Attosecond-Angstrom free-electron-laser towards the cold beam limit

Electron beam quality is paramount for X-ray pulse production in free-electron-lasers (FELs). State-of-the-art linear accelerators (linacs) can deliver multi-GeV electron beams with sufficient quality for hard X-ray-FELs, albeit requiring km-scale setups, whereas plasma-based accelerators can produce multi-GeV electron beams on metre-scale distances, and begin to reach beam qualities sufficient for EUV FELs. Here we show, that electron beams from plasma photocathodes many orders of magnitude brighter than state-of-the-art can be generated in plasma wakefield accelerators (PWFAs), and then extracted, captured, transported and injected into undulators without significant quality loss. These ultrabright, sub-femtosecond electron beams can drive hard X-FELs near the cold beam limit to generate coherent X-ray pulses of attosecond-Angstrom class, reaching saturation after only 10 metres of undulator. This plasma-X-FEL opens pathways for advanced photon science capabilities, such as unperturbed observation of electronic motion inside atoms at their natural time and length scale, and towards higher photon energies.

Hybrid LWFA-PWFA staging as a beam energy and brightness transformer: conceptual design and simulations

We present a conceptual design for a hybrid laser-driven plasma wakefield accelerator (LWFA) to beam-driven plasma wakefield accelerator (PWFA). In this set-up, the output beams from an LWFA stage are used as input beams of a new PWFA stage. In the PWFA stage, a new witness beam of largely increased quality can be produced and accelerated to higher energies. The feasibility and the potential of this concept is shown through exemplary particle-in-cell simulations. In addition, preliminary simulation results for a proof-of-concept experiment in Helmholtz-Zentrum Dresden-Rossendorf (Germany) are shown. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

Advanced schemes for underdense plasma photocathode wakefield accelerators: pathways towards ultrahigh brightness electron beams

The 'Trojan Horse' underdense plasma photocathode scheme applied to electron beam-driven plasma wakefield acceleration has opened up a path which promises high controllability and tunability and to reach extremely good quality as regards emittance and five-dimensional beam brightness. This combination has the potential to improve the state-of-the-art in accelerator technology significantly. In this paper, we review the basic concepts of the Trojan Horse scheme and present advanced methods for tailoring both the injector laser pulses and the witness electron bunches and combine them with the Trojan Horse scheme. These new approaches will further enhance the beam qualities, such as transverse emittance and longitudinal energy spread, and may allow, for the first time, to produce ultrahigh six-dimensional brightness electron bunches, which is a necessary requirement for driving advanced radiation sources. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

Experimental Determination of the Vapor Phase Thermal Conductivity of Blowing Agents for Polyurethane Rigid Foam

Blowing agents are mainly responsible for the insulation properties of polyurethane rigid foams. Detailed knowledge about the vapor conductivity of blowing agents and their mixtures is essential for their basic understanding. In addition to their insulation properties, blowing agents to a large extent determine the mechanical properties of the foam. Today, blowing agent mixtures are often used in an attempt to combine both worlds, low thermal conductivity and high vapor pressure at low temperatures. Our investigations aim at a better understanding of the relevant practical properties of blowing agents and their mixtures and to focus on their meaning for actual and potential foam systems of interest to the rigid foam insulation market.

A newly developed transient hot wire method was used to determine the vapor phase thermal conductivity of various blowing agents used in rigid polyurethane foam. Data for CFC-11, HCFC-141b, HFC-365mfc, HFC-356mffm, HFC-245fa, HFC-245ca, cyclopentane, isopentane, n-pentane, isobutane, n-butane, and carbon dioxide have been generated. In addition to measurements of the pure compounds, current market mixtures of cyclopentane with low boiling hydrocarbons have been investigated. Experiments have been performed at pressures between 0.2 MPa and 1.5 MPa and temperatures between 298 K and 421 K.

