Comparison of oral anticoagulation by vitamin-K antagonists and non-vitamin-K antagonists for treatment of leaflet thickening after transcatheter aortic valve implantation (TAVI).

INTRODUCTION: Hypoattenuated leaflet thickening (HALT), as identified by CT imaging, is not infrequent after transcatheter aortic valve implantation (TAVI). The best choice of oral anticoagulation is unknown. We compared the effectiveness of Direct Oral AntiCoagulants (DOAC) and Vitamin-K Antagonists (VKA) to resolve HALT in patients with serial CT aquisitions. METHODS: A total of 46 consecutive TAVI patients in whom anticoagulation had been initiated because of HALT and who underwent follow-up CT were identified. Indication and type of anticoagulation was according to physician discretion. Patients on DOAC were compared to VKA therapy regarding resolution of HALT. RESULTS: Mean age of the 46 patients was 80 ± 6 years (59% men), and the mean duration of anticoagulation was 156 days. Overall, 41 patients (89%) showed resolution of HALT with anticoagulation therapy, whereas HALT persisted in 5 patients (11%). Resolution of HALT was seen in 26 out of 30 (87%) patients receiving VKA and in 15 out of 16 (94%) patients receiving DOAC, respectively. Groups did not differ regarding age, cardiovascular risk factors, TAVI prosthesis type and size or duration of anticoagulation (all p > 0.05). CONCLUSION: Anticoagulation therapy resolves leaflet thickening after TAVI in most patients. Non-Vitamin-K antagonists seem to be an effective alternative to Vitamin-K antagonists. This finding needs to be confirmed in larger prospective trials.

Early-onset coronary atherosclerosis in patients with low levels of omega-3 fatty acids.

OBJECTIVES: Coronary artery calcification (CAC) can reliably predict cardiovascular events. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are thought to inhibit vascular calcification on a cellular level and in animal models, however, the correlation in humans is controversial. METHODS: In symptomatic patients, CAC was quantified according to Agatstons' method using non-contrast coronary CT. We assessed the association of EPA and DHA with early-onset coronary atherosclerosis, defined as presence of CAC above the 75th Agatston-Score (AS) percentile in sex adjusted age categories. Erythrocyte fatty acid composition was analyzed with a standardized methodology. The percentage of EPA and DHA in relation to all fatty acids present in the erythrocyte membrane is regarded the Omega-3 Index®. RESULTS: Among 71 patients, 51 were below and 20 were above the 75th AS-percentile. No differences were seen in age, gender, cardiovascular risk factors, and relevant medication. In univariable analysis, significantly lower values for EPA (0.77%[0.63; 0.97] vs. 0.93%[0.72; 1.21]; p = 0.045), DHA (4.90%[4.12; 5.57] vs. 5.50%[4.58; 6.52]; p = 0.038) and the Omega-3 Index (5.73%[4.75; 6.35] vs. 6.22%[5.46; 7.71]; p = 0.034) were seen in patients above the 75th AS-percentile. All other fatty acids showed no significant differences. In multivariable analysis, the Omega-3 Index showed a significant inverse association with early onset of CAC (OR: 0.533 (95%CI: 0.303-0.938; p = 0.029)), independent of age, gender, statin use, and creatinine level (all p > 0.05). CONCLUSIONS: Low levels of EPA and DHA (Omega-3 Index) are associated with early-onset coronary atherosclerosis. This finding needs to be validated in larger cohorts and might help understand the beneficial cardiovascular effects of omega-3 fatty acids.

CT-derived left ventricular global strain: a head-to-head comparison with speckle tracking echocardiography.

