Superantigen expression is driven by both mouse mammary tumor virus long terminal repeat-associated promoters in transgenic mice

In addition to the usual retroviral promoter, the mouse mammary tumor virus (MMTV) long terminal repeat carries a second promoter located in the U3 region. Here we show that both of these promoters are independently able to give rise to superantigen activity in transgenic mice. The ability of multiple MMTV promoters to drive superantigen expression underscores its importance in the virus life cycle.

Assessment of middle cerebral artery diameter after aneurysmal subarachnoid hemorrhage by transcranial color-coded duplex sonography

This study examined if vasospasm after aneurysmal subarachnoid hemorrhage could be visualized by middle cerebral artery (MCA) diameter changes in transcranial color-coded duplex sonography (TCCS). Comparative measurements between mean blood velocity (MBV) and MCA diameter were carried out in 17 patients in 76 instances. At two depth ranges (proximal, 60 55 mm: distal, 50-45 mm) two observers assessed the MCA diameter as indicated by the visualized blood flow column. At both points of measurement, the diameter differences between the two observers were within the ¿ 2 S.D. range of the mean difference indicating interobserver agreement. In 17 instances, MBV was > 120 cm/s indicating vasospasm but MBV did not correlate with absolute or relative diameter changes. MCA diameter assessment in TCCS seems reproducible. Because TCCS imaging is influenced by several factors comparative angiographic studies are necessary to clarify the TCCS findings.

Target site concentrations after continuous infusion and bolus injection of cefpirome to healthy volunteers

BACKGROUND

Recent data indicate a higher level of effectivity of beta-lactam antibiotics if serum concentrations are kept above the minimal inhibitory concentration (MIC) of the pathogen. This concept would favor continuous infusion over bolus dosing. However, it is usually not the serum concentration but the free interstitial concentration in the target tissue that determines antibiotic activity. We therefore set out to measure effective drug concentrations in the interstitial space of muscle and subcutaneous adipose tissue and to compare trough levels and times above the MIC after bolus versus continuous infusion of cefpirome.

METHODS

Twelve healthy volunteers received a single dose of 2 g cefpirome as an intravenous bolus or as a continuous infusion over 8 hours in a crossover design, and the resulting free interstitial tissue concentrations were measured with use of microdialysis.

RESULTS

After bolus injection, mean interstitial trough concentrations were 3.0 +/- 1.9 microg/mL and 2.1 +/-1.0 microg/mL for muscle and subcutaneous tissue, respectively; continuous infusion resulted in trough levels of 10.1 +/- 6.8 microg/mL and 10.1 +/- 4.6 microg/mL for muscle and subcutaneous tissue, respectively. This resulted in significantly longer times above the MIC with continuous infusion for Staphylococcus epidermidis and Enterobacter cloacae. Bacteria with an MIC < or =1 would be covered by either method, whereas higher doses seem to be necessary for Pseudomonas aeruginosa.

CONCLUSION

Although susceptible organisms will usually be covered sufficiently with standard dosing regimens, soft tissue infections with bacteria that have MIC values of 2 to 8 may profit from continuous application. Coverage of P aeruginosa, however, would be inadequate with conventional daily doses of 4 g cefpirome regardless of the method of application.

Acetyl-CoA synthetase from the amitochondriate eukaryote Giardia lamblia belongs to the newly recognized superfamily of acyl-CoA synthetases (Nucleoside diphosphate-forming)