Data2Dynamics: a modeling environment tailored to parameter estimation in dynamical systems

Modeling of dynamical systems using ordinary differential equations is a popular approach in the field of systems biology. Two of the most critical steps in this approach are to construct dynamical models of biochemical reaction networks for large datasets and complex experimental conditions and to perform efficient and reliable parameter estimation for model fitting. We present a modeling environment for MATLAB that pioneers these challenges. The numerically expensive parts of the calculations such as the solving of the differential equations and of the associated sensitivity system are parallelized and automatically compiled into efficient C code. A variety of parameter estimation algorithms as well as frequentist and Bayesian methods for uncertainty analysis have been implemented and used on a range of applications that lead to publications.

AVAILABILITY AND IMPLEMENTATION

The Data2Dynamics modeling environment is MATLAB based, open source and freely available at http://www.data2dynamics.org.

CONTACT

andreas.raue@fdm.uni-freiburg.de

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Large-scale magnetic field generation by randomly forced shearing waves

A rigorous theory for the generation of a large-scale magnetic field by random nonhelically forced motions of a conducting fluid combined with a linear shear is presented in the analytically tractable limit of low magnetic Reynolds number (Rm) and weak shear. The dynamo is kinematic and due to fluctuations in the net (volume-averaged) electromotive force. This is a minimal proof-of-concept quasilinear calculation aiming to put the shear dynamo, a new effect recently found in numerical experiments, on a firm theoretical footing. Numerically observed scalings of the wave number and growth rate of the fastest-growing mode, previously not understood, are derived analytically. The simplicity of the model suggests that shear dynamo action may be a generic property of sheared magnetohydrodynamic turbulence.

[Ethical aspects of deep brain stimulation in the treatment of psychiatric disorders]

Deep brain stimulation (DBS) is currently being tested as a possible treatment for treatment-refractory psychiatric disorders. Besides the hope set on this new therapeutic approach of DBS, there are at the same time doubts concerning the ethical acceptability in the treatment of individuals suffering from mental disorders. Taking the therapeutic benefit of DBS into account, the manuscript analyses ethical aspects of DBS application in psychiatry. In particular, possible effects on the patient's personality and self-determination are scrutinized. It is shown that personality changes may either occur as unintended and potentially ethically troublesome side effects or may even be intended as legitimate therapy goals. The patient's self-determination may be both, endangered and supported by DBS. The ethical assessment of DBS considers therapeutic benefits, the method's minimal invasiveness and reversibility on the one hand, as well as surgery-related risks of DBS treatment, an insufficient data-base due to currently missing long-term studies and the possibility of as yet inestimable, potentially long-term effects on the patient's personality and self-determination on the other hand. The ethical balancing arrives at the conclusion that DBS may be considered as ultima ratio in the treatment of psychiatric disorders and should preferably be combined with psychosocial measures. Furthermore, a prospective scientific evaluation of the procedure should include a systematic investigation of personality changes.

Generation of magnetic field by combined action of turbulence and shear

The feasibility of a mean-field dynamo in nonhelical turbulence with a superimposed linear shear is studied numerically in elongated shearing boxes. Exponential growth of the magnetic field at scales much larger than the outer scale of the turbulence is found. The characteristic scale of the field is lB proportional S(-1/2) and the growth rate is gamma proportional S, where S is the shearing rate. This newly discovered shear dynamo effect potentially represents a very generic mechanism for generating large-scale magnetic fields in a broad class of astrophysical systems with spatially coherent mean flows.

Nonlinear growth of firehose and mirror fluctuations in astrophysical plasmas

In turbulent high-beta astrophysical plasmas (exemplified by the galaxy cluster plasmas), pressure-anisotropy-driven firehose and mirror fluctuations grow nonlinearly to large amplitudes, deltaB/B approximately 1, on a time scale comparable to the turnover time of the turbulent motions. The principle of their nonlinear evolution is to generate secularly growing small-scale magnetic fluctuations that on average cancel the temporal change in the large-scale magnetic field responsible for the pressure anisotropies. The presence of small-scale magnetic fluctuations may dramatically affect the transport properties and, thereby, the large-scale dynamics of the high-beta astrophysical plasmas.