We assessed CT-derived left ventricular strain in a cohort of patients referred for transcatheter aortic valve implantation (TAVI) and validated it against 2 dimensional speckle tracking echocardiography as the gold standard. 65 consecutive patients with symptomatic aortic valve stenosis referred for CT imaging prior to TAVI were included in this analysis. For all patients, retrospectively ECG-gated multi-phase functional CT data sets acquired with identical reconstruction parameters were available. All data sets were acquired using a third generation dual source system. In all patients, multiphase reconstructions in increments of 10% of the cardiac cycle were rendered (slice thickness 0.75, increment 0.5 mm, medium smooth reconstruction kernel) and transferred to a dedicated workstation (Ziostation2, Ziosoft Inc., Tokyo, Japan). Additional functional reconstructions for dynamic assessment and quantification of strain were processed. Multiplanar reconstructions (MPR) of the left ventricle similar to standard echocardiographic 4, 2 and apical 3 chamber views were rendered in CT. Similar to echocardiographic longitudinal strain, the perimeter of the left ventricle was manually traced within the myocardium and peak maximal shortening as a parameter representing longitudinal strain was calculated for each view and averaged to obtain a marker for global longitudinal strain (CT perimeter-derived strain). Furthermore, for quantification of 3-dimensional strain, endocardial and epicardial borders of myocardium were marked in six short axis views and peak maximum 3- dimensional strain of the myocardium was calculated in standard six basal, six mid and four apical segments. 3-dimensional strain values of the 16 standard segments as well as perimeter-derived strain values in the three standard windows were averaged to obtain global strain. Echocardiography was performed in all patients before CT data acquisition. Digital loops were acquired from three apical views (four-, two-, and three chamber views). For assessment of 2 dimensional global longitudinal strain (GLS), recordings were processed with acoustic-tracking software allowing offline semiautomated speckle-based strain analyses. The mean age of all 65 patients was 81 ± 5 years. The mean echocardiographic ejection fraction and mean echocardiographic GLS were 50 ± 12% and -13.6 ± 4.5%, respectively. The mean CT-derived peak 3-dimensional global strain and mean peak strain derived by perimeter was 43.2 ± 13.5% and -11.2 ± 3.5%, respectively. Both CTderived global 3D-strain and perimeter derived strain showed a significant correlation to GLS derived by echocardiography (r = -0.8, p < 0.0001 for 3D strain and r = 0.71, p < 0.0001 for perimeter-derived strain). Bland-Altman analysis showed a systematic underestimation (i. e. worse strain values) of CT perimeter-derived strain compared to GLS by echocardiography (mean difference -2.4% with 95% limits of agreement between 4% to -9%). ROC Curve analysis assuming a normal GLS when less than -18% showed that a CT-derived peak 3-dimensional global strain cut-off-value of 45% has a sensitivity of 91% and a specificity of 60% for detecting normal left ventricular strain (AUC 0.81, p = 0.001). For CT perimeter-derived strain, a cut-off value of -12%-assuming a normal echocardiographic GLS when less than -18%-achieved a sensitivity of 82% and a specificity of 61% (AUC of 0.82, p = 0.001) for detecting abnormal left ventricular strain. Using dedicated software, assessment of CT-derived left ventricular strain is feasible and comparable to strain derived by echocardiographic 2 dimensional speckle tracking.

CT-derived left ventricular global strain in aortic valve stenosis patients: A comparative analysis pre and post transcatheter aortic valve implantation.