The gene coding for the acetyl-CoA synthetase (ADP-forming) from the amitochondriate eukaryote Giardia lamblia has been expressed in Escherichia coli. The recombinant enzyme exhibited the same substrate specificity as the native enzyme, utilizing acetyl-CoA and adenine nucleotides as preferred substrates and less efficiently, propionyl- and succinyl-CoA. N- and C-terminal parts of the G. lamblia acetyl-CoA synthetase sequence were found to be homologous to the alpha- and beta-subunits, respectively, of succinyl-CoA synthetase. Sequence analysis of homologous enzymes from various bacteria, archaea, and the eukaryote, Plasmodium falciparum, identified conserved features in their organization, which allowed us to delineate a new superfamily of acyl-CoA synthetases (nucleoside diphosphate-forming) and its signature motifs. The representatives of this new superfamily of thiokinases vary in their domain arrangement, some consisting of separate alpha- and beta-subunits and others comprising fusion proteins in alpha-beta or beta-alpha orientation. The presence of homologs of acetyl-CoA synthetase (ADP-forming) in such human pathogens as G. lamblia, Yersinia pestis, Bordetella pertussis, Pseudomonas aeruginosa, Vibrio cholerae, Salmonella typhi, Porphyromonas gingivalis, and the malaria agent P. falciparum suggests that they might be used as potential drug targets.

Preparation and characterization of 'heparinocytes': erythrocytes with covalently bound low molecular weight heparin

In an attempt to create the possibility of stable, long acting, intravascular anticoagulation, low molecular weight heparin was modified by introducing a sulfhydryl group into the molecule (LMWH-SH). Human erythrocytes were covalently grafted with LMWH-SH by the use of a heterobifunctional coupling reagent which reacts with the SH group of LMWH-SH and surface exposed amino groups of erythrocytes now called 'heparinocytes' (HC). HC were morphologically indistinguishable from untreated erythrocytes and displayed identical osmotic resistance. The functionality of HC was analyzed by classical coagulation tests in which they dose dependently inhibited clot formation. HC were also functional in recalcified whole blood inhibiting thrombin formation as assessed by the cleavage of the chromogenic substrate S-2238. The system appears applicable as a potential autologous, long-term anticoagulant treatment or prophylaxis.

Formation of etheno adducts and their effects on DNA polymerases

Etheno (epsilon) and related DNA adducts are formed from the reaction of certain bifunctional electrophiles with DNA. Our interest has been focused on oxiranes substituted with leaving groups, e.g. 2-chlorooxirane, the epoxide derived from the carcinogen vinyl chloride. The chemical mechanisms of the formation of the major etheno products derived from adenine, cytosine and guanine have been elucidated by nuclear magnetic resonance analysis and 13C-labelled precursors. The amounts of all major etheno adducts have been quantified in DNA treated with 2-chlorooxirane by coupled high-performance liquid chromatography of nucleoside and base products. 1,N2-epsilon-Gua, its formally hydrated but stable hemiaminal HO-ethanoGua (5,6,7,9-tetrahydro-7-hydroxy-9-oxoimidazo[1,2-a]purine) and 1,N2-ethanoGua have all been inserted at a single site in oligonucleotides. All three of these bases block polymerases, cause misincorporations and produce some mutations in bacteria. The patterns of blockage and substitution vary among polymerases. In nucleotide excision repair-deficient Escherichia coli, 1,N2-epsilon-Gua yielded a calculated 16% mutation frequency (base-pair substitutions) when the results were corrected for strand usage. 1,N2-epsilon-Gua was also examined in Chinese hamster ovary cells with a stable integration system; the mutants are more complex than observed in bacteria and include rearrangements, deletions and base-pair substitutions other than at the adduct site.

The Fab-8 boundary defines the distal limit of the bithorax complex iab-7 domain and insulates iab-7 from initiation elements and a PRE in the adjacent iab-8 domain

