Target specificity of insertion element IS30

The Escherichia coli resident mobile element IS30 has pronounced target specificity. Upon transposition, the element frequently inserts exactly into the same position of a preferred target sequence. Insertion sites in phages, plasmids and in the genome of E. coli are characterized by an exceptionally long palindromic consensus sequence that provides strong specificity for IS30 insertions, despite a relatively high level of degeneracy. This 24-bp-long region alone determines the attractiveness of the target DNA and the exact position of IS30 insertion. The divergence of a target site from the consensus and the occurrence of 'non-permitted' bases in certain positions influence the target activity. Differences in attractiveness are emphasized if two targets are present in the same replicon, as was demonstrated by quantitative analysis. In a system of competitive targets, the oligonucleotide sequence representing the consensus of genomic IS30 insertion sites proved to be the most efficient target. Having compared the known insertion sites, we suppose that IS30-like target specificity, which may represent an alternative strategy in target selection among mobile elements, is characteristic of the insertion sequences IS3, IS6 and IS21, too.

Sequence-specific DNA recognition by the myb-like domain of the human telomere binding protein TRF1: a model for the protein-DNA complex

Telomeres consist of tandem arrays of short G-rich sequence motifs packaged by specific DNA binding proteins. In humans the double-stranded telomeric TTAGGG repeats are specifically bound by TRF1 and TRF2. Although telomere binding proteins from evolutionarily distant species are not sequence homologues, they share a Myb-like DNA binding motif. Here we have used gel retardation, primer extension and DNase I footprinting analyses to define the binding site of the isolated Myb-like domain of TRF1 and present a three-dimensional model for its interaction with human telomeric DNA. Our results suggest that the Myb-like domain of TRF1 recognizes a binding site centred on the sequence GGGTTA and that its DNA binding mode is similar to that of the homeodomain-like motifs of the yeast telomere binding protein RAP1. The implications of these findings for recognition of telomeric DNA in general are discussed.

Rapid activation of the complement system by cuprophane depends on complement component C4

Hemodialysis with cuprophane dialyzer membranes promotes rapid activation of the complement system, which is thought to be mediated by the alternative pathway. Complete hereditary deficiency of complement C4, a classical pathway component, in two hemodialysis patients provided the opportunity to investigate a possible role of the classical pathway. In two hemodialysis patients with both C4 isotypes, C4A and C4B, and in one patient with C4B deficiency complement activation occurred immediately after the onset of hemodialysis, with peak levels of C3a and terminal complement complex (TCC) after ten to fifteen minutes. In patients with complete C4 deficiency, C3a and TCC remained unchanged for fifteen minutes and increased thereafter, reaching the highest level after thirty minutes. The leukocyte nadir was also delayed from fifteen to thirty minutes. In vitro incubation of normal, C4A- or C4B-deficient serum with cuprophane caused complement activation after fifteen minutes. In contrast, no activation was observed in sera of four C4-deficient patients. The addition of normal serum or purified human C4 restored the capacity for rapid complement activation. In one patient with severe immunoglobulin deficiency, C3a and TCC levels increased only moderately after 25 minutes of cuprophane dialysis. This patient's serum also exhibited delayed complement activation in vitro, which was normalized after pretreatment of cuprophane with immunoglobulins. Preincubation of normal serum with MgEGTA, a blocker of the classical pathway, inhibited rapid complement activation through cuprophane. As basal levels of C4a are markedly increased in hemodialysis patients (3450 +/- 850 ng/ml) compared to healthy controls (224 +/- 81 ng/ml), no further elevation of C4a was detectable during cuprophane hemodialysis. Incubation of normal serum with cuprophane, however, caused a slight increase in C4a after five minutes. These results indicate that the initial deposition of complement C3b on the cuprophane membrane, necessary for activation of the amplification loop of the alternative pathway, is mediated by the classical pathway C3-convertase C4b2a. We propose an extended concept of complement activation through cuprophane, which is based on four steps: (a) binding of anti-polysaccharide antibodies, (b) classical pathway activation, (c) alternative pathway activation and (d) terminal pathway activation.

