 was significantly associated with HBV infection (P = 0.022). In conclusion, we found an association between IL-15 rs3806798 and the risk of chronic HBV infection in a sample of Chinese Han population.

General practice education and training in southern China: recent development and ongoing challenges under the health care reform

China has launched a general practice (GP)-orientated primary care reform in 2009 to develop a more productive, coordinated, and cost-effective system to maintain and improve the health and well-being of one-fifth of the world population. The restructure of the health care system with a focus on primary care requires practitioners working on GP as gatekeepers for service delivery that is responsive to the needs of people. It is particularly prioritised to establish a sound education and training system to ensure that the competencies of practitioners are aligned with local health care needs. This article aims to provide a brief review of the development of GP, including exemplary model of education and training currently implemented in southern China, as well as the challenges to be addressed in the next step. There is a shortage of well-trained and qualified general practitioners in China where more than half of the licensed clinicians in primary care are educated below the undergraduate level. Although there is a stepwise increase in recognition that the capacity of GP is pivotal to the success of primary care development in China, challenges coming from resource restriction, rural and urban disparity, social attitude, and community involvement are highlighted as major bottlenecks that currently hinder the rapid development of GP in China. Supportive policy and guidelines are necessary to build up strong GP recognition and ensure adequate resources to underpin a robust primary care system to deliver affordable and effective health care services for the world's largest population. It might share some similar experiences with other countries that are struggling to develop a GP-based primary care system.

Protein transduction domain-hA20 fusion protein protects endothelial cells against high glucose-induced injury

We constructed a plasmid containing a protein transduction domain (PTD) and a human A20 (hA20) gene fragment; the fusion protein was obtained by highly expressing this plasmid in the yeast Pichia pastoris GS115. The plasmid was obtained by adding 9xArg and EcoRІ recognition sites to the end of the primer, and 6xHis-Tag and NotІ recognition sites to its end. After sequencing, the hA20 gene fragment was inserted into plasmid pPIC9k to construct expression vector pPIC9k-PTD-hA20; then, we transfected GS115 with the vector and induced PTD-hA20 protein expression. We purified protein from the yeast fermentation supernatant using a nickel column. Human umbilical vein endothelial cells (HUVECs) were cultured in high glucose medium (30 mM glucose) and in high glucose medium containing different concentrations of protein. Apoptosis of HUVECs was assayed by TUNEL 72 h later. The biological activity tests indicated that the fusion protein not only passed through the cell membrane freely, but also inhibited apoptosis of HUVECs induced by high glucose levels. We conclude that the fusion protein PTD-hA20 has potential for clinical use.

Zinc finger protein A20 overexpression inhibits monocyte homing and protects endothelial cells from injury induced by high glucose

Diabetes mellitus causes vascular lesions and may ultimately lead to atherosclerosis. One of the earliest steps in the development of atherosclerotic lesions is the adhesion of monocytes to endothelial cells of the vessel wall. It is currently unknown whether zinc finger protein A20 is able to protect endothelial cells from injury caused by high levels of glucose and monocyte homing. In our study, adhesion of monocytes to the vessel wall endothelium was detected by measuring the rolling velocity of monocytes along human umbilical vein endothelial cells (HUVECs). Activation of NF-κB was analyzed through Western blot. HUVEC apoptosis was monitored by TUNEL in situ end-labeling and flow cytometry. High glucose concentrations (25 mM) stimulated monocytes, reducing the velocity at which they roll along HUVECs. Stimulation of monocytes with high levels of glucose also induced HUVEC apoptosis. Overexpression of the zinc finger protein A20 inhibited monocyte recruitment, NF-κB activation, P-selectin expression, and HUVEC apoptosis induced by high glucose levels. We conclude that zinc finger protein A20 can protect HUVECs from injury induced by high levels of glucose and potentially could be used to develop treatments against diabetic vascular lesions.

The structure of the bacterial and archaeal community in a biogas digester as revealed by denaturing gradient gel electrophoresis and 16S rDNA sequencing analysis

AIMS

To identify the bacterial and archaeal composition in a mesophilic biogas digester treating pig manure and to compare the consistency of two 16S rDNA-based methods to investigate the microbial structure.