Antibody targeting of TIRC7 results in significant therapeutic effects on collagen-induced arthritis in mice

TIRC7 is a cell surface molecule which is expressed in T and B lymphocytes and negatively regulates their function. Anti-TIRC7 specific monoclonal antibody (mAb) inhibited T cell memory response to recall antigens. Up-regulation of TIRC7 on lymphocytes from joint tissue of patients with Rheumatoid Arthritis (RA) and mice with collagen induced arthritis (CIA) suggested TIRC7 as a novel target to promote anti-inflammatory reaction. Anti-TIRC7 mAb administration significantly inhibited the induction and progression of CIA and the anti-collagen IgG1 and IgG2a antibody response. Combination therapy of anti-TIRC7 mAb and soluble TNF-alpha receptor demonstrated an increased inhibitory effect over the single compounds on CIA. The results demonstrate the therapeutic potential of TIRC7 targeting with mAb in diseases associated with exaggerated T and B cell responses.

Sleep disorders are long-term sequelae of both bacterial and viral meningitis

BACKGROUND

Many bacterial meningitis patients experience neurological or neuropsychological sequelae, predominantly deficits in short-term memory, learning, and attention. Neuropsychological symptoms after viral meningitis are observed less frequently. Sleep disturbance has been reported after both viral and bacterial meningitis.

OBJECTIVES

To examine systematically the frequency and extent of sleep disturbance in meningitis patients.

METHODS

Eighty six viral or bacterial meningitis (onset of acute disease at least 1 year previously) patients were examined using two standardised questionnaires (Schlaffragebogen B and the Pittsburgh Sleep Quality Index, PSQI) in conjunction with a standardised neurological examination, and compared to a control group of 42 healthy age-matched volunteers.

RESULTS

Patients after both viral and bacterial meningitis described their sleep as reduced in quality and less restful than that of healthy control subjects; both patient groups had a pathological mean PSQI total score. Impaired sleep scores after meningitis were not correlated to either the Glasgow Coma Scale or the Glasgow Outcome Scale. Moreover, no relationship between residual neurological dysfunction or depressivity and sleep quality was observed.

CONCLUSIONS

Impaired sleep is a long-term consequence of meningitis. Additional, so far undetermined, factors other than the severity of concomitant neurological deficits are responsible for the development of this sequela.

The dopamine receptor agonist lisuride attenuates iron-mediated dopaminergic neurodegeneration

Many dopamine agonists used in the treatment of Parkinson's disease are suggested to be potentially neuroprotective. On the basis of its structure, the dopamine agonist lisuride may share this characteristic. In the current study discrete asymptomatic lesions were produced by the injection of iron-laden neuromelanin into the rat substantia nigra and the animals treated with lisuride to determine the protective potential of this substance. Two treatment regimes were utilised. In the neuroprotective protocol, animals were treated with 0.1 mg.kg(-1) lisuride twice daily 3 days prior to, and 7 days following, the iron lesion. In the neurorescue protocol, the animals received 0.1 mg.kg(-1) lisuride twice daily for 1 week beginning on the fourth day post surgery. Eight weeks post surgery, tyrosine hydroxylase-positive neurons surrounding the injection site (33% of total nigral volume) were counted. Dopamine neuron number in iron-lesioned animals was reduced to 50% of that in vehicle-injected animals. The absence of motoric disturbances or a striatal dopamine deficit in these animals suggests a subclinical dopaminergic lesion. Dopamine neuron number in the quantified area in sham-injected animals receiving lisuride or iron-lesioned animals receiving lisuride in both the neuroprotection and neurorescue groups were not significantly reduced. These results suggest that lisuride can protect neurons against iron-induced cell death and might thus be neuroprotective in Parkinson's disease.

Relationships between various behavioural abnormalities and nigrostriatal dopamine depletion in the unilateral 6-OHDA-lesioned rat