A placebo-controlled, double-blind trial of the long-term effects of albuterol administration in patients with cystic fibrosis

This placebo-controlled study was designed to confirm a previously performed open label study that showed significant improvement in spirometry on maintenance therapy with albuterol for 1 year. In a double-blind, cross-over trial, albuterol (by metered dose inhaler) 180 microg b.i.d. or placebo were given for 6 months each. Spirometry was monitored at the start, and 3 and 6 months following initiation of each arm of the study. Peak expiratory flow rate (PEFR) was measured twice daily at home before and after study drug administration. Only patients with clinically detectable lung disease were enrolled. Twenty-one patients finished the study. All spirometric tests showed a significant improvement from start to end of the 6 month treatment with albuterol; there was no significant change on placebo. Forced vital capacity improved by 8.2% and forced expiratory volume in 1 s by 12.1% on albuterol therapy. Nevertheless, there was no significant difference between change on albuterol and change on placebo. Home measurements of PEFR showed a significant improvement of 4.7% on albuterol and a non-significant change of 2.0% on placebo from the first to the last week of treatment. None of the long-term improvements (spirometry or home PEFR) correlated with mean daily bronchodilation. For albuterol, the number of days of hospitalization was less than half that for patients on placebo (1.0/patient on albuterol versus 2.6 on placebo), but this did not reach statistical significance. These results suggest a beneficial effect from maintenance therapy with albuterol. Bronchodilation alone probably cannot explain the long-term benefits of albuterol, and other mechanisms may play a role. The lack of significant difference between change on albuterol and change on placebo is probably due to too small a number of patients in this study and lack of statistical power.

Increased plasma concentrations of LDL-unbound apo(a) in patients with end-stage renal disease

Lipoprotein(a) [Lp(a)] and its characteristic glycoprotein apolipoprotein(a) [apo(a)] are risk factors for atherosclerosis in the general population. Patients with renal disease show an elevation of Lp(a). Recent studies have described an arteriovenous difference of Lp(a) in the renovascular bed as well as the plasma-derived fragmented LDL-unbound apo(a) in urine, suggesting that the kidney is involved in the metabolism of Lp(a). We therefore investigated whether patients with chronic renal failure have higher levels of LDL-unbound apo(a) and whether this could account for the increased Lp(a) concentrations in these patients. In addition, we studied the possible generation of apo(a) fragments in vitro by mimicking uremic plasma conditions and by investigating the assembly of Lp(a) in cell culture experiments. Patients treated by hemodialysis (N = 185) and by continuous ambulatory peritoneal dialysis (CAPD; N = 20) had markedly elevated absolute (1.22 +/- 1.55 mg/dl and 2.14 +/- 2.86 mg/dl) as well as relative (7.5% and 7.3%) amounts of LDL-unbound apo(a) in comparison to controls (0.46 +/- 0.48 mg/dl or 4.5%). Following renal transplantation the absolute amount decreased significantly. Lp(a) plasma concentration was the most important determining variable for the absolute amount of LDL-unbound apo(a) and showed a positive correlation in both hemodialysis patients (r = 0.85) and controls (r = 0.92). In vitro experiments demonstrated that "uremization" of plasma samples did not generate a higher amount of LDL-unbound apo(a). Although LDL of renal patients has different chemical and structural properties as compared to control LDL, the extracellular assembly of Lp(a) did not differ between patients and controls. Therefore, the higher amounts of LDL-unbound apo(a) found in renal disease are not caused by an impaired assembly of Lp(a), but rather indicate a catabolic role of the kidney for LDL-unbound apo(a) as was already shown for Lp(a). Despite a small contribution, these elevated levels cannot explain the higher Lp(a) values found in patients with end-stage renal disease.

Synchronization of oscillatory responses in visual cortex correlates with perception in interocular rivalry

In subjects suffering from early onset strabismus, signals conveyed by the two eyes are not perceived simultaneously but in alternation. We exploited this phenomenon of interocular suppression to investigate the neuronal correlate of binocular rivalry in primary visual cortex of awake strabismic cats. Monocularly presented stimuli that were readily perceived by the animal evoked synchronized discharges with an oscillatory patterning in the gamma-frequency range. Upon dichoptic stimulation, neurons responding to the stimulus that continued to be perceived increased the synchronicity and the regularity of their oscillatory patterning while the reverse was true for neurons responding to the stimulus that was no longer perceived. These differential changes were not associated with modifications of discharge rate, suggesting that at early stages of visual processing the degree of synchronicity rather than the amplitude of responses determines which signals are perceived and control behavioral responses.