The Drosophila bithorax complex Abdominal-B (Abd-B) gene specifies parasegmental identity at the posterior end of the fly. The specific pattern of Abd-B expression in each parasegment (PS) determines its identity and, in PS10-13, Abd-B expression is controlled by four parasegment-specific cis-regulatory domains, iab-5 to iab-8, respectively. In order to properly determine parasegmental identity, these four cis-regulatory domains must function autonomously during both the initiation and maintenance phases of BX-C regulation. The studies reported here demonstrate that the (centromere) distal end of iab-7 domain is delimited by the Fab-8 boundary. Initiators that specify PS12 identity are located on the proximal iab-7 side of Fab-8, while initiators that specify PS13 identity are located on the distal side of Fab-8, in iab-8. We use transgene assays to demonstrate that Fab-8 has enhancer blocking activity and that it can insulate reporter constructs from the regulatory action of the iab-7 and iab-8 initiators. We also show that the Fab-8 boundary defines the realm of action of a nearby iab-8 Polycomb Response Element, preventing this element from ectopically silencing the adjacent domain. Finally, we demonstrate that the insulating activity of the Fab-8 boundary in BX-C is absolutely essential for the proper specification of parasegmental identity by the iab-7 and iab-8 cis-regulatory domains. Fab-8 together with the previously identified Fab-7 boundary delimit the first genetically defined higher order domain in a multicellular eukaryote.

Effects of ATP and derivatives on neuropile glial cells of the leech central nervous system

We investigated the effects of ATP (adenosine 5'-triphosphate) and derivatives on leech neuropile glial cells, focusing on exposed glial cells. ATP dose-dependently depolarized or hyperpolarized neuropile glial cells in situ as well as exposed neuropile glial cells. These potential shifts varied among cells and repetitive ATP application did not change their amplitude, duration or direction. In exposed neuropile glial cells, ATP most frequently induced a Na(+)-dependent depolarization and decreased the input resistance. The agonist potency ATP > ADP (adenosine 5'-diphosphate) > AMP (adenosine 5'-monophosphate) > adenosine indicates that P2 purinoceptors mediate this depolarization. The P2Y agonist 2-methylthio-ATP mimicked the ATP-induced depolarization, whereas the P2Y antagonist PPADS (pyridoxal-phosphate-6-azophenyl-2', 4'-disulphonic acid) reduced it. P2X agonists were without effect. Because the P1 antagonist 8-SPT (8-(p-sulphophenyl)-theophylline) also depressed ATP-induced depolarizations and some ATP-insensitive glial cells responded to adenosine, we suggest coexpression of metabotropic P2Y and P1 purinoceptors. The ATP-induced depolarization requires activation of Na(+) channels or nonselective cation channels, whereas the ATP-induced hyperpolarization indicates activation of K(+) channels. ATP also increased the intracellular Ca(2+) concentration ([Ca(2+)](i)), that is independent of Ca(2+) influx but reflects intracellular Ca(2+) release possibly triggered by IP(3) formation. ADP and AMP also increased [Ca(2+)](i), but were less efficient than ATP; adenosine and 2-methylthio-ATP did not affect [Ca(2+)](i). In view of the mobilization of intracellular Ca(2+), ATP is clearly different from other leech neurotransmitters, because it enables intracellular Ca(2+) signaling without causing prominent changes in glial membrane potential. Thus disturbance of the extracellular microenvironment and the demand for metabolic energy are minimized.

Epitope spreading and a varying but not disease-specific GAD65 antibody response in Type I diabetes. The Childhood Diabetes in Finland Study Group

AIMS/HYPOTHESIS

The aim of this study was to analyse the conformational and linear epitope profiles of glutamic acid decarboxylase antibody (GAD65-ab)-positive sera to find disease-specific epitope profiles and to study, whether GAD65-ab epitope recognition changes or spreads during the prediabetic period and, thus, can provide markers to differentiate early from later stages of progression to diabetes.

METHODS

Sera from subjects before (n = 21), at onset (n = 44), or at increased risk of Type I (insulin-dependent) diabetes mellitus (n = 20) and from patients with stiff-man syndrome (SMS, n = 18) or polyendocrine autoimmune syndrome (PAS, n = 21) were analysed for conformational and linear GAD65 epitope recognition by an immunohistochemical blocking test based on human monoclonal GAD65-ab (MICA 1-10) and western blotting of a GAD65 epitope-cDNA-library.