INTRODUCTION: We assessed the potential of CT strain to detect changes in myocardial function in patients referred for TAVI pre and post intervention. PATIENTS AND METHODS: 25 consecutive patients with symptomatic aortic valve stenosis in whom TAVI had been performed were included in this analysis. Functional CT data sets acquired before and 3 to 6 months after TAVI were available. Multiphase reconstructions in increments of 10% of the cardiac cycle were rendered and transferred to a dedicated workstation (Ziostation2, Ziosoft Inc., Tokyo, Japan). For quantification of left ventricular strain, multiplanar reconstructions of the left ventricle in standard 4 chamber, 2 chamber as well as apical 3 chamber views were rendered. The perimeter of the left ventricle was traced dynamically through the cardiac cycle. Peak strain was calculated for each patient pre and post intervention. Furthermore, for quantification of 3-dimensional maximum principal strain, 2 volumetric regions of interests (VOI) were placed per each basal, mid and apical segment of the previously mentioned MPRs and peak maximal principal strain was calculated. Maximum principal strain as well as perimeter-derived longitudinal strain values in the three standard windows were averaged to obtain global strain. RESULTS: 25 patients were included in this analysis (mean age 78 ±â€¯9 years, 13 males). Peak global maximum principal strain was significantly higher at follow-up compared to baseline (0.46 ±â€¯0.19 vs. 0.59 ±â€¯0.18, respectively, p = 0.001). Similarly global longitudinal strain derived by perimeter was significantly lower - implying better contraction - compared to baseline (-8.6% ±â€¯2.8% vs. -9.8% ±â€¯2.6%, respectively, p = 0.006). CONCLUSION: Using dedicated software, assessment of CT derived left ventricular strain is feasible. In patients treated with transcatheter aortic valve replacement, CT-derived parameters of global myocardial strain improve onshort-term follow-up.

Leaflet thrombosis following transcatheter aortic valve implantation.

BACKGROUND: Transcatheter aortic valve implantation (TAVI) is increasingly being offered to high-risk patients with symptomatic aortic valve stenosis. Recent reports have suggested a high incidence of subclinical leaflet thrombosis following bioprosthestic aortic valve replacement. We report the frequency and clinical presentation of leaflet thrombosis identified by cardiac CT in patients referred for follow-up contrast enhanced CT angiography following TAVI. METHODS: 91 consecutive patients referred for follow-up contrast-enhanced CT angiography following TAVI were screened for inclusion in this analysis. Out of these, 13 patients were excluded. All CT examinations were performed using a 2nd or a 3rd generation dual-source system (Somatom Definition Flash/Force, Forchheim, Germany). In all patients, retrospectively ECG-gated spiral acquisition with tube modulation was performed to allow for assessment of leaflet motion. All prostheses were analyzed for presence of leaflet thrombosis defined as hypo-attenuated leaflet thickening with or without leaflet restriction. Post-procedural antithrombotic regimen as well as symptom status was documented in all patients. RESULTS: 78 consecutive patients (35 males, 81 ± 4 years) were analyzed. TAVI had been performed in all patients (76 transfemoral access, 2 transapical access) with either balloon-expandable prostheses (4 Sapien XT, 64 Sapien 3) or self-expandable prostheses (5 SJM Portico, 5 Symetis Acurate). Follow-up CT angiography was performed at a median of 4 months following index procedure (Interquartile range 1 month). Leaflet thrombosis was detected in 18 patients (23%, 14 Sapien 3, 1 Sapien XT, 2 SJM Portico, 1 Symetis Acurate). In patients with leaflet thickening on CT, only 11% were on either oral anticoagulation or new oral anticoagulants versus 50% for patients with no leaflet thickening (p 0.002). In patients with leaflet thrombosis, 3 leaflets were affected in 5 patients, 2 leaflets in 5 patients and in 8 patient only 1 leaflet was affected. Clinical symptoms (angina, dyspnea or both) were reported in 2/18 patients with leaflet thrombosis (11%) and in both patients a significant increase of the mean echocardiographic gradient over the prosthesis was documented. The peak and mean echocardiographic gradients obtained at the day of CT examination was significantly higher in symptomatic patients versus asymptomatic patients (peak 46 ± 7 vs. 23 ± 11 mmHg, mean 29 ± 7 vs. 12 ± 6 mmHg, p = 0.01 and 0.002, respectively). Follow-up CT was available for 4 patients with complete resolution of the hypo-attenuated leaflet thickening following treatment. CONCLUSION: Leaflet thrombosis following TAVI is a relatively frequent finding in patients referred for contrast enhanced CT angiography following TAVI. In the majority of patients it follows a subclinical course and is substantially more frequent in individuals who are not on oral anticoagulation. However, in patients with relevant increase in prosthetic gradients, symptomatic presentations are possible.