While rotational asymmetry is used as a characteristic behavioural sign of striatal dopamine (DA) loss in unilateral animal models of Parkinson's disease (PD), there is relatively little analysis of how other common behavioural deficits relate to nigrostriatal DA depletion. We analysed the relationships between several deficits induced by unilateral 6-OHDA lesions and striatal neurochemistry, as well as neuronal loss in the dopaminergic substantia nigra (SN). Behaviour was evaluated from before until 6 weeks after surgery and abnormalities appeared in body axis, head position and sensorimotor performance as well as apomorphine-induced rotation. As expected, rotational behaviour correlated with striatal DA loss and not with other striatal neurotransmitters measured. Similar observations were found for sensorimotor deficits ('disengage task'). Both deficits were observed in rats with >70% loss of TH+ nigral neurons and >80% loss of striatal DA. Additional postural abnormalities appeared with mean losses of 87% of nigral DA neurons and 97% striatal DA, consistent with observations in patients with advanced PD. The data show that the repertoire of behavioural abnormalities manifested by hemiparkinsonian rats relate directly to the degree of nigrostriatal DA loss and, therefore, mimic features of PD. Analysis of such behaviours are relevant for chronic therapeutic studies targeting PD.

[Possibilities and limits of harvesting and using human embryonic stem cells]

The availability of human embryonic stem cells as well as recent results about tissue specific stem cells residing in various organs of the human body have provided novel tools for basic sciences and medicine, which may result in a substantial increase of knowledge and the development of novel therapeutic concepts for the treatment of presently incurable diseases. Stem cell technologies, however, also raise fundamental ethical problems related to the sourcing and use of the cells. On the basis of a description of cultured stem cells derived from human embryos (ES cells), aborted human fetuses (EG cells), and tissues of the adult organism, respectively, the present article analyses ethical problems specifically related to each of these procedures in the context of the ethical principles underlying German law.

The industrial chemical Tinuvin 123 does not induce dopaminergic neurotoxicity in C57Bl/6 mice

We have investigated the acute effects of systemic administration of Tinuvin 123 on nigro-striatal dopaminergic neurons in the C57Bl/6 mouse. Tinuvin 123 was administered subcutaneously (s.c.) twice, 16 h apart, at doses of 0, 2, 20 or 200 mg/kg body weight to a total of 48 male C57Bl/6 mice (12 animals/group). Seven days following the last dose the animals were decapitated and the brains removed. No deaths occurred during the study. There were no differences between the mean body weights of any of the experimental groups prior to or following Tinuvin 123 treatment. Animals treated s.c. with 2 mg/kg Tinuvin 123 exhibited no changes in striatal dopamine or metabolite concentrations compared with vehicle-treated animals. Higher doses of Tinuvin 123 (20 and 200 mg/kg) resulted in a moderate loss of striatal dopamine (31 and 38%) but concentrations of the dopamine metabolites 3,4-dihydroxyphenylacetic acid and homovanillic acid and the neurotransmitters serotonin, aspartate, gamma aminobutyric acid and glutamate were unchanged. The total number of tyrosine hydroxylase-immunoreactive neurons in the entire substantia nigra were equivalent in the vehicle- and Tinuvin 123-treated animals at all doses, thus no neuronal loss was demonstrated. In conclusion, this study demonstrates no evidence that systemic administered Tinuvin 123 induces dopaminergic neurotoxicity in C57Bl/6 mice.

Characterization and regional distribution of nitric oxide synthase in the human brain during normal ageing

Nitric oxide (NO) is a highly diffusible cellular mediator generated from L-arginine by the enzyme nitric oxide synthase (NOS). As little is known about the regional distribution of NOS in the human brain, we examined the distribution pattern of nitric oxide synthase activity in 28 regions of the human brain using the [(3)H]L-citrulline formation assay. To elucidate which isoforms contribute to the total NOS activity we performed Western blot analysis of neuronal, inducible and endothelial NOS. We further determined brain levels of arginine and citrulline as a potential index of NOS activity pre mortem. NOS activity appears to remain unaltered during ageing and is independent of post mortem delay, gender or sample storage time. We identified a regional pattern of NOS distribution with highest levels of NOS activity in the substantia innominata, cerebellar cortex, nucleus accumbens and subthalamicus, whereas lowest levels were measured in the corpus callosum, thalamus, occipital cortex, and dentate nucleus. nNOS was measured throughout the brain, in contrast iNOS and eNOS were not detectable. We therefore conclude that primarily nNOS is responsible for NOS activity in the human brain. Levels of citrulline were higher than those of arginine, but did not correlate with the enzyme activity, suggesting that these parameters are unsuitable for testing NOS activity premortem. The characterization and topographical pattern of NOS in the human brain during normal ageing may assist our understanding of the physiological role of NO and its relevance in Parkinson's and Alzheimer's disease, alcoholism, schizophrenia and AIDS.