RESULTS

A redundant reactivity of many GAD65-ab positive sera to three major conformational (EP-1, EP-2, EP-3) and two dominant linear epitope clusters (amino acid 1-124 and 535-585) was observed in diabetes, polyendocrine autoimmune syndrome and stiff-man syndrome and no disease-specific epitopes or epitope-profiles were detected. Epitope recognition broadened with higher titres and with the vulnerability of patients to acquire additional autoimmune diseases apart from diabetes. Low GAD65-ab serum titres (< 1200 arbitrary units) and EP-1 recognition in the absence of EP-2 binding characterised the early immune response. Changing epitope profiles combined stable recognition of EP-1 with gain or loss of reactivity to C-terminal epitopes during follow-up.

CONCLUSION/INTERPRETATION

A maturing autoantibody response, which could spread from EP-1-recognition to other regions of GAD65, resulted in titre-related rather than disease-specific epitope profiles which were not sufficient to predict whether GAD65-ab positive subjects will progress to Type I diabetes, autoimmune polyendocrine syndrome or stiff-man syndrome.

Rapid and sensitive detection of enhanced green fluorescent protein expression in paraffin sections by confocal laser scanning microscopy

Various forms of green fluorescent protein (GFP) have become important reporters of gene transfer and expression after transfection or infection of cells in cell culture. Frequently, molecular biological assays (Northern blots, PCR) are applied to detect reporter gene expression in target organs. However, these methods are not suitable for evaluation of tissue- or cell-specific expression which would be of great interest especially in case of using tissue-specific promoters. Therefore, organs of transgenic mice with the enhanced green fluorescent protein (EGFP) gene under control of the cytomegalovirus (CMV) promoter were processed for histology by formaldehyde fixation and embedding in paraffin. Sections were deparaffinized, mounted and evaluated for fluorescence in a confocal laser scanning microscope. This method combines the advantages of direct exploitation of tissue sections without further staining procedures with evaluable tissue-, cell-, and even subcellular-specific distribution patterns of EGFP expression in tissues. Results obtained by direct evaluation of EGFP fluorescence in paraffin sections were confirmed by immunohistochemical staining with anti-EGFP. In the present report, we demonstrate that application of confocal microscopy on routinely processed histological preparations is very suitable for determining gene transfer efficiency and promotor activities.

Pharmacokinetics and pharmacodynamics of the novel H1-receptor antagonist emedastine in healthy volunteers

OBJECTIVE

Emedastine is a novel H1-receptor antagonist with pre-clinically well-documented anti-allergic effects. Here, we set out to study the relationship between emedastine pharmacokinetics and the suppressive effect on histamine-induced wheals and flares, and to compare these effects to placebo and cetirizine.

METHODS

Emedastine (4 mg q.d.), emedastine (2 mg b.i.d.), cetirizine (10 mg q.d.) and placebo were administered to healthy volunteers in a double-blind, cross-over fashion. On day 1 and day 5 (steady state) following drug administration, wheals and flares were induced by skin-prick testing with 1 mg ml(-1) or 10 mg ml(-1) histamine.

RESULTS

Following the administration of 4 mg emedastine q.d., mean area under the concentration-time curve (AUC)0-24 values of 34.49 +/- 24.07 ng h ml(-1) and 47.05 +/- 36.12 ng h ml(-1) were attained on day 1 and day 5, respectively. Following the administration of emedastine (2 mg b.i.d.) mean AUC0-24 values were 29.75 +/- 19.92 ng h ml(-1) and 46.13 +/- 38.50 ng h ml(-1) on day 1 and day 5, respectively. Histamine-induced wheals and flares were significantly more effectively suppressed by emedastine and cetirizine than placebo. At pharmacokinetic steady-state levels, no significant difference could be found in the potency between cetirizine and emedastine (2 mg b.i.d.).

CONCLUSION

Emedastine displays pharmacodynamic properties comparable with cetirizine and therefore qualifies as a safe and alternative compound with H1-receptor antagonist properties. Additional larger studies may be needed to substantiate potential benefits of cetirizine over emedastine after single-dose administration.