Progranulin levels in status epilepticus as a marker of neuronal recovery and neuroprotection.

INTRODUCTION: Recently, a mouse model showed that progranulin, a mediator in neuroinflammation and a neuronal growth factor, was elevated in the hippocampus after status epilepticus (SE). This elevated level might mirror compensating neuronal mechanisms after SE. Studies concerning neuronal recovery and neuroprotective mechanisms after SE in humans are scarce, so we tested for progranulinin the cerebrospinal fluid (CSF) after various types of SE. METHOD: We performed a retrospective analysis of progranulin levels in CSF in patients (n = 24) who underwent lumbar puncture as part of diagnostic workup after having SE and in patients after having one single tonic-clonic seizure who comprised the control group (n = 8). RESULTS: In our group with SE, progranulin levels in CSF were not significantly elevated compared to our control group. Furthermore, there was no correlation between progranulin levels and the time interval between lumbar puncture and SE. Additionally, in cases of higher CSF progranulin levels, we found no impact on the clinical outcome after SE. CONCLUSION: Although our cohort is heterogeneous and not fully sufficient, we conclude that progranulin in CSF is not elevated after SE in our cohort. Therefore, our results do not suggest a change in cerebral progranulin metabolism as a possible neuroregenerative or neuroprotective mechanism in humans after SE in acute and subacute phases. A larger cohort study is needed to further strengthen this result. This article is part of a Special Issue entitled "Status Epilepticus".

Eutrophication causes speciation reversal in whitefish adaptive radiations.

Species diversity can be lost through two different but potentially interacting extinction processes: demographic decline and speciation reversal through introgressive hybridization. To investigate the relative contribution of these processes, we analysed historical and contemporary data of replicate whitefish radiations from 17 pre-alpine European lakes and reconstructed changes in genetic species differentiation through time using historical samples. Here we provide evidence that species diversity evolved in response to ecological opportunity, and that eutrophication, by diminishing this opportunity, has driven extinctions through speciation reversal and demographic decline. Across the radiations, the magnitude of eutrophication explains the pattern of species loss and levels of genetic and functional distinctiveness among remaining species. We argue that extinction by speciation reversal may be more widespread than currently appreciated. Preventing such extinctions will require that conservation efforts not only target existing species but identify and protect the ecological and evolutionary processes that generate and maintain species.

Verbal episodic memory and endogenous estradiol: an association in patients with mild cognitive impairment and Alzheimer's disease.

In the continuum of patients with Alzheimer's disease (AD), mild cognitive impairment (MCI), and normal controls, a possible association of verbal memory and endogenous estradiol (E(2)) levels was investigated. Verbal episodic memory was measured with a german version of the California verbal memory test (CVLT). Results were controlled for apolipoprotein E (ApoE) phenotype. We studied 37 controls, 32 MCIs and 117 ADs. Groups differed in all trials of the CVLT (P < 0.001) and in E(2) levels (P < 0.001). E2 levels differed significantly between groups only among females (P < 0.001). In females correcting for age and ApoE, there was an overall correlation between CVLT delayed recall and level of E(2) (P = 0.025). Stepwise regression analyses found E(2) level to be a significant predictor for CVLT delayed recall (P < 0.001). It may be concluded that lower E(2) levels occur more in the course of the disease than may be considered as a risk factor per se.

Patterns of morphological changes and hybridization between sympatric whitefish morphs (Coregonus spp.) in a Swiss lake: a role for eutrophication?