Genomic organization of the gene coding for TIRC7, a novel membrane protein essential for T cell activation

A novel human membrane protein, TIRC7, was recently identified and demonstrated to be essential in T cell activation. Here we report on the genomic organization of the TIRC7 gene, which is composed of 15 exons and spans 7.9 kb. The seven predicted transmembrane-spanning domains of the TIRC7 protein coincide well with exon-intron boundaries. TIRC7 and OC116, a recently described putative subunit of the vacuolar proton pump that was demonstrated to be expressed in an osteoclastoma tumor as well as in a human pancreatic adenocarcinoma cell line, are demonstrated to be alternative transcripts of the same gene. OC116 consists of 20 exons with the last 14 introns and exons being identical with those of TIRC7. The chromosomal locus for both transcripts was identified on chromosome 11q13.4-q13.5. In human alloactivated T lymphocytes, mRNA expression of TIRC7, but not OC116, is demonstrated, indicating that OC116 is not involved in regular T cell proliferation.

The human homolog of Drosophila cornichon protein is differentially expressed in alloactivated T-cells

To identify novel genes induced in the early stage of T-cell activation, mRNA expression in alloactivated human lymphocytes was examined. Differential display-reverse transcription PCR analysis revealed a 207-bp cDNA fragment which was upregulated 24 h after allostimulation of a human T-cell line. The corresponding complete 1396 bp cDNA, named TGAM77, encodes a predicted 134 amino acid protein which shares 63% homology with the cornichon (cni) protein of Drosophila melanogaster. Upregulation of TGAM77 mRNA in the early phase of T-cell activation was confirmed by Northern blot and RT-PCR analysis of activated human lymphocytes. TGAM77 mRNA is expressed in a variety of human tissues with various expression levels. In analogy to cni which is involved in an epidermal growth factor-like signaling pathway inducing cellular asymmetry in Drosophila oogenesis, TGAM77 might function in similar signaling establishing vectorial re-localization and concentration of signaling events in T-cell activation.

Involvement of microglia in cerebrospinal fluid glutamate increase in SIV-infected rhesus monkeys (Macaca mulatta)

Cerebrospinal fluid (CSF) samples were collected from 24 uninfected and 24 SIV251 MPBMC-infected rhesus monkeys during early infection and from 6 animals in a longitudinal design up to 7 months postinfection to investigate excitatory and inhibitory amino acid neurotransmitter levels. During the early infection period CSF amino acid concentrations of infected animals were not significantly different from those of uninfected animals. However, long-term studies demonstrated that gamma-aminobutyric acid (GABA) concentrations were decreased while glutamate concentrations were increased late in infection compared with the preinfection values of the same animals. Moreover, we showed that the source of increased glutamate in animals with AIDS is, at least partially, microglial cells. Our data support the hypothesis that excitotoxicity is involved in immunodeficiency virus-induced neurological disease and propose microglia as a contributor to excitotoxic damage.

U-shape relationship between change in dietary cholesterol absorption and plasma lipoprotein responsiveness and evidence for extreme interindividual variation in dietary cholesterol absorption in humans

A possible relationship between change in dietary cholesterol absorption and plasma lipoprotein responsiveness was examined in 18 normal subjects fed low fat low cholesterol, high fat low cholesterol, and high fat high cholesterol diets. For the group, neither dietary cholesterol nor dietary fat affected the percentage dietary cholesterol absorption, whereas dietary cholesterol intake raised total and LDL-C and dietary fat raised total, LDL, and HDL-C. On a fixed diet there was approximately a 2-fold variation among subjects in percentage dietary cholesterol absorption. Subjects also varied in response to dietary cholesterol and fat with regard to dietary cholesterol absorption and plasma lipoprotein responsiveness. There was a U-shaped parabolic relationship between dietary cholesterol-induced percent change in LDL-C and the change in percentage dietary cholesterol absorption (R2 = 0.62, P = 0.005). A similar but weaker relationship characterized the responsiveness of HDL-C (R2 = 0.38, P = 0.05). For the group, increased cholesterol intake raised dietary cholesterol mass absorption from 1.6 to 4.6 mg/kg per day, but the range of increase was from 1 to 4.7 mg/kg per day. Increased fat intake also affected dietary cholesterol mass absorption with most subjects displaying a strong inverse relationship between fat intake and mass absorption (r = -0.77, P < 0.003). In summary: i) the percentage change in dietary cholesterol absorption in response to dietary cholesterol does appear to regulate diet responsiveness of LDL and HDL-C, and ii) the large variability in percent absorption and changes in percentage and mass absorption in response to dietary cholesterol suggest the presence of genetically determined differences among individuals in the regulation of dietary cholesterol absorption.

