Connexin-specific cell-to-cell transfer of short interfering RNA by gap junctions

The purpose of this study was to determine whether oligonucleotides the size of siRNA are permeable to gap junctions and whether a specific siRNA for DNA polymerase beta (pol beta) can move from one cell to another via gap junctions, thus allowing one cell to inhibit gene expression in another cell directly. To test this hypothesis, fluorescently labelled oligonucleotides (morpholinos) 12, 16 and 24 nucleotides in length were synthesized and introduced into one cell of a pair using a patch pipette. These probes moved from cell to cell through gap junctions composed of connexin 43 (Cx43). Moreover, the rate of transfer declined with increasing length of the oligonucleotide. To test whether siRNA for pol beta was permeable to gap junctions we used three cell lines: (1) NRK cells that endogenously express Cx43; (2) Mbeta16tsA cells, which express Cx32 and Cx26 but not Cx43; and (3) connexin-deficient N2A cells. NRK and Mbeta16tsA cells were each divided into two groups, one of which was stably transfected to express a small hairpin RNA (shRNA), which gives rise to siRNA that targets pol beta. These two pol beta knockdown cell lines (NRK-kcdc and Mbeta16tsA-kcdc) were co-cultured with labelled wild type, NRK-wt or Mbeta16tsA-wt cells or N2A cells. The levels of pol beta mRNA and protein were determined by semiquantitative RT-PCR and immunoblotting. Co-culture of Mbeta16tsA-kcdc cells with Mbeta16tsA-wt, N2A or NRK-wt cells had no effect on pol beta levels in these cells. Similarly, co-culture of NRK-kcdc with N2A cells had no effect on pol beta levels in the N2A cells. In contrast, co-culture of NRK-kcdc with NRK-wt cells resulted in a significant reduction in pol beta in the wt cells. The inability of Mbeta16tsA-kcdc cells to transfer siRNA is consistent with the fact that oligonucleotides of the 12 nucleotide length were not permeable to Cx32/Cx26 channels. This suggested that Cx43 but not Cx32/Cx26 channels allowed the cell-to-cell movement of the siRNA. These results support the novel hypothesis that non-hybridized and possible hybridized forms of siRNA can move between mammalian cells through connexin-specific gap junctions.

Renal impairment in cystic fibrosis patients due to repeated intravenous aminoglycoside use

Although there are reports of cases of acute renal failure occurring in cystic fibrosis (CF) patients, usually in association with the use of nephrotoxic antibiotic therapy, there have been no studies of renal function in this patient group. We hypothesized that long-term use of intravenous (IV) nephrotoxic antibiotics (aminoglycosides and colistin sulphomethate) may contribute to renal disease in CF patients. In a prospective study, we assessed creatinine clearance as an index of renal function with two techniques (24-hr urine collections and the Cockroft-Gault formula) in a group of 80 stable adult CF outpatients chronically infected with Pseudomonas aeruginosa but with no history of preceding renal disease. Using a multiple linear regression model, we evaluated their renal function in terms of their lifetime IV use of aminoglycosides and colistin. Between 31% (Cockroft-Gault formula method) and 42% (24-hr urine collection method) of patients had a creatinine clearance below normal range. Using either method, there was a strong correlation between aminoglycoside use and diminishing renal function (r=- 0.32, P=0.0055), which was potentiated by the coadministration of colistin (r=- 0.42, P <0.0002). However, there was no correlation with colistin when used in combination with other antibiotics alone (r=0.18, P=NS). Repeated IV aminoglycoside use in CF is associated with long-term renal damage. Although this effect is potentiated by colistin, colistin on its own in moderate doses does not appear to be nephrotoxic. IV aminoglycosides should be used cautiously in CF patients, with regular monitoring of renal function.

High-resolution record of Northern Hemisphere climate extending into the last interglacial period

Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5 degrees C warmer than today. We find unexpectedly large temperature differences between our new record from northern Greenland and the undisturbed sections of the cores from central Greenland, suggesting that the extent of ice in the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland. This record shows a slow decline in temperatures that marked the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw between the hemispheres (which dominated the last glacial period) was not operating at this time.