Whitefish, genus Coregonus, show exceptional levels of phenotypic diversity with sympatric morphs occurring in numerous postglacial lakes in the northern hemisphere. Here, we studied the effects of human-induced eutrophication on sympatric whitefish morphs in the Swiss lake, Lake Thun. In particular, we addressed the questions whether eutrophication (i) induced hybridization between two ecologically divergent summer-spawning morphs through a loss of environmental heterogeneity, and (ii) induced rapid adaptive morphological changes through changes in the food web structure. Genetic analysis based on 11 microsatellite loci of 282 spawners revealed that the pelagic and the benthic morph represent highly distinct gene pools occurring at different relative proportions on all seven known spawning sites. Gill raker counts, a highly heritable trait, showed nearly discrete distributions for the two morphs. Multilocus genotypes characteristic of the pelagic morph had more gill rakers than genotypes characteristic of benthic morph. Using Bayesian methods, we found indications of recent but limited introgressive hybridization. Comparisons with historical gill raker data yielded median evolutionary rates of 0.24 haldanes and median selection intensities of 0.27 for this trait in both morphs for 1948-2004 suggesting rapid evolution through directional selection at this trait. However, phenotypic plasticity as an alternative explanation for this phenotypic change cannot be discarded. We hypothesize that both the temporal shifts in mean gill raker counts and the recent hybridization reflect responses to changes in the trophic state of the lake induced by pollution in the 1960s, which created novel selection pressures with respect to feeding niches and spawning site preferences.

Divergence along a steep ecological gradient in lake whitefish (Coregonus sp.).

To understand mechanisms structuring diversity in young adaptive radiations, quantitative and unbiased information about genetic and phenotypic diversity is much needed. Here, we present the first in-depth investigation of whitefish diversity in a Swiss lake, with continuous spawning habitat sampling in both time and space. Our results show a clear cline like pattern in genetics and morphology of populations sampled along an ecological depth gradient in Lake Neuchâtel. Divergent natural selection appears to be involved in shaping this cline given that trait specific P(ST)-values are significantly higher than F(ST)-values when comparing populations caught at different depths. These differences also tend to increase with increasing differences in depth, indicating adaptive divergence along a depth gradient, which persists despite considerable gene flow between adjacent demes. It however remains unclear, whether the observed pattern is a result of currently stable selection-gene flow balance, incipient speciation, or reverse speciation due to anthropogenic habitat alteration causing two formerly divergent species to collapse into a single gene pool.

How normal is abnormal? Discrimination between deformations and natural variation in gonad morphology of European whitefish Coregonus lavaretus.

The gonad morphology of whitefish Coregonus lavaretus collected in Lake Thun, Switzerland, and two neighbouring lakes was assessed in order to differentiate between 'normal' and 'abnormal' character states of gonad morphology, which had been previously described in C. lavaretus from Lake Thun (constrictions, asymmetries, aplasia, compartmentations, fusions and hermaphroditism). In total, 4668 fish were collected and analysed using two complementary sampling schemes: (1) monthly samples of catches by the commercial fishermen and (2) samples of ripe spawners of all known 33 spawning sites of the three lakes. Considerable variation in gonad morphology in C. lavaretus populations of all lakes was found. Notably, all deviation types were observed in fish of all three lakes. Asymmetries and constrictions were frequent in all three lakes and showed systematic differences in frequency between the two sampling strategies. This indicates that asymmetries and constrictions represent to a large extent natural variation in gonad morphology of C. lavaretus and are also prone to considerable measurement error. In contrast, aplasia, fusions, compartmentations and hermaphroditism occurred predominantly in one C. lavaretus form of Lake Thun and in particular in populations spawning at great depths. This suggests that these deviation types are probably reliable indicators for gonad deformations and supports the interpretation that Lake Thun harbours a unique case of deformed gonads in C. lavaretus of yet unknown origin.

Gender-specificities in Alzheimer's disease and mild cognitive impairment.