METHODS AND RESULTS

Sixty-nine bacterial operational taxonomic units (OTU) and 25 archaeal OTU were identified by sequencing two 16S rDNA clone libraries. Most bacterial OTU were identified as phyla of Firmicutes (47.2% of total clones), Bacteroides (35.4%) and Spirochaetes (13.2%). Methanoculleus bourgensis (29.0%), Methanosarcina barkeri (27.4%) and Methanospirillum hungatei (10.8%) were the dominant methanogens. Only 9% of bacterial and 20% of archaeal OTU matched cultured isolates at a similarity index of >or=97%. About 78% of the dominant bacterial (with abundance >3%) and 83% of archaeal OTU were recovered from the denaturing gradient gel electrophoresis (DGGE) bands of V3 regions in 16S rDNAs.

CONCLUSIONS

In the digester, most bacterial and archaeal species were uncultured; bacteria belonging to Firmicutes, Bacteroides and Spirochaetes seem to take charge of cellulolysis, proteolysis, acidogenesis, sulfur-reducing and homoacetogenesis; the most methanogens were typical hydrogenotrophic or hydrogenotrophic/aceticlastic; DGGE profiles reflected the dominant microbiota.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study gave a first insight of the overall microbial structure in a rural biogas digester and also indicated DGGE was useful in displaying its dominant microbiota.

Bacterial and archaeal assemblages in sediments of a large shallow freshwater lake, Lake Taihu, as revealed by denaturing gradient gel electrophoresis

AIMS

To explore the association of microbial community structure with the development of eutrophication in a large shallow freshwater lake, Lake Taihu.

METHODS AND RESULTS

The bacterial and archaeal assemblages in sediments of different lake areas were analysed using denaturing gradient gel electrophoresis (DGGE) of amplified 16S rDNA fragments. The bacterial DGGE profiles showed that eutrophied sites, grass-bottom areas and relatively clean sites with a eutrophic (albeit dredged) site are three respective clusters. Fifty-one dominant bacterial DGGE bands were detected and 92 corresponding clones were sequenced, most of which were affiliated with bacterial phylotypes commonly found in freshwater ecosystems. Actinobacteria were detected in the centre of the lake and not at eutrophied sites whereas the opposite was found with respect to Verrucomicrobiales. Twenty-five dominant archaeal DGGE bands were detected and 31 corresponding clones were sequenced, most of which were affiliated with freshwater archaeal phylotypes.

CONCLUSIONS

The bacterial community structures in the sediments of different areas with similar water quality and situation tend to be similar in Taihu Lake.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study may expand our knowledge on the relationship between the overall microbial assemblages and the development of eutrophication in the shallow freshwater lake.

Structure comparisons of Aedes albopictus densovirus with other parvoviruses

Parvoviridae is a family of the smallest viruses known with a wide variety of hosts. The capsid structure of the Aedes albopictus C6/36 cell densovirus (C6/36 DNV) at 1.2-nm resolution was obtained by electron cryomicroscopy (cryoEM) and three-dimensional (3D) image reconstruction. Structure comparisons between the C6/36 DNV and other parvoviruses reveal that the degree of structural similarity between C6/36 DNV and the human parvovirus B19 is higher than that between C6/36 DNV and other insect parvoviruses. The amino acid sequence comparisons of structural and non-structural proteins also reveal higher levels of similarity between C6/36 DNV and parvovirus B19 than those between C6/36 DNV and other parvoviruses. These findings indicate that C6/36 DNV is closely related to the human virus B19, and the former might evolve from the human species other than from other insect viruses.

Consequences of deterministic and stochastic modeling of a promoter

For an engineered genetic oscillator, deterministic analysis indicates sustained oscillations and stochastic simulations show irregular or absent oscillations. Since the major difference is in the modeling of the promoters, we have performed a detailed analysis of a generic repressible promoter system. Deterministic, stochastic, thermodynamic, and hybrid models were developed for the promoter. The average behavior of the stochastic model converged to the thermodynamic model. The deterministic model is a special case of the thermodynamic model. The hybrid model could lock into the off state. Adding an unrelated background reaction allowed it to exit that state. Increasing the background rate allowed the hybrid model to converge to thermodynamic and stochastic model. Adding a background reaction to the stochastic oscillator simulation noticeably improved its performance.