LDL-unbound apolipoprotein(a) and carotid atherosclerosis in hemodialysis patients

High lipoprotein(a) [Lp(a)] plasma concentrations, which are genetically determined by apo(a) size polymorphism, are directly associated with an increased risk for atherosclerosis. Patients with end-stage renal disease (ESRD), who show an enormous prevalence of cardiovascular disease, have elevated plasma concentrations of Lp(a). In recent studies we were able to show that apo(a) size polymorphism is a better predictor for carotid atherosclerosis and coronary artery disease in hemodialysis patients than concentrations of Lp(a) and other lipoproteins. Less than 5% of apo(a) in plasma exists in a low-density lipoprotein (LDL)-unbound form. This "free" apo(a) consists mainly of disintegrated apo(a) molecules of different molecular weight, ranging from about 125 to 360 kDa. LDL-unbound apo(a) molecules are elevated in patients with ESRD. The aim of this study was therefore to investigate whether the LDL-unbound form of apo(a) contributes to the prediction of carotid atherosclerosis in a group of 153 hemodialysis patients. The absolute amount of LDL-unbound apo(a) showed a trend to increasing values with the degree of carotid atherosclerosis, but the correlation of Lp(a) plasma concentrations with atherosclerosis was more pronounced. In multivariate analysis the two variables were related to neither the presence nor the degree of atherosclerosis. Instead, the apo(a) phenotype took the place of Lp(a) and LDL-unbound apo(a). After adjustment for other variables, the odds ratio for carotid atherosclerosis in patients with a low molecular weight apo(a) phenotype was about 5 (p<0.01). This indicates a strong association between the apo(a) phenotype and the prevalence of carotid atherosclerosis. Finally, multivariate regression analysis revealed age, angina pectoris and the apo(a) phenotype as the only significant predictors of the degree of atherosclerosis in these patients. In summary, it seems that LDL-unbound apo(a) levels do not contribute to the prediction of carotid atherosclerosis in hemodialysis patients. However, this does not mean that "free", mainly disintegrated, apo(a) has no atherogenic potential.

Evidence for benefits of early intervention with non-steroidal drugs in asthma

Earlier guidelines recommended the use of bronchodilators, such as beta 2-agonists, in patients with mild asthma (defined as having symptoms present on < or = 3 days per week), the use of sodium cromoglycate in moderately severe asthma patients (symptoms present on > 3 days per week), and inhaled corticosteroids in those not satisfactorily controlled by sodium cromoglycate (severe asthma). A retrospective study was performed to evaluate the effect of such a stepwise approach on the long-term outcome of the disease. A group of 175 children were followed for a mean of 8.4 years (range, 2-16 years) and divided into mild (treated with "as-needed" bronchodilators, usually beta 2-agonists), moderate (treated with sodium cromoglycate), and severe asthmatics (treated with inhaled corticosteroids). Treatment was altered if patients deteriorated or improved. The clinical improvement (as determined by days with symptoms present, emergency room visits, and hospitalizations) of patients being treated with anti-inflammatory agents (sodium cromoglycate or inhaled corticosteroids) was significantly greater than for those receiving bronchodilators. Delay in starting sodium cromoglycate, but not inhaled corticosteroids, had a negative effect on both clinical outcome and pulmonary function. Spirometry showed a significant worsening in the mild group but improvements in the moderate and severe groups. Thus, treatment with anti-inflammatory drugs improves the long-term prognosis and at least partially reverses the natural history of the disease; however, sodium cromoglycate should be started in milder patients than those recommended by the earlier guidelines. The new Global Initiative guidelines have recommended moving the indication for the start of non-steroidal anti-inflammatory drugs from having symptoms on > 3 days per week to having symptoms on > 1 day per week. Considering the fact that inhaled corticosteroids have some side effect even at standard doses, especially in patients with milder asthma, it would appear that a stepwise approach, starting with non-steroidal anti-inflammatory drugs is the most appropriate therapy for patients with mild-to-moderate asthma.