Abnormal IL-2 receptor levels in non-pregnant women with a history of recurrent miscarriage

BACKGROUND

Immunological abnormalities have been found in pregnant women with a history of recurrent miscarriage. This study compared interleukin-2 receptor (IL-2R) levels in non-pregnant women with a history of recurrent miscarriage with those found in serum from a non-pregnant group with no such history.

METHODS

Group 1 comprised 49 non-pregnant women with a history of recurrent miscarriage (at least three consecutive miscarriages). Group 2 comprised 22 non-pregnant women with no history of miscarriage. Serum IL-2R levels were measured in all patients.

RESULTS

The results obtained showed that although all women were not pregnant at the time of sampling, IL-2R levels were significantly higher in women in Group 1 compared with those in Group 2 (1589 +/- 1289 versus 1082 +/- 823 pg/ml; P < 0.05). Follow-up data were available for 21 women from Group 1. The next pregnancy ended successfully for 14 of these women, while seven miscarried again. The IL-2R levels obtained pre-pregnancy were not significantly different between the two groups (1480 +/- 910 versus 1356 +/- 716 pg/ml).

CONCLUSION

This study has shown that non-pregnant women with a history of recurrent miscarriage have raised IL-2R levels. These increased pre-pregnancy IL-2R levels did not necessarily predict miscarriage for the next pregnancy.

Application of LA-ICP-MS in polar ice core studies

The direct determination of element signatures in polar ice core samples from Greenland by laser ablation with subsequent inductively coupled plasma mass spectrometry analysis has been investigated. A cryogenic sample chamber enables the element determination in ice directly from the solid (frozen) state. A procedure was developed to analyse up to 38 elements (traces: Mg, Al, Fe, Zn, Cd, Pb and rare earth elements; minor constituents: Na) in ice samples from Greenland with a previously unachievable spatial resolution of 4 mm along the core axis. This resolution is helpful to detect seasonal variations of element concentration in thin annual layers of deep ice. We report operating conditions and analytical performance of the experimental set up, the improvement of signal stability by (17)OH internal standardisation and application of a desolvation unit. Calibration of the system was performed with frozen multielement standard solutions along a special preparation procedure. Detection limits for the tracers Na, Mg (sea salt), Al (mineral dust) and Zn (anthropogenic source) are 0.1-1 microg kg(-1). Best detection limits in the range of 0.001-0.01 microg kg(-1 )were reached for Co, Pb and all rare earth elements. To validate the method, frozen standard reference materials were measured. The recovery is about +/-10%. Greenland ice core samples from different ages were analysed with the new technique. The results obtained by laser ablation were compared with values from solution analysis, available published data and the particle content. Most elements have shown good correlation with the particle content in the Greenland samples; however, differences could be seen between the values obtained by laser ablation and solution bulk analysis after a tri-acid digestion. The influence of particles is discussed. The high spatially resolved 2D mapping of element concentrations shows strong inhomogeneities along the core axis most probably due to seasonal variations of element deposition.

Initial and long-term results with the CrossFlex stent--data from a national registry

The Cordis CrossFlex trade mark stent is a balloon expandable helical coil made of stainless steel. OBJECTIVE: To assess the short- and long-term safety and efficacy of this stent by conducting a multi-center national registry. METHODS: One hundred and sixteen stents were implanted in 109 patients (mean age 59 3 10 years, 95 males). The lesions were classified as type B2 or C in 56 patients (51%). Successful deployment was achieved in 103 patients (94.5%). Failure was due to damage to the stent (two patients) or inability to reach the lesion (four patients). High-pressure deployment (>14 atm) was used in 68% of cases. RESULTS: Edge dissections occurred in nine patients after high-pressure deployment and necessitated implantation of a second stent. One patient with a large acute myocardial infarction died during hospitalization. Side branch occlusion occurred in five patients (4.6%). Subacute thrombosis occurred in two patients (1.8%) during the first four weeks. During a six-month follow-up period, 18 patients (16.5%) were rehospitalized with recurrent angina. Fifteen patients had coronary angiography and 13 (12.1%) needed additional target lesion revascularization (TLR). Twelve patients required a second PTCA for in-stent restenosis, and one needed a coronary artery bypass graft operation. CONCLUSIONS: The CrossFlex coronary stent can successfully be used in complex coronary lesions, with few short-term complications and a low TLR rate. Operators should be aware of the possibility of edge dissection during high-pressure implantation.