BACKGROUND: Amnestic Mild Cognitive Impairment (MCI) is a condition with an increased risk for developing Alzheimer's disease (AD). Presently, gender differences are neglected in the assessment of MCI and AD. METHODS: We examined verbal and visuospatial episodic memory in 143 subjects diagnosed as healthy controls (HC; N = 48, Mini-Mental State Examination (MMSE) 29.2 +/- 1.0 (mean +/- standard deviation)), MCI (N = 43,MMSE 28.5 +/- 1.4), and AD (N = 49, MMSE 25.1 +/- 2.2). FINDINGS: Female HC and MCI subjects performed better on verbal episodic memory tasks than males. In contrast, visuospatial episodic memory was better in male than female AD patients. CONCLUSIONS: We interpret the results in light of a gender-specific cognitive reserve and conclude that the gender-specificity of neuropsychological performance needs to be accounted for in clinical diagnosis of Alzheimer's disease.

Genetic analysis of potential postglacial watershed crossings in Central Europe by the bullhead (Cottus gobio L.).

Natural colonizations across watersheds have been frequently proposed to explain the present distributions of many freshwater fish species. However, detailed studies of such potential watershed crossings are still missing. Here, we investigated potential postglacial watershed crossings of the widely distributed European bullhead (Cottus gobio L.) in two different areas along the Rhine-Rhône watershed using detailed genetic analysis. The main advantage of studying bullheads vs. other freshwater fish species is that their distribution has been lightly influenced by human activities and as such, interpretations of colonization history are not confounded by artificial transplantations. The genetic analyses of eight microsatellite loci revealed strong genetic similarities between populations of both sides of the Rhine-Rhône watershed in the Lake Geneva area, giving strong evidence for a natural watershed crossing of bullheads from the upper Rhine drainage into the Rhône drainage in the Lake Geneva area likely facilitated by the retreat of the glaciers after the last glacial maximum some 20,000 years ago. Populations from the Lake Geneva basin were genetically more similar to populations from across the watershed in the upper Rhine drainage than to populations further downstream in the lower Rhône. In contrast, populations from Belfort, an area, which was not covered by ice during the last glacial maximum, showed strong genetic differentiation between populations of the upper Rhine and Rhône drainages. Based on our results on the bullhead, we propose that glacial retreat may have eased the dispersal of numerous European freshwater fish species across several geological boundaries.

[18F]FDG-PET in patients with Alzheimer's disease: marker of disease spread.

BACKGROUND: It is not known yet whether temporoparietal glucose hypometabolism in patients with probable Alzheimer's disease (AD) reflects disease severity or different subtypes of patients. METHODS: Twenty-five subjects with mild probable AD [NINCDS-ADRDA criteria; age 65.8 +/- 9.3 years (mean +/- SD); Mini-Mental State Examination (MMSE) 26.0 +/- 3.3] were investigated. [(18)F]FDG-PET data were analyzed visually with raters blinded to the diagnosis and with a quantitative analysis in the region of interest on individual anatomically normalized PET scans. RESULTS: Thirteen of 25 patients showed temporoparietal hypometabolism on visual inspection (PET+; age 65.7 +/- 10.7), 12 patients had normal FDG-PET results (PET-; age 65.9 +/- 8.0; n.s.). The MMSE and immediate reproduction of the Wechsler Memory Scale (WMS-R-I) were 27.7 +/- 1.9 and 31.1 +/- 6.1 in the PET- vs. 24.5 +/- 3.6 (p = 0.012) and 22.0 +/- 7.4 (p = 0.006) in the PET+ group. Immediate and delayed recall in the California Verbal Learning Test and delayed reproduction in the Wechsler Memory Scale were alike. Regression analysis revealed a significant correlation of temporoparietal glucose metabolism with the block span (r = 0.60; p < 0.01) and the WMS-R-I (r = 0.68; p < 0.01) but not with measures of hippocampal function. CONCLUSIONS: Temporoparietal glucose metabolism in patients with very mild AD is a sign of disease spread beyond the temporal lobe. This may aid in establishing objective parameters for future therapeutic studies.

Hippocampal activations during repetitive learning and recall of geometric patterns.