Prevention of acute allograft rejection by antibody targeting of TIRC7, a novel T cell membrane protein

A novel 75 kDa membrane protein, TIRC7, is described that exhibits a central role in T cell activation in vitro and in vivo. Modulation of TIRC7-mediated signals with specific anti-TIRC7 antibodies in vitro efficiently prevents human T cell proliferation and IL-2 secretion. Moreover, anti-TIRC7 antibodies specifically inhibit type 1 subset specific IFN-gamma expression but spare the type 2 cytokine IL-4. Diminished proliferation but not IFN-gamma secretion is reversible by exogenous rIL-2. An anti-TIRC7 antibody that cross-reacts with the 75 kDa rat homolog exhibits inhibition of rat alloimmune response in vitro and significantly prolongs kidney allograft survival in vivo. Targeting of TIRC7 may provide a novel therapeutic approach for modulation of the immune response.

Phosphorylated cis-4-methylsphingosine mimics the mitogenic effect of sphingosine-1-phosphate in Swiss 3T3 fibroblasts

The phosphorylated derivative of sphingosine, sphingosine-1-phosphate, is a short-living metabolite of ultimate ceramide degradation and was shown to act as an intracellular signaling molecule, stimulating cell proliferation in quiescent Swiss 3T3 fibroblasts and inducing the release of calcium from intracellular stores (Zhang, H., Desai, N. N., Olivera, A., Seki, T., Brooker, G., and Spiegel, S. (1991) J. Cell. Biol. 114, 155-167). In the present study, 24-h treatment of Swiss 3T3 fibroblasts with the synthetic sphingosine analogue cis-4-methylsphingosine resulted in proliferation of quiescent Swiss 3T3 fibroblasts that was 3-fold stronger than that of equimolar sphingosine-1-phosphate. The phosphorylated derivative of cis-4-methylsphingosine accumulated drastically in the cells. Simultaneous treatment with the sphingosine kinase inhibitor L-threo-sphinganine reduced both the amount of phosphorylated cis-4-methylsphingosine and cell proliferation induced by this compound by about 50%, indicating that the phosphorylated derivative mediated the proliferative stimulus. The mitogenic effect of cis-4-methylsphingosine was associated with a mobilization of intracellular calcium in Swiss 3T3 fibroblasts that was similar to that induced by sphingosine-1-phosphate. The results demonstrate that the phosphorylated derivative of cis-4-methylsphingosine mimics the previously reported mitogenic action of sphingosine-1-phosphate in Swiss 3T3 cells, and the stronger effect most likely corresponds to the unusual accumulation of this compound.