Renovascular arteriovenous differences in Lp[a] plasma concentrations suggest removal of Lp[a] from the renal circulation

High plasma concentrations of lipoprotein[a] (Lp[a]) are considered a genetically determined risk factor for atherosclerosis. Lp[a] is produced by the liver. The site(s) and mechanism(s) of catabolism are presently unclear. Lp[a] is elevated secondary to end-stage renal disease which suggests a direct or indirect role of the kidney in the metabolism of Lp[a]. We therefore investigated, by a simple in vivo approach, whether Lp[a] is removed by the human kidney. Lp[a] plasma concentrations were measured simultaneously by various methods in the ascending aorta and renal vein of 100 patients undergoing coronary angiography or coronary angioplasty. Lp[a] levels differed significantly between the two vessels even after correcting for hemoconcentration (20.1 +/- 21.6 mg/dL versus 18.7 +/- 20.3 mg/dL, P < 0.001). This corresponds to a mean arteriovenous difference of -1.4 mg/ dL or -9% of the arterial concentration. No Lp[a] or intact apo[a] could be detected in urine from healthy probands. Although we cannot assign the kidney a regulatory role for Lp[a] plasma levels in humans with normal renal function, we conclude from our data that substantial amounts of this atherogenic lipoprotein are taken up by the kidney. The underlying mechanisms are unknown at the moment. This study therefore demonstrates for the first time that the human kidney plays an active role in the catabolism of Lp[a]. This may explain the elevated Lp[a] concentrations found in patients with chronic renal insufficiency.

Soluble intercellular adhesion molecule-1 (ICAM-1) in serum and urine: correlation with renal expression of ICAM-1 in patients with kidney disease

A soluble form of intercellular adhesion molecule-1 (sICAM-1) has been described in serum and other body fluids. In order to determine whether sICAM-1 in serum and urine is a useful marker of inflammatory activity in kidney diseases we measured sICAM-1 in serum and urine of fifty patients who underwent renal biopsy, and of twenty healthy individuals. Expression of ICAM-1 on proximal tubular epithelial cells was investigated by immunohistochemistry. Soluble ICAM-1 in serum did not differ between patients and controls (354 +/- 129 ng/ml vs. 305 +/- 52 ng/ml). By multiple regression analysis sICAM-1 correlated with tubular expression of ICAM-1 (p < 0.01), but not with serum creatinine, infiltrating leukocytes, urinary ICAM-1 or proteinuria. In healthy controls mean urinary ICAM-1/cr was 2.5 +/- 3.0 ng/mg creatinine and differed significantly from that of patients (14.5 +/- 14.9 ng/mg) (p < 0.005). Patients with minimal-change disease had the highest uICAM-1 levels. The ratio of urinary ICAM-1 and proteinuria was remarkably constant in all patients with 6.0 +/- 0.9 ng/mg. By multiple regression analysis uICAM-1/cr correlated with proteinuria/cr (p < 0.001) and sICAM-1 (p < 0.005). These data show that sICAM-1 does to some degree reflect ICAM-1 expression in the kidney, whereas uICAM-1 is derived from glomerular filtration and closely parallels proteinuria. Both sICAM-1 and uICAM-1 are not useful to estimate ICAM-1 expression and inflammatory activity in the kidney.

Divergent effects of hemodialysis and continuous ambulatory peritoneal dialysis on cardiac diastolic function

OBJECTIVE

To investigate the effects of dialysis procedures on cardiac diastolic function.

DESIGN

Comparative, nonrandomized matched pair study.

SETTING

Nephrology and cardiology departments at a university hospital.

PATIENTS

Thirty-four patients on hemodialysis (HD) (n = 17) and continuous ambulatory peritoneal dialysis (CAPD) (n = 17), matched by sex, age, duration of dialysis treatment, and presence/absence of diabetes.

MEASUREMENTS

Cardiac function was estimated by means of M-mode, two-dimensional, and spectral Doppler echocardiography, and results were statistically evaluated by means of univariate and multivariate analytical procedures.