[3D-spectrogram of the doppler signal in real time]

AIM

Doppler signals are normally displayed as an x/y-graph. The frequency is plotted in the y-direction, and the intensity is represented by the brightness. This represents less information than is contained in the acoustic signal: often one can hear more one can see. We are investigating the question as to whether it is feasible to render the complete information visible without the use of expensive additional equipment.

METHOD

The sound card (SB16 P&P value edition) in a Pentium-PC (200 MHz 32 MB RAM) was used as a 16 bit dual channel a/d converter and connected to the ultrasound system Sonoline Elegra (Siemens, Erlangen, Germany). We used a standard 32 bit dual channel real-time FFT-software (SpectraPro, Sound Technology, California) to display a 3D-spectrogram on the PC-screen in real-time mode. This system was first tested on a flow model both with laminar steady flow and with pulsatile flow. Following this, measurements were made of the arteries and veins in healthy volunteers.

RESULTS

In the 3D-Spectrogram the character of the flow can easily be seen. The quantitative parameters of velocity (Doppler frequency), direction and intensity of flow can be readily determined. Additional information about quality of flow, erythrocyte clusters and changes occurring in areas of slight stenoses can be used for diagnostic evaluation. The orthograde and retrograde flow are displayed separately using the dual channel technique. The arterial and venous flow in small and closely neighbouring vessels, such as the central retinal artery and vein, can easily be differentiated. The venous flow in particular is more turbulent in the 3D-spectrogram than would be expected from the normal display mode.

CONCLUSION

The 3D-spectrogram provides much additional information in comparison with the normal Doppler spectrogram of the ultrasound system. This 3D-spectrogram can be easily obtained using inexpensive standard hard- and software.

Na(+) and K(+) concentrations, extra- and intracellular voltages, and the effect of TTX in hypoxic rat hippocampal slices

Severe hypoxia causes rapid depolarization of CA1 neurons and glial cells that resembles spreading depression (SD). In brain slices in vitro, the SD-like depolarization and the associated irreversible loss of function can be postponed, but not prevented, by blockade of Na(+) currents by tetrodotoxin (TTX). To investigate the role of Na(+) flux, we made recordings from the CA1 region in hippocampal slices in the presence and absence of TTX. We measured membrane changes in single CA1 pyramidal neurons simultaneously with extracellular DC potential (V(o)) and either extracellular [K(+)] or [Na(+)]; alternatively, we simultaneously recorded [Na(+)](o), [K(+)](o), and V(o). Confirming previous reports, early during hypoxia, before SD onset, [K(+)](o) began to rise, whereas [Na(+)](o) still remained normal and V(o) showed a slight, gradual, negative shift; neurons first hyperpolarized and then began to gradually depolarize. The SD-like abrupt negative DeltaV(o) corresponded to a near complete depolarization of pyramidal neurons and an 89% decrease in input resistance. [K(+)](o) increased by 47 mM and [Na(+)](o) dropped by 91 mM. Changes in intracellular Na(+) and K(+) concentrations, estimated on the basis of the measured extracellular ion levels and the relative volume fractions of the neuronal, glial, and extracellular compartment, were much more moderate. Because [Na(+)](o) dropped more than [K(+)](o) increased, simple exchange of Na(+) for K(+) cannot account for these ionic changes. The apparent imbalance of charge could be made up by Cl(-) influx into neurons paralleling Na(+) flux and release of Mg(2+) from cells. The hypoxia-induced changes in interneurons resembled those observed in pyramidal neurons. Astrocytes responded with an initial slow depolarization as [K(+)](o) rose. It was followed by a rapid but incomplete depolarization as soon as SD occurred, which could be accounted for by the reduced ratio, [K(+)](i)/[K(+)](o). TTX (1 microM) markedly postponed SD, but the SD-related changes in [K(+)](o) and [Na(+)](o) were only reduced by 23 and 12%, respectively. In TTX-treated pyramidal neurons, the delayed SD-like depolarization took off from a more positive level, but the final depolarized intracellular potential and input resistance were not different from control. We conclude that TTX-sensitive channels mediate only a fraction of the Na(+) influx, and that some of the K(+) is released in exchange for Na(+). Even though TTX-sensitive Na(+) currents are not essential for the self-regenerative membrane changes during hypoxic SD, in control solutions their activation may trigger the transition from gradual to rapid depolarization of neurons, thereby synchronizing the SD-like event.