Turnover of endogenous ceramide in cultured normal and Farber fibroblasts

De novo synthesis and turnover of endogenous ceramide in cultured skin fibroblasts from patients affected with Farber lipogranulomatosis were studied by biosynthetical labeling of cellular sphingolipids with [14C]serine. The cellular uptake of [14C]serine and incorporation into de novo synthesized ceramide was similar in normal and Farber fibroblasts, with a half life of newly synthesized ceramide of 2.7 h in normal and diseased cells. Newly synthesized ceramide was found to be channeled directly into biosynthesis of complex sphingolipids rather than contributing to the pool of accumulated ceramide in Farber fibroblasts. The degradation of ceramide generated by the catabolism of complex sphingolipids in Farber cells was greatly delayed compared with control fibroblasts, with differences in the amount of radiolabeled cellular ceramide becoming evident after 6 h chase time. Individual Farber cell lines differed from each other in the amount of accumulated ceramide; however, no correlation was found between ceramide accumulation and residual acid ceramidase activity as determined in vitro. In addition, the amount of radiolabeled sphingomyelin was significantly increased in Farber fibroblasts suggesting a delayed degradation of this compound in this ceramide storage disorder. We propose biosynthetical labeling of endogenous ceramide with [14C]serine, in addition to other established methods, as a highly sensitive and reliable method for the diagnosis of Farber disease, allowing semiquantitative measurement of ceramide accumulation in cultured skin fibroblasts of patients affected with Farber lipogranulomatosis.

cis-4-Methylsphingosine decreases sphingolipid biosynthesis by specifically interfering with serine palmitoyltransferase activity in primary cultured neurons

The effect of six different structurally modified sphingosine analogues on biosynthesis of sphingolipids was studied in primary cultured murine cerebellar neurons. Treatment of cells with cis-4-methylsphingosine at micromolar levels resulted in a markedly decreased sphingolipid biosynthesis, whereas the other compounds examined, trans-4-methylsphingosine, cis-5-methylsphingosine, trans-5-methylsphingosine, cis-sphingosine, and 1-deoxysphingosine, inhibited sphingolipid biosynthesis less efficiently. The inhibition of sphingolipid biosynthesis by the various compounds was paralleled by a decrease of serine palmitoyltransferase activity in situ. For cis-4-methylsphingosine the inhibitory effect on serine palmitoyltransferase activity was shown to be concentration- and time-dependent. Half-maximal reduction of enzyme activity occurred after 24 h of treatment with 10 microM of the compound. The activity of other enzymes of sphingolipid biosynthesis as well as phospholipid and protein biosynthesis was not affected. Analysis of the sphingoid moiety of cellular sphingolipids suggests that the sphingosine analogues listed above were subject to degradation rather than being utilized as precursors for sphingolipid biosynthesis by cultured neurons. Except of 1-deoxysphingosine, the other five sphingosine analogues were shown to be substrates for sphingosine kinase in vitro. After 24 h of treatment of primary cerebellar neurons with the various sphingosine analogues the relative percentage of the respective intracellular 1-phosphate derivatives paralleled exactly the inhibitory effect on serine palmitoyltransferase activity observed when cells were treated with the unphosphorylated compounds. In contrast to the respective 1-phosphate derivatives of the other methyl-branched sphingosine analogues examined, cis-4-methylsphingosine 1-phosphate showed an intracellular accumulation suggesting a delayed turnover rate in cultured murine neurons for this compound. These results suggest that the inhibitory effect of the sphingosine analogues on serine palmitoyltransferase is mediated by their respective 1-phosphate derivatives and that the pronounced effect of cis-4-methylsphingosine is caused by a high intracellular concentration of cis-4-methylsphingosine 1-phosphate. cis-4-Methylsphingosine, in addition, caused drastic changes in cell morphology of primary cerebellar neurons, which were not observed when these cells were treated with one of the other sphingosine analogues examined.

Alternative polyadenylation of apolipoprotein B RNA is a major cause of B-48 protein formation in rat hepatoma cell lines transfected with human apoB-100 minigenes