3D reconstruction and capsid protein characterization of grass carp reovirus

Grass carp reovirus (GCRV) is a relatively new virus first isolated in China and is a member of the Aquareovirus genus of the Reoviridae family. Recent report of genomic sequencing showed that GCRV shared high degree of homology with mammalian reovirus (MRV). As a step of our effort to understand the structural basis of GCRV pathogenesis, we determined the three-dimensional (3D) structure of GCRV capsid at 17 A resolution by electron cryomicroscopy. Each GCRV capsid has a multilayered organization, consisting of an RNA core, an inner, middle and outer protein layer. The outer layer is made up of 200 trimers that are arranged on an incomplete T=13 icosahedral lattice. A characteristic feature of this layer is the depression resulting from the absence of trimers around the peripentonal positions, revealing the underlying trimers on the middle layer. There are 120 subunits in the inner layer arranged with T=1 symmetry. These structural features are common to other members of the Reoviridae. Moreover, SDS-PAGE analysis showed that GCRV virions contain seven structural proteins (VP1-VP7). These structural proteins have a high degree of sequence homology to MRV, consistent with the structural similarities observed in our study. The high structural similarities of isolated GCRV and MRV suggest that future structural studies focusing on GCRV entering into and replicating within its host cell are necessary in order to fully understand the structural basis of GCRV pathogenesis.

Three-dimensional structure determination of capsid of Aedes albopictus C6/36 cell densovirus

The three-dimensional structure of capsid of Aedes albopictus C6/36 densovirus was determined to 14-A resolution by electron cryomicroscopy and computer reconstruction. The triangulation number of the capsid is 1. There are 12 holes in each triangular face and a spike on each 5-fold vertex. The validity of the capsid and nucleic acid densities in the reconstructions was discussed.

Genetic, biochemical, and structural characterization of a new densovirus isolated from a chronically infected Aedes albopictus C6/36 cell line

We report the isolation, sequencing, biochemical, and structural characterization of a previously undescribed virus in a chronically infected Aedes albopictus C6/36 cell line. This virus is identified as a new densovirus under the Densovirinae subfamily of the Parvoviridae based on its biological and morphologic properties as well as sequence homologies, and is tentatively designated A. albopictus C6/36 cell densovirus (C6/36 DNV). Analysis of the 4094 nt of the C6/36 DNV genome revealed that the plus strand had three large open reading frames (ORFs): a left ORF, a right ORF, and a mid-ORF (within the left ORF), whose potential coding capacities are 91.0, 40.8, and 41.2 kDa, respectively. The left ORF likely encodes the nonstructural protein NS-1, which contains NTP-binding and helicase domains. The right ORF likely encodes structural proteins, VP1 and VP2. Our analyses revealed that C6/36 DNV has a similar genomic organization and shares very high homology in nucleotide sequence and amino acid sequences with Aedes aegypti densovirus (AaeDNV) and A. albopictus densovirus (AalDNV), members of the genus Brevidensovirus of the Densovirinae. Similar to other densoviruses, C6/36 DNV has a different genomic organization and no recognizable sequence homology with viruses in the Parvovirinae. The three-dimensional (3D) reconstruction of the C6/36 DNV at 15.6-A resolution by electron cryomicroscopy (cryoEM) revealed distinctive outer surface features not previously seen in other parvoviruses, indicating structural divergence of densoviruses, in addition to its genomic differences, while the inner surface of the C6/36 DNV capsid exhibits features that are conserved among parvoviruses.

Two-photon induced blue fluorescent emission of heterocycle-based organic molecule

An organic molecule based on a heterocycle acceptor has been found to exhibit an intensive two-photon induced blue emission and a large two-photon absorption cross section, which implies that the molecule is a promising candidate for an application such as multi-channel two-photon microscopy.

The remarkable structural and functional organization of the eukaryotic pyruvate dehydrogenase complexes

The three-dimensional reconstruction of the bovine kidney pyruvate dehydrogenase complex (M(r) approximately 7.8 x 10(6)) comprising about 22 molecules of pyruvate dehydrogenase (E(1)) and about 6 molecules of dihydrolipoamide dehydrogenase (E(3)) with its binding protein associated with the 60-subunit dihydrolipoamide acetyltransferase (E(2)) core provides considerable insight into the structural and functional organization of the largest multienzyme complex known. The structure shows that potentially 60 centers for acetyl-CoA synthesis are organized in sets of three at each of the 20 vertices of the pentagonal dodecahedral core. These centers consist of three E(1) molecules bound to one E(2) trimer adjacent to an E(3) molecule in each of 12 pentagonal openings. The E(1) components are anchored to the E(1)-binding domain of the E(2) subunits through an approximately 50-A-long linker. Three of these linkers emanate from the outside edges of the triangular base of the E(2) trimer and form a cage around its base that may shelter the lipoyl domains and the E(1) and E(2) active sites. The docking of the atomic structures of E(1) and the E(1) binding and lipoyl domains of E(2) in the electron microscopy map gives a good fit and indicates that the E(1) active site is approximately 95 A above the base of the trimer. We propose that the lipoyl domains and its tether (swinging arm) rotate about the E(1)-binding domain of E(2,) which is centrally located 45-50 A from the E(1), E(2), and E(3) active sites, and that the highly flexible breathing core augments the transfer of intermediates between active sites.