Discrimination between SRP- and SecA/SecB-dependent substrates involves selective recognition of nascent chains by SRP and trigger factor

Besides SecA and SecB, Escherichia coli cells possess a signal recognition particle (SRP) to target exported proteins to the SecY translocon. Using chemical and site-specific cross-linking in vitro, we show that SRP recognizes the first signal anchor sequence of a polytopic membrane protein (MtlA) resulting in cotranslational targeting of MtlA to SecY and phospholipids of the plasma membrane. In contrast, a possible interaction of SRP with the secretory protein pOmpA is prevented by the association of trigger factor with nascent pOmpA. Trigger factor also prevents SecA from binding to the first 125 amino acids of pOmpA when they are still associated with the ribosome. Under no experimental conditions was SecA found to interact with MtlA. Likewise, virtually no binding of trigger factor to ribosome-bound MtlA occurs even in the complete absence of SRP. Collectively, our results indicate that at the stage of nascent polypeptides, polytopic membrane proteins are selected by SRP for co-translational membrane targeting, whereas secretory proteins are directed into the SecA/SecB-mediated post-translational targeting pathway by means of their preferential recognition by trigger factor.

Effect of zopiclone and temazepam on sleep EEG parameters, psychomotor and memory functions in healthy elderly volunteers

RATIONALE

The increased prevalence of sleep disturbance in old age is accompanied by a higher prescription rate of hypnotics, predominantly benzodiazepines in the elderly. In young volunteers zopiclone exerts a beneficial effect on sleep continuity without suppression of SWS and REM sleep; psychomotor performance and vigilance seemed to be less impaired than under classical benzoediazepines.

OBJECTIVE

The present study investigates the effects of zopiclone on sleep EEG and cognitive performance in comparison to temazepam and placebo in the elderly population.

METHODS

Single oral doses of zopiclone (7.5 mg), temazepam (20 mg) and placebo were administered in a randomized double-blind, completely counterbalanced cross-over design to 12 healthy elderly men and women (65.9 +/- 3.6 years, range 60-70 years). On each of the 3 study nights a sleep EEG was registered from 10 p.m. to 6.30 a.m. and cognitive performance tests were applied at 8 p.m., 2 a.m. (when subjects were awake for 30 min), 7 a.m. and 9 a.m.

RESULTS

After zopiclone treatment, sleep continuity had significantly improved and sleep stage 4 was increased compared to temazepam and placebo. In addition, both active substances significantly reduced REM density. Neither active compound substantially altered psychomotor and memory performance.

CONCLUSIONS

Zopiclone and temazepam can be considered as effective hypnotics in elderly subjects when administered in that dosage. The superiority of zopiclone on sleep architecture may be related to a more specific action of zopiclone at the GABA-A benzodiazepine receptor complex. The suppression of REM density by both compounds and their subtle effects on cognition may reflect a GABAergic mediated reduction of cholinergic neuro-transmission.

Ischemia after carotid endarterectomy: comparison between transcranial Doppler sonography and diffusion-weighted MR imaging

BACKGROUND AND PURPOSE

Hyperintense signals on diffusion-weighted MR images (DWIs) are believed to correspond accurately with cerebral ischemic events. Intraoperative transcranial Doppler sonography (TCD) can reveal hemodynamic and embolic events during carotid endarterectomy (CEA). Our purpose was to determine whether the occurrence of hyperintense signals on postoperative DWIs corresponds to intraoperative embolic or hemodynamic events.