Interleukin-2 receptor concentrations in pregnant women with a history of recurrent miscarriage

BACKGROUND

The mechanism by which the maternal immune system tolerates the fetus during pregnancy is unclear.

METHODS

This study measured interleukin-2 receptor (IL-2R) concentrations in the serum of non-pregnant women (Group 1); healthy first trimester pregnant women (Group 2); pregnant women with a history of recurrent miscarriage whose pregnancies again failed later in the first trimester (Group 3); and first trimester pregnant women with a history of recurrent miscarriage but whose pregnancies on this occasion went successfully to term (Group 4). An initial sample was obtained from all women in Groups 1, 2, 3 and 4. A further sample was obtained 4 weeks later from women in Groups 1, 2 and 4.

RESULTS

The initial sample showed no significant difference in IL-2R concentrations between Groups 1 and 2. Concentrations were significantly higher in Groups 3 (667 +/- 244 U/ml; P < 0.003) and 4 (730 +/- 360 U/ml; P < 0.05) compared with healthy pregnant women (425 +/- 94). When the second sample was obtained concentrations in Group 4 were found to have fallen so that they no longer differed from Group 2.

CONCLUSIONS

Our results confirm earlier findings that a successful pregnancy is associated with significantly lower concentrations of IL-2R.

Phenotyping cytochromes P450 with monoclonal antibodies

Monoclonal antibodies (MAbs) to cytochrome P-450 isozymes can be used to phenotype tissues for epitope-specific cytochrome P-450 content. MAbs that inhibit specific cytochrome P-450 dependent drug or carcinogen reactions are useful tools for quantitative measurement of the individual or classes of cytochromes P-450 that catalyze these reactions. This method has been applied successfully to animal as well as human tissues. Radioimmunoassays based on MAbs have been developed and provide a rapid and efficient means for detecting cytochromes P-450 independent of functional enzyme activity. In addition, MAbs coupled to a Sepharose support can be used to immunopurify cytochromes P-450 in a procedure that is more rapid and efficient than conventional purification schemes. MAbs add a new dimension to analyses of cytochrome P-450 multiplicity and will find numerous applications in elucidation of the relationship between cytochrome P-450 phenotype and carcinogen or drug metabolism.

Focal arterial transgene expression after local gene delivery

BACKGROUND

Gene therapy for the treatment of vascular disease is limited by a low transfection efficiency and/or undesired biological responses.

OBJECTIVE

To determine the transfection efficiency of delivering a liposome/DNA complex into balloon-injured rabbit arteries systematically or using a local delivery catheter.

METHODS

The cationic liposomes N-[1-(2,3-dioleoyloxy) propyl]-N,N,N-trimethylammonium methyl-sulphate and dioleoyl-phosphatidylethanolamine were mixed 1:1 (wt/wt) and combined with the plasmid pCMV-AP containing the human placental alkaline phosphatase (AP) reporter gene. Before initiating the in vivo experiments, the optimal ratio of liposome to DNA complex and the persistence of transgene expression were determined in cultured vascular smooth muscle cells (SMC). In vivo, a Dispatch catheter was used for local delivery of the liposome/DNA complex into rabbit iliac arteries that had been balloon injured five days previously. The contralateral iliac or renal artery was also balloon injured, and liposomes with normal saline were delivered as a negative control. For the systemic delivery group, the liposome/DNA complex was delivered through an ear vein.

RESULTS

AP expression in transfected SMC persisted for 28 days in vitro, although the percentage of transfected cells declined with time (eg, at 24 h it was 27.3%+/-2.9%, at 28 days it was 0.4%+/-0.1%). SMC proliferation in vitro enhanced the transfection efficiency 12-fold. In vivo, local delivery resulted in low levels of transfection in arteries harvested one day postdelivery; however, six of seven arteries harvested three days postdelivery had multiple regions of focal transgene expression involving all three arterial layers. For the systemic delivery group, two of nine arteries expressed the transgene. No transgene expression was found in uninjured arteries in either the local or systemic delivery groups. However, with both local and systemic delivery, balloon-injured arteries that received liposomes and saline showed low levels of AP expression in either the neointima, media or adventitia, presumably due to systemic recirculation of the liposome/AP construct.