Hippocampal activation is required for episodic memory. Encoding and retrieval of novel and memorable items have been related to different locations in the hippocampus; however, the data remain ambiguous. The application of a newly designed keyboard allowed investigation of brain activation during encoding and free immediate and delayed recall with functional magnetic resonance imaging (fMRI) in young healthy controls (n = 12). Because of the repetitive learning and recall conditions, an individual learning gradient was used to contrast neural activity at different individual levels of novelty. During learning, subjects were asked to memorize 10 geometric patterns requiring the establishment of intra-item associations for memorization. After learning, subjects were asked to recall the items actively via the keyboard. Learning and recall were alternated five times. Delayed recall was scanned about 15 min after the fifth immediate recall condition without subjects having seen the items again. Left-sided anterior hippocampal activity was observed during conditions of initial learning as well as maximum recall. Neural activity during delayed recall did not reveal hippocampal responses and was characterized by a transition of neural activity from occipitoparietal regions to bilateral temporal cortices. We conclude that both lateralization and segregation depend on the specific relational characteristics of the stimuli requiring establishment of intra-item associations for encoding as well as retrieval. The absence of hippocampal activation during delayed recall together with the increase of lateral temporal involvement possibly corresponds with an emerging transition from episodic to long-term memory.

Induction of dedifferentiated clones of LLC-PK1 cells upon long-term exposure to dichlorovinylcysteine.

Dichlorovinylcysteine (DCVC), the key metabolite of the nephrotoxic and nephrocarcinogenic chemicals, trichloroethylene and dichloroacetylene, exerts potent acute cellular toxicity in LLC-PK1 cells (Vamvakas S., Bittner, D., Dekant, W. and Anders, M.W. (1992). Events that precede and that follow S-(1,2-dichlorovinyl)-L-cysteine-induced release of mitochondrial Ca2+ and their association with cytotoxicity to renal cells. Biochem. Pharmacol. 44, 1131-1138). In the present study we investigated whether long-term exposure of LLC-PK1 cells to low, non-cytotoxic concentrations of DCVC results in stable morphological and biochemical dedifferentiation. After 7 weeks exposure to 1 and 5 microM DCVC, morphologically changed single cells were picked under the microscope and cultured in absence of DCVC for 4-8 weeks. In contrast to the physiological cuboidal shape of untreated LLC-PK1 cells, the clones derived from long-term exposure to DCVC consisted of elongated, spindle-shaped cells tending to form irregular borders. Moreover, glucose uptake, pH-dependent ammonia production and dome formation, important indicators of the renal tubule origin of the LLC-PK1 cells, were severely impaired in the clones. In addition to the loss of membrane polarity, the clones exhibited altered composition of the nuclear matrix and intermediate filament proteins by two-dimensional gel electrophoresis, increased poly(ADP-ribosyl)ation of nuclear proteins and enhanced expression of c-fos. The induction of dedifferentiated LLC-PK1 clones with stable characteristics upon long-term exposure to the nephrocarcinogen DCVC may represent a useful in vitro model to study biochemical alterations involved in chronic renal toxicity and carcinogenicity.

Structure-mutagenicity and structure-cytotoxicity studies on bromine-containing cysteine S-conjugates and related compounds.