METHODS

Seventy-seven CEAs were monitored intraoperatively with TCD to record blood flow velocity changes after cross clamping to ascertain the presence of adequate collateral flow and to record microembolic signals. DWI was used to classify the hemisphere ipsilateral to the CEA by type: 0, no lesions (n = 51); I, cortical lesions only (n = 2); II, subcortical white matter lesions only (n = 6); III, mixed type with cortical and subcortical lesions (n = 11); IV, large territorial infarcts (n = 6); and V, other types of lesions (n = 1).

RESULTS

Neither the five clinical events (one transient ischemic attack, two minor strokes, and two major strokes) nor any DWI type (I-V) showed a relationship to blood velocity decreases after cross clamping or, in patients who were selectively shunted, to total ischemic time necessary for shunt insertion and removal. Total microembolic signal count was significantly higher in the five CEAs with clinical events than in those without. It was also higher on the DWIs showing a hyperintense lesion as compared with DWIs showing no lesion.

CONCLUSION

Apart from lesions corresponding to clinical deficits, CEA is associated with a substantial number of small areas of brain tissue at risk for irreversible ischemia. The main cause of intraoperative stroke seems to be embolism, suggesting that microembolic signals in CEA are highly relevant events for brain tissue.

Third-harmonic generation microscopy by use of a compact, femtosecond fiber laser source

We demonstrate the first use, to our knowledge, of a compact, diode-pumped, femtosecond fiber laser for third-harmonic generation (THG) microscopy. We discuss the utility of this technique, as well as the technical issues involved in using this compact source, and demonstrate the first use, to our knowledge, of imaging by THG backlighting.

Sequence and analysis of chromosome 4 of the plant Arabidopsis thaliana

The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we report one of the first milestones of this project, the sequence of chromosome 4. Analysis of 17.38 megabases of unique sequence, representing about 17% of the genome, reveals 3,744 protein coding genes, 81 transfer RNAs and numerous repeat elements. Heterochromatic regions surrounding the putative centromere, which has not yet been completely sequenced, are characterized by an increased frequency of a variety of repeats, new repeats, reduced recombination, lowered gene density and lowered gene expression. Roughly 60% of the predicted protein-coding genes have been functionally characterized on the basis of their homology to known genes. Many genes encode predicted proteins that are homologous to human and Caenorhabditis elegans proteins.

Glimepiride (Hoe490) inhibits the rilmakalim induced decrease in intracellular free calcium and contraction of isolated heart muscle cells from guinea pigs to a lesser extent than glibenclamide

Glibenclamide is a potent inhibitor of the ATP-dependent potassium channel. Opening of the ATP-dependent potassium channel is regarded as a mechanism of ischemic preconditioning. This in vitro study examines the influence of glibenclamide and glimepiride, a new sulfonylurea, on the negative inotropic action of the potassium channel opener rilmakalim in isolated ventricular myocytes. Cardiac myocytes were isolated from adult guinea pig hearts by collagenase perfusion and incubated with rilmakalim (concentration range 0.1-12.0 microM), glibenclamide (concentration range 0.03-3.0 microM) plus rilmakalim (3.0 or 7.5 microM), and glimepiride (0.03-9.0 microM) plus rilmakalim (3.0 or 7.5 microM) and paced by electrical field stimulation. Contractility of the myocytes was evaluated by digital image analysis, intracellular free calcium was determined by means of fura-2 fluorescence measurements, and cell viability was assessed morphologically as well as by measurement of lactate dehydrogenase activity. Rilmakalim reduced the systolic intracellular free calcium and contractility of ventricular myocytes in a concentration dependent manner. This effect was antagonized by glibenclamide at lower concentrations (0.3 microM) than glimepiride (3.0 microM). The smaller antagonistic action of glimepiride on the negative inotropic effect of rilmakalim as compared with glibenclamide most likely reflects a less potent inhibition of ATP-dependent potassium channels by glimepiride.