The human apoB gene encodes an mRNA of 14121 nucleotides. In liver the apoB gene products a full-length mature protein of 4,536 amino acids (B-100), whereas in the intestine this gene produces a truncated protein of 2,152 amino acids (B-48). B-48 results from RNA editing of nucleotide 6666 from C to U, thereby producing a stop codon at position 2153. Rat liver has been shown to contain apoB RNA editing capability resulting in production of both B-100 and B-48. To create an in vitro expression system for human B-100, a minigene with a wild type coding sequence for the entire B-100 protein (B-100/Gln) was stably transfected into rat hepatoma cells (McA-RH7777). Similarly, a minigene with mutation at nucleotide 6667 that allowed translation even after editing of nucleotide 6666 (B-100/Leu, nonstop mutant), a minigene with an additional nonsense mutation at nucleotide 7053 to produce B-50 (B-50/Leu), and a truncated wild type minigene with a stop signal at codon 3261 to produce B-74 and an mRNA of 10 kb (B-74/Gln) were also transfected. Very little full-length B-100 and B-74 was produced by any of the respective constructions, including the B-100/Leu with the nonstop mutation. Transfection with B-100/Gln, B-100/Leu and B-74/Gln constructions produced greater than 90% of apoB as B-48, whereas the B-50/Leu construction produced 76% B-50 and 24% B-48. The inability of the B-100/Leu construction to produce B-100 suggested an explanation for B-48 production other than RNA editing. Northern blot analysis showed that the RNA produced by all four transfectants was shortened to a size of about 7 kb. A 10-kb but no 7-kb RNA was observed in the B-74/Leu construction when transfected to Chinese hamster ovary cells suggesting cell type specificity in generation of a shortened RNA. The 3' end of apoB RNA from McA-RH7777 B-100/Leu transfectants was reverse transcribed, cloned, and sequenced. This revealed two species of RNA: one polyadenylated at or near nucleotide 6775 capable of coding for B-48, the other polyadenylated at nucleotide 7080 capable of coding for B-50. In 18% of the cDNA clones, nucleotide 6666 was edited from C to T. In 6 of 34 clones, addition of the poly(A) tail after nucleotide 6774 created a TAA stop codon, whereas no stop signals could be detected in the remaining clones.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of intestinal absorption of cholesterol with different plant sterols in man

Intestinal absorption of cholesterol, campesterol, campestanol, stigmasterol and sitosterol were measured in 10 healthy subjects by an intestinal perfusion technique over a 50 cm segment of the upper jejunum using sitostanol as non-absorbable marker. Cholesterol absorption was highest and averaged 33%., whereas the absorption rate of sitosterol averaged 4.2% and of stigmasterol 4.8%. Higher absorption rates were found for campesterol (9.6%). Campestanol, the 5 alpha saturated derivative of campesterol, showed the highest absorption rate (12.5%) of all plant sterols. A positive correlation between the absorption rate of cholesterol and campesterol was established. In addition, there was a negative correlation between the ratio of sitosterol to cholesterol and the mass of cholesterol absorption. These results are in agreement with previous observations in animal studies, namely, that increasing the length of the side-chain of cholesterol decreases the absorbability of the sterol. Surprisingly, campestanol, the 5 alpha saturated derivate of campesterol, was shown to have higher absorbability compared with its unsaturated compound. This finding is in contrast to previous assumptions, that hydrogenisation of the nucleus double bond of a sterol causes a decrease of absorbability, as has been demonstrated for cholesterol/cholestanol and sitosterol/sitostanol.

Effect of low-dose sitostanol on serum cholesterol in patients with hypercholesterolemia

Sitostanol (24-ethyl-5 alpha-cholestan-3 beta-ol), a hydrogenated derivative of sitosterol, was administered in a low dose (1.5 g/day) for 4 weeks to 6 patients with hypercholesterolemia. Total cholesterol was reduced significantly after 3 and 4 weeks by 10 and 15%, respectively. The reduction of total cholesterol was entirely due to a fall in LDL cholesterol. Total triglycerides and HDL cholesterol were not altered. Two weeks after cessation of sitostanol administration serum cholesterol returned to pretreatment levels. No significant amounts of sitostanol could be detected in plasma during therapy. These results suggest that low-dose sitostanol might be a useful hypolipidemic agent for the treatment of mild hypercholesterolemia.

[Anesthesia in aortocoronary bypass surgery: comparison of effects on hemodynamics of recent technics of total intravenous anesthesia]

20 patients electively scheduled for operation were enrolled in the study and anaesthetized randomly with one of the two techniques etomidate + fentanyl (I) or flunitrazepam + fentanyl (II). Haemodynamics were assessed by continuously measuring blood pressure in the systemic and pulmonary circulations, as well as the heart rate, and intermittently determining the cardiac output. It could be shown that systemic arterial blood pressure, in spite of an initial drop after induction of anaesthesia, remained within an acceptable safety margin throughout the investigation period. Whereas heart