The pattern of tegument-capsid interaction in the herpes simplex virus type 1 virion is not influenced by the small hexon-associated protein VP26

Examination of the three-dimensional structure of intact herpes simplex virus type 1 (HSV-1) virions had revealed that the icosahedrally symmetrical interaction between the tegument and capsid involves the pentons but not the hexons (Z. H. Zhou, D. H. Chen, J. Jakana, F. J. Rixon, and W. Chiu, J. Virol. 73:3210-3218, 1999). To account for this, we postulated that the presence of the small capsid protein, VP26, on top of the hexons was masking potential binding sites and preventing tegument attachment. We have now tested this hypothesis by determining the structure of virions lacking VP26. Apart from the obvious absence of VP26 from the capsids, the structures of the VP26 minus and wild-type virions were essentially identical. Notably, they showed the same tegument attachment patterns, thereby demonstrating that VP26 is not responsible for the divergent tegument binding properties of pentons and hexons.

Improvement of preservation with cardioplegic solution by nitroglycerin-induced delayed preconditioning is mediated by calcitonin gene-related peptide

Improvement of preservation with cardioplegic solution by nitroglycerin-induced delayed preconditioning was studied in the isolated rat heart. The isolated rat heart was arrested using St. Thomas Hospital solution, and then reperfused with normothermic Krebs-Henseleit solution for 40 min after a 4-h hypothermic ischemic period. Heart rate, coronary flow, left ventricular pressure and the maximum value of the first derivatives of left ventricular pressure (+/-dp/dt(max)) were recorded, and plasma concentrations of CGRP-like immunoreactivity (CGRP-LI) and nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha) in myocardial tissues, and creatine kinase in coronary effluent were measured. Delayed preconditioning was induced by i.v. injection of nitroglycerin 24 h before the experiment. Nitroglycerin (60 microg/kg or 120 microg/kg) caused an improvement of cardiac function, a decrease in the release of creatine kinase in coronary effluent and a decrease in the content of TNF-alpha in myocardial tissues. Nitroglycerin significantly increased plasma concentrations of CGRP and NO. After pretreatment with capsaicin, which depletes neurotransmitters in sensory nerves, or methylene blue, a selective guanylate cyclase inhibitor, the protection and the elevated release of CGRP induced by nitroglycerin were abolished. The present study suggests that improvement of preservation with cardioplegic solution by nitroglycerin-induced delayed preconditioning is due to stimulation of CGRP release in the rat heart, and that the protection of CGRP-mediated nitroglycerin is related to inhibition of TNF-alpha production.

Hyperactive ENaC identifies hypertensive individuals amenable to amiloride therapy

Pathophysiological features of both primary aldosteronism and pseudohyperaldosteronism are hyperactive amiloride-sensitive epithelial Na(+) channels (ENaC) and refractory hypertension. Peripheral blood lymphocytes express ENaC, which functions and is regulated similarly to ENaC expressed by renal principal cells. Thus it was hypothesized that individuals with either of these hypertensive etiologies could be identified by assessment of the function and regulation of peripheral blood lymphocyte ENaC, by whole cell patch clamp. We also tested the hypothesis that specific inhibition of hyperactive ENaC with amiloride could ameliorate the hypertension. To test these hypotheses, we solicited blood samples from normotensive, controlled hypertensive, and refractory hypertensive individuals. Lymphocytes were examined electrophysiologically to determine whether ENaC was hyperactive. All positive findings were from refractory hypertensive individuals. Nine refractory hypertensive patients had amiloride added to their hypertensive therapy. Amiloride normalized the blood pressure of four subjects. These individuals all had hyperactive ENaC. Amiloride had no effect on individuals with normal ENaC. These findings suggest that whole-cell patch clamp of peripheral blood lymphocytes can be used to identify accurately and rapidly hypertensive individuals who will respond to amiloride therapy.