Improving protein identification from peptide mass fingerprinting through a parameterized multi-level scoring algorithm and an optimized peak detection

We have developed a new algorithm to identify proteins by means of peptide mass fingerprinting. Starting from the matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) spectra and environmental data such as species, isoelectric point and molecular weight, as well as chemical modifications or number of missed cleavages of a protein, the program performs a fully automated identification of the protein. The first step is a peak detection algorithm, which allows precise and fast determination of peptide masses, even if the peaks are of low intensity or they overlap. In the second step the masses and environmental data are used by the identification algorithm to search in protein sequence databases (SWISS-PROT and/or TrEMBL) for protein entries that match the input data. Consequently, a list of candidate proteins is selected from the database, and a score calculation provides a ranking according to the quality of the match. To define the most discriminating scoring calculation we analyzed the respective role of each parameter in two directions. The first one is based on filtering and exploratory effects, while the second direction focuses on the levels where the parameters intervene in the identification process. Thus, according to our analysis, all input parameters contribute to the score, however with different weights. Since it is difficult to estimate the weights in advance, they have been computed with a generic algorithm, using a training set of 91 protein spectra with their environmental data. We tested the resulting scoring calculation on a test set of ten proteins and compared the identification results with those of other peptide mass fingerprinting programs.

Effects of an oxidizing agent (hydrogen peroxide) on the glutathione system in epidermal cells of Allium cepa L. investigated by histochemical staining

The glutathione system in epidermal cells of Allium cepa L. was measured by a quantitative image analysis method, using histochemical staining by monochlorobimane. Blockage of thiol groups with N-ethylmaleimide decreased fluorescence to a small rest fluorescence of maximum 5%. Pre-treatment with dithiothreitol increased fluorescence yield in all cells compared to the monochlorobimane treatment alone. These results correspond to the blockage or the reduction of the total pool of glutathione in the cells. After treatment with N-ethylmaleimide and subsequent incubation with dithiothreitol followed by labelling with bimane a low fluorescence yield was observed which correspond to the proportion of GSSG. Specimens that were incubated in H2O2 prior to the treatments described above exhibited a decrease in total glutathione and in reduced glutathione and an increase in the proportion of GSSG compared to the control.

Hepatocanalicular bile salt export pump deficiency in patients with progressive familial intrahepatic cholestasis

BACKGROUND & AIMS

Progressive familial intrahepatic cholestasis (PFIC), an inherited liver disease of childhood, is characterized by cholestasis and either normal or increased serum gamma-glutamyltransferase activity. Patients with normal gamma-glutamyltransferase activity have mutations of the FIC1 locus on chromosome 18q21 or mutations of the BSEP gene on chromosome 2q24. Also, patients with bile acid synthesis defects have low gamma-glutamyltransferase activity. We investigated expression of the bile salt export pump (BSEP) in liver samples from patients with a PFIC phenotype and correlated this with BSEP gene mutations.

METHODS

BSEP and multidrug resistance protein 2 (MRP2) expressions were studied by immunohistochemistry in liver specimens of 28 patients and BSEP gene mutation analysis in 19 patients. Bile salt kinetics were studied in 1 patient.

RESULTS

Sixteen of 28 liver samples showed no canalicular BSEP staining. Staining for MRP2 showed a normal canalicular pattern in all but 1 of these samples. Ten of 19 patients showed BSEP gene mutations; BSEP protein expression was lacking in all 10 patients. No mutations were found in 9 of 19 patients, and in all except 1, BSEP protein expression was normal. Bile salt concentration in bile of BSEP-negative/MRP2-positive PFIC patients was 0.2 +/- 0.2 mmol/L (n = 9; <1% of normal) and in BSEP-positive PFIC patients 18.1 +/- 9.9 mmol/L (n = 3; 40% of normal). The kinetic study confirmed the dramatic decrease of bile salt secretion in BSEP-negative patients.

CONCLUSIONS

The findings show a close correlation between BSEP gene mutations and canalicular BSEP expression. Biliary secretion of bile salts is greatly reduced in BSEP-negative patients.