Glutathione and cysteine S-conjugates of several haloalkenes are nephrotoxic and cytotoxic. Chloroalkene-derived S-(1-chloroalkenyl)-L-cysteine conjugates, but not fluoroalkene-derived S-(2,2-dihalo-1,1-difluorethyl)-L-cysteine conjugates, are mutagenic in the Ames test, although both types of S-conjugates are cytotoxic and nephrotoxic. Recent studies showed that bromine-containing S-(2,2-dihalo-1,1-difluoroethyl)-L-cysteine conjugates are mutagenic in the Ames test, thus challenging the generalization that S-(2,2-dihalo-1,1-difluoroethyl)-L-cysteine conjugates are not mutagenic. Hence a series of bromine-containing and bromine-lacking S-(2,2-dihalo-1,1-difluoroethyl)-L-cysteine conjugates was prepared, and their mutagenicity was assessed in the Ames test with Salmonella typhimurium TA2638 as the test strain. In addition, several indices of cytotoxicity, including cytotoxicity in LLC-PK1 cells, induction of Ca2+ release from pig kidney mitochondria, and DNA double-strand breaks in LLC-PK1 cells, were measured. The bromine-containing S-conjugates S-(2-bromo-2-chloro-1,1-difluoroethyl)-L- cysteine (BCD-FC), S-(2-bromo-1,1,2-trifluoroethyl)-L-cysteine (BTFC), and S-(2,2-dibromo-1,1-difluoroethyl)-L-cysteine (DBDFC) were mutagenic in the Ames test, whereas S-(2-chloro-1,1,2-trifluorethyl)-L-cysteine (CTFC), S-(2,2-dichloro-1,1-difluoroethyl)-L-cysteine (DCDFC), and S-(1,1,2,2-tetrafluoroethyl)-L-cysteine (TFC), which lack bromine, were not. BCDFC, BTFC, CTFC, DBDFC, and TFC were cytotoxic in LLC-PK1 cells, and their cytotoxicity was blocked by the cysteine conjugate beta-lyase inhibitor (aminooxy)acetic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnetic resonance contrast agents in neuroimaging. New agents and applications.

Of the four gadolinium chelates in clinical use worldwide, only three are available in the United States: gadoteridol, gadodiamide, and gadopentetate dimeglumine. Although gadopentetate dimeglumine is still administered in many clinical practices, a consequence of being the first agent developed (1988) and until recently the only agent available, gadoteridol demonstrates a higher index of safety--at least on theoretical grounds. With linear chelates such as gadopentetate dimeglumine and gadodiamide, greater release of free gadolinium ion occurs in vivo owing to lower thermodynamic and kinetic stability. The concern with respect to demetallation and resultant increased chronic deposition of gadolinium ion in marrow and liver is greater with gadodiamide. Drug safety appears not to be an issue at high dose for gadoteridol, the only agent approved in this regards. The safety of the other chelates at high dose has yet to be established. The nonionic character of the two newer agents (gadoteridol and gadodiamide) is not of great importance in current clinical practice, in which most examinations are still performed with a dose of 0.1 mmol/kg given as a slow infusion. The non-ionic nature of the newer MR contrast agents may become clinically important in the future, with more common application of bolus injection and high dose. High contrast dose (0.3 mmol/kg) is advocated in routine MR clinical practice for the evaluation of intracranial metastatic disease. Only with prior evidence for multiple metastases and in patients for whom the detection of additional lesions would not influence therapy can the use of standard dose (0.1 mmol/kg) be justified.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of oxidative DNA modifications in mitochondria.

Specific repair endonucleases were used to quantify oxidative modifications in mitochondrial DNA (mtDNA) from rat liver and from porcine liver and kidney by means of a relaxation assay. In rat liver mitochondria the number of modifications sensitive to formamidopyrimidine--DNA glycosylase (FPG protein), which include 8-hydroxyguanine (8-oxo-7,8-dihydroguanine) residues, was only 0.8 +/- 0.2 per 10(5) base pairs (bp). Even lower values were observed in porcine kidney (0.5 +/- 0.3 per 10(5) bp) and liver (0.4 +/- 0.2 per 10(5) bp). The numbers of sites of base loss (AP sites) sensitive to T4 endonuclease V and of 5,6-dihydropyrimidines sensitive to endonuclease III were less than 0.2 per 10(5) bp in all cases. The data provide evidence that the steady-state levels of oxidative mtDNA modifications are low under physiological conditions, either because reactive oxygen species generated in the mitochondria are instantly inactivated or because of efficient DNA repair processes inside mitochondria.