Electron cryomicroscopy and bioinformatics suggest protein fold models for rice dwarf virus

The three-dimensional structure of rice dwarf virus was determined to 6.8 A resolution by single particle electron cryomicroscopy. By integrating the structural analysis with bioinformatics, the folds of the proteins in the double-shelled capsid were derived. In the outer shell protein, the uniquely orientated upper and lower domains are composed of similar secondary structure elements but have different relative orientations from that of bluetongue virus in the same Reoviridae family. Differences in both sequence and structure between these proteins may be important in defining virus-host interactions. The inner shell protein adopts a conformation similar to other members of Reoviridae, suggesting a common ancestor that has evolved to infect hosts ranging from plants to animals. Symmetry mismatch between the two shells results in nonequivalent, yet specific, interactions that contribute to the stability of this large macromolecular machine.

Nongenomic regulation of ENaC by aldosterone

Aldosterone is involved in salt and water homeostasis. The main effect is thought to involve genomic mechanisms. However, the existence of plasma membrane steroid receptors has been postulated. We used whole cell patch clamp to test the hypothesis that epithelial sodium channels (ENaC) expressed by renal collecting duct principal cells can be regulated nongenomically by aldosterone. In freshly isolated principal cells from rabbit, aldosterone (100 nM) rapidly (<2 min) increased ENaC sodium current specifically. The aldosterone-activated current was completely inhibited by amiloride. Aldosterone also activated ENaC in cells treated with the mineralocorticoid receptor blocker spiranolactone. Nongenomic activation was inhibited by inclusion of S-adenosyl-L-homocysteine in the pipette solution, which inhibits methylation reactions. Also, the nongenomic activation required 2 mM ATP supplementation in the pipette solution. Aldosterone did not activate any ENaC current in whole cell clamped rat collecting duct principal cells. These functional studies are consistent with aldosterone membrane binding studies, suggesting the presence of a plasma membrane steroid receptor that affects cellular processes by mechanisms unrelated to altered gene expression.

Involvement of calcitonin gene-related peptide in the development of tolerance to nitroglycerin in the rat

Previous studies have shown that the depressor effect of nitroglycerin is related to stimulation of endogenous calcitonin gene-related peptide (CGRP) release. In the present study, we explored whether endogenous CGRP is involved in the development of tolerance to nitroglycerin in the rat. Tolerance was induced by treatment with nitroglycerin (10 mg/kg, subcutaneous [s.c.]) three times a day for 8 days and confirmed by a reduction in hypotensive responses to intravenous (i.v.) nitroglycerin. Nitroglycerin (30 or 150 microg/kg, i.v.) significantly decreased blood pressure concomitantly with an increase in plasma concentration of nitric oxide (NO) and CGRP, and these effects of nitroglycerin disappeared after pretreatment with nitroglycerin for 8 days. However, the nitroglycerin-induced depressor effect and elevation of NO and CGRP content were restored, partially or completely, 4 or 8 days after nitroglycerin removal in the tolerant rat. The present study suggests that the development of tolerance to nitroglycerin is related to the decreased release of CGRP in the rat.

The depressor effect of nitroglycerin is mediated by calcitonin gene-related peptide

Previous investigations have suggested that vasodilator responses to nitroglycerin involve in stimulation of calcitonin gene-related peptide (CGRP) release. Therefore, we tested whether depressor effect of nitroglycerin is mediated by CGRP. A catheter was inserted into the left femoral artery to record blood pressure and drugs were administered through cannulae inserted into the right femoral vein. Nitroglycerin (15, 30, 60, 120 and 150 microg/kg) caused depressor effects in a dose-dependent manner. Nitroglycerin (30 or 150 microg/kg) caused a depressor effect with an increase in plasma concentrations of CGRP. The effects of nitroglycerin were significantly attenuated by methylene blue, an inhibitor of guanylate cyclase, or by pretreatment with capsaicin (50 mg x kg(-1), s.c.), which depletes neurotransmitters in sensory nerves. The present study suggests that the depressor effect of nitroglycerin is related to stimulation of CGRP release in the rat.

Repeat expansion by homologous recombination in the mouse germ line at palindromic sequences

Genetic instability can be induced by unusual DNA structures and sequence repeats. We have previously demonstrated that a large palindrome in the mouse germ line derived from transgene integration is extremely unstable and undergoes stabilizing rearrangements at high frequency, often through deletions that produce asymmetry. We have now characterized other palindrome rearrangements that arise from complex homologous recombination events. The structure of the recombinants is consistent with homologous recombination occurring by a noncrossover gene conversion mechanism in which a break induced in the palindrome promotes homologous strand invasion and repair synthesis, similar to mitotic break repair events reported in mammalian cells. Some of the homologous recombination events led to expansion in the size of the palindromic locus, which in the extreme case more than doubled the number of repeats. These results may have implications for instability observed at naturally occurring palindromic or quasipalindromic sequences.