CONCLUSIONS

Liposome-mediated gene transfection can be successfully performed to all vessel layers in vivo by using a local delivery catheter, and may provide a therapeutic opportunity for modulating atherosclerosis and restenosis. Unwanted transfection at a distance may occur with catheter-based local delivery and requires further refinement.

Laser ablation inductively coupled plasma mass spectrometry: a new tool for trace element analysis in ice cores

A new method for the detection of trace elements in polar ice cores using laser ablation with subsequent inductively coupled plasma mass spectrometry analysis is described. To enable direct analysis of frozen ice samples a special laser ablation chamber was constructed. Direct analysis reduces the risk of contamination. The defined removal of material from the ice surface by means of a laser beam leads to higher spatial resolution (300-1000 microm) in comparison to investigations with molten ice samples. This is helpful for the detection of element signatures in annual layers of ice cores. The method was applied to the successful determination of traces for the elements Mg, Al, Fe, Zn, Cd, Pb, some rare-earth elements (REE) and minor constituents such as Ca and Na in ice cores. These selected elements serve as tracer elements for certain sources and their element signatures detected in polar ice cores can give hints to climate changes in the past. We report results from measurements of frozen ice samples, the achievable signal intensities, standard deviations and calibration graphs as well as the first signal progression of 205Pb in an 8,000-year-old ice core sample from Greenland. In addition, the first picture of a crater on an ice surface burnt by an IR laser made by cryogenic scanning electron microscopy is presented.

Translesion DNA Synthesis Catalyzed by Human Pol η and Pol κ across 1,N 6-Ethenodeoxyadenosine

1,N(6)-Ethenodeoxyadenosine, a DNA adduct generated by exogenous and endogenous sources, severely blocks DNA synthesis and induces miscoding events in human cells. To probe the mechanism for in vivo translesion DNA synthesis across this adduct, in vitro primer extension studies were conducted using newly identified human DNA polymerases (pol) eta and kappa, which have been shown to catalyze translesion DNA synthesis past several DNA lesions. Steady-state kinetic analyses and analysis of translesion products have revealed that the synthesis is >100-fold more efficient with pol eta than with pol kappa and that both error-free and error-prone syntheses are observed with these enzymes. The miscoding events include both base substitution and frameshift mutations. These results suggest that both polymerases, particularly pol eta, may contribute to the translesion DNA synthesis events observed for 1,N(6)-ethenodeoxyadenosine in human cells.

Pathophysiological role of cytokines in congestive heart failure

Heart failure is a complex neurohumoral and inflammatory syndrome. Recent studies have shown that proinflammatory cytokines (interleukin-1, interleukin-2, interleukin-6, interleukin-10, and tumor necrosis factor) are involved in cardiac depression and in the complex syndrome of heart failure. Understanding the involvement of these cytokines may enable us to reverse cardiac depression and heart failure by the use of monoclonal antibodies directed against specific cytokines to block the downhill progression of heart failure.

Parameters of red blood cell aggregation as correlates of the inflammatory state

To identify clinically relevant parameters of red blood cell (RBC) aggregation, we examined correlations of aggregation parameters with C-reactive protein and fibrinogen in unstable angina (UA), acute myocardial infarction (AMI), and bacterial infection (BI). Aggregation parameters were derived from the distribution of RBC population into aggregate sizes (cells per aggregate) and changing of the distribution by flow-derived shear stress. Increased aggregation was observed in the following order: UA, AMI, and BI. The best correlation was obtained by integration of large aggregate fraction as a function of shear stress. To differentiate plasmatic from cellular factors in RBC aggregation, we determined the aggregation in the presence and absence of plasma and formulated a "plasma factor" (PF) ranging from 0 to 1. In AMI the enhanced aggregation was entirely due to PF (PF = 1), whereas in UA and BI it was due to both plasmatic and cellular factors (0 < or = PF < or = 1). It is proposed that clinically relevant parameters of RBC aggregation should express both RBC aggregate size distribution and aggregate resistance to disaggregation and distinguish between plasmatic and cellular factors.

Responses to the major acrolein-derived deoxyguanosine adduct in Escherichia coli

Acrolein, a reactive alpha,beta-unsaturated aldehyde found ubiquitously in the environment and formed endogenously in mammalian cells, reacts with DNA to form an exocyclic DNA adduct, 3H-8-hydroxy-3-(beta-D-2'-deoxyribofuranosyl)-5,6,7,8-tetrahydropyrido[3,2-a]purine-9-one (gamma-OH-PdG). The cellular processing and mutagenic potential of gamma-OH-PdG have been examined, using a site-specific approach in which a single adduct is embedded in double-strand plasmid DNA. Analysis of progeny plasmid reveals that this adduct is excised by nucleotide excision repair. The apparent level of inhibition of DNA synthesis is approximately 70% in Escherichia coli DeltarecA, uvrA. The block to DNA synthesis can be overcome partially by recA-dependent recombination repair. Targeted G --> T transversions were observed at a frequency of 7 x 10(-4)/translesion synthesis. Inactivation of polB, dinB, and umuD,C genes coding for "SOS" DNA polymerases did not affect significantly the efficiency or fidelity of translesion synthesis. In vitro primer extension experiments revealed that the Klenow fragment of polymerase I catalyzes error-prone synthesis, preferentially incorporating dAMP and dGMP opposite gamma-OH-PdG. We conclude from this study that DNA polymerase III catalyzes translesion synthesis across gamma-OH-PdG in an error-free manner. Nucleotide excision repair, recombination repair, and highly accurate translesion synthesis combine to protect E. coli from the potential genotoxicity of this DNA adduct.

Breaking away from grounded identity? Women academics on the Web

The World Wide Web has provided a new way for academics to find out about others' work and to present versions of their identity. In previous discussions we analyzed how people present themselves in this new medium, in terms of Goffman's ideas of the presentation of self, and commented on gender differences and how issues of credibility and authority are handled by women academics in their homepages. This paper reports discussions with women academics about how they have responded to this opportunity, both in how they present themselves in their own pages, and how they deal with the problems involved in presenting an individual identity within an institutional Web page framework. In presenting themselves in personal homepages, many women academics feel a need to establish their credentials and entitlement to an academic identity. However, the vulnerability of themselves as women remains part of their persona as academics. For example, they were ambivalent about the use of a self-photo on their homepages (most wanted to avoid it, but found it friendly and validating on other women's pages). The discussion considers how far new technology provides opportunities for new forms of identity, or how far the identity presented on the Web is still grounded in people's physical and institutional existence. Women academics feel that the Web has given them new freedom and reduces some traditional gender and status differences (as has been found with other aspects of electronic communication), but they are still wary of it being "yet another way of carrying on the same old gender plot."

Endoglin is overexpressed after arterial injury and is required for transforming growth factor-beta-induced inhibition of smooth muscle cell migration

Endoglin is a homodimeric membrane glycoprotein primarily expressed on endothelial cells. In association with transforming growth factor (TGF)-ss receptors I and II, it can bind TGF-beta1 and -beta3 and form a functional receptor complex. There is increasing evidence that endoglin can modulate the cellular response to TGF-beta, a factor implicated in vascular lesion formation in human and experimental models. The purpose of this study was to analyze the expression of endoglin in normal and balloon-injured porcine coronary arteries and in normal and atherosclerotic human coronary arteries and to determine its ability to mediate the effects of TGF-beta on the migration of vascular smooth muscle cells (SMCs). In normal porcine coronary arteries, endoglin was of low abundance and was found primarily on endothelial cells and adventitial fibroblasts, as well as on a minority of medial SMCs. On days 3, 7, and 14 after angioplasty, endoglin was present not only on endothelial cells but also on adventitial myofibroblasts and medial SMCs of porcine coronary arteries. By day 28, few or no cells expressed endoglin. In situ hybridization revealed that endoglin mRNA expression appeared to be highest in endothelial cells on days 3, 7, and 14 days after injury and absent thereafter. With a second balloon injury, a similar pattern of endoglin protein and mRNA expression was observed. In human vascular tissue, endoglin immunolabeling was higher in endarterectomy specimens removed from diseased coronary arteries than in normal internal mammary arteries. In vitro, antisense oligonucleotides to endoglin decreased its expression and antagonized the TGF-beta-mediated inhibition of human and porcine SMC migration. In summary, upregulation of endoglin occurs during arterial repair and in established atherosclerotic plaques and may be required for modulation of SMC migration by TGF-beta.