RESULTS

Although not statistically significant, trends towards differences between the two patient groups were detected for left ventricular mass (p = 0.083) and parameters of diastolic function (p = 0.079). These differences in left ventricular performance and diastolic function between HD and CAPD patients were also evident when calculating Spearman rank correlation coefficients. Left ventricular mass and diastolic function were closely correlated to each other in all dialysis patients. Moreover, by means of a multivariate analytical procedure (Hotelling T-square test), diversities in diastolic function between the two patient groups could be clearly established (p = 0.037), with more impaired diastolic function in HD patients. In addition, cardiac performance was shown to depend to a certain extent on hemoglobin concentration.

CONCLUSION

Clear differences in diastolic function and cardiac performance were evident between CAPD and HD patients. From the data of our pilot study, it may be speculated whether decrease of left ventricular mass could be beneficial for the improvement of diastolic function and cardiac hemodynamics in dialysis patients.

Metabolic effects of i.v. propacetamol, metamizol or external cooling in critically ill febrile sedated patients

We have measured the metabolic response to sequential administration of propacetamol, metamizol and/or external cooling in 20 febrile patients under sedation and analgesia and during mechanical ventilation. There was no change in temperature (T degree) after propacetamol therapy, whereas after metamizol only a small decrease was noted (from 38.9 (SEM 0.2) to 38.5 (0.3) degrees C; P = 0.02). External cooling produced a significant decrease in T degree (39.1 (0.2) to 37.1 (0.2) degrees C; P < 0.0001) accompanied by a decrease in energy expenditure (EE) (2034 (73) to 1791 (88) kcal day-1; P < 0.004). Heart rate and minute ventilation decreased significantly in parallel. There were no other changes in haemodynamics or pulmonary gas exchanges. We conclude that propacetamol and metamizol did not produce a clinically significant decrease in T degree in febrile ICU patients whereas external cooling decreased both T degree and EE. The parallel decrease in body temperature and EE seemed to be related to opioid administration or sedation, or both.

Recognition of telomeric DNA

The three-dimensional structure of the yeast telomere-binding protein RAP1 in complex with DNA provides the first insight into telomeric DNA recognition. RAP1 binds to DNA via two Myb/homeodomain-like motifs, which are DNA-binding folds previously identified in transcription factors. This, together with the finding that human TRF1 and other telomere-binding factors contain Myb-like motifs, has led us to speculate that a conserved protein fold might be used for telomeric DNA recognition.

Visuomotor integration is associated with zero time-lag synchronization among cortical areas

Information processing in the cerebral cortex invariably involves the activation of millions of neurons that are widely distributed over its various areas. These distributed activity patterns need to be integrated into coherent representational states. A candidate mechanism for the integration and coordination of neuronal activity between different brain regions is synchronization on a fine temporal scale. In the visual cortex, synchronization occurs selectively between the responses of neurons that represent related features and that need to be integrated for the generation of coherent percepts; neurons in other areas of the cerebral cortex also synchronize their discharges. However, little is known about the patterns and the behavioural correlates of synchrony among widely separated cortical regions. Here we report that synchronization occurs between areas of the visual and parietal cortex, and between areas of the parietal and motor cortex, in the awake cat. When cats responded to a sudden change of a visual pattern, neuronal activity in cortical areas exhibited synchrony without time lags; this synchrony was particularly strong between areas subserving related functions. During reward and inter-trial episodes, zero-time-lag synchrony was lost and replaced by interactions exhibiting large and unsystematic time lags.

Spatiotemporal distribution of intracellular calcium transients during epileptiform activity in guinea pig hippocampal slices

Calcium ions are known to play an important role in epileptogenesis. Although there is clear evidence for increased neuronal calcium influx during epileptiform potentials, direct measurements of the corresponding intracellular calcium transients are rare and the origin of calcium influx is not known. Therefore the spatial and temporal distribution of intracellular calcium transients during epileptiform activity in guinea pig hippocampal slices was monitored with the use of the indicator Calcium-Green and a fast optical recording method. Two models of epilepsy (bicuculline and low Mg2+) were compared. In both models, single epileptiform events were evoked by electrical stimulation of the Schaffer collaterals in CA1 or of stratum pyramidale in area CA3. Intracellular calcium transients during epileptiform activity were approximately 5 times larger than during control stimulation. Calcium transients during epileptiform activity were present across at least the entire CA1 area, whereas presynaptic calcium transients from stimulated fibers were only seen at a distance up to 1 mm from the stimulation site. DL-2-amino-5-phosphonovaleric acid (APV), a specific antagonist of the N-methyl-D-aspartate (NMDA) receptor, abolished low-Mg2+ epileptiform activity and reduced bicuculline-induced epileptiform activity; it reduced calcium transients following stimulation of CA1 by only 29% (bicuculline) and 38% (low Mg2+). For comparison, calcium transients during control stimulation were 78% (bicuculline) and 69% (low Mg2+) smaller than epileptiform calcium transients. At a distance from the stimulation site, calcium transients and their NMDA-receptor-dependent components were largest in stratum pyramidale in the bicuculline model and in stratum oriens in the low-Mg2+ model. In both models, minimal onset latencies of calcium influx shifted with increasing distance to the stimulation electrode from stratum radiatum to stratum oriens. APV reduced the extent of spread of calcium transients in the low-Mg2+ model. In the bicuculline model, the spatial extent of spread of epileptiform calcium transients was not affected by application of APV; however, the mean velocity of spread was reduced from 0.20 to 0.12 m/s. In conclusion, the large size of calcium transients and of their NMDA-receptor-dependent components in stratum pyramidale or stratum oriens as well as shortest onset latencies of calcium transients at these sites suggest an important role of cell somata, basal dendrites, and possibly local circuit excitatory interactions for the generation and spread of epileptiform activity.

The effect of drug therapy on long-term outcome of childhood asthma: a possible preview of the international guidelines

BACKGROUND

International guidelines classify childhood asthma as mild, moderate, and severe and recommend treatment with "as needed" bronchodilators, cromolyn sodium, and inhaled corticosteroids, respectively. Recently, some investigators proposed inhaled corticosteroids as first-line therapy to avoid possible irreversible airway obstruction. This article describes a retrospective study assessing the effect of the guidelines' approach on the long-term outcome of childhood asthma and the possible effect of delaying initiation of administration of corticosteroids.

METHODS

A retrospective review was performed on the charts of 175 children, and an end-of-study questionnaire plus results of spirometry completed the data. The mean age at start of study was 6.5 years, and the children were followed up for 2.2 to 16.8 years (mean, 8.4 years). Treatments included bronchodilators as needed only (patients with mild asthma), cromolyn sodium (patients with moderate asthma), and inhaled corticosteroids (patients with severe asthma).

RESULTS

Frequency of symptoms, unscheduled doctors' visits, emergency department visits, hospitalizations, and missed school days decreased for the whole group. Statistically significant between-treatment differences favored both antiinflammatory therapies over as-needed bronchodilator treatment (cromolyn sodium: symptoms, p < 0.05; hospitalizations, p < 0.05; corticosteroids: emergency department visits, p < 0.05; hospitalizations, p < 0.05). Mean spirometry results improved, and the postbronchodilator values approached normal by study end. Assessed by treatment, spirometry decreased with bronchodilators but improved in patients treated with cromolyn sodium or inhaled corticosteroids. Delay in starting administration of cromolyn sodium had an unfavorable effect on clinical outcomes (p < 0.01) and spirometry (p < 0.05); delay in starting administration of corticosteroids did not.

CONCLUSIONS

Treatment with antiinflammatory drugs (cromolyn sodium or inhaled corticosteroids), but not as-needed bronchodilators alone, improves the long-term prognosis of asthma. It is possible that starting administration of nonsteroid antiinflammatory agents earlier than the present recommendations could further improve clinical outcomes, but prospective studies are needed.

Clinical effects of nedocromil sodium on challenges invoking neuronal mechanisms and on virally induced symptoms

Although sensory nerve activity may be important to the human airway in numerous possible ways, the relevance of "neurogenic inflammation" to the onset and development of asthma is unknown. However, several of the symptoms of asthma (bronchoconstriction, cough, and dyspnea) have a neuronal component that can be modeled in the laboratory by various stimuli that are thought to invoke sensory nerve activation. Nedocromil sodium is highly effective against bronchoconstriction induced by bradykinin, the tachykinins substance P and neurokinin A, and sulfur dioxide and metabisulfite. The results for induced cough in healthy subjects are equivocal, although the drug is effective on spontaneously occurring cough in patients with asthma. Nedocromil sodium had a modest but significant effect on symptoms associated with episodes of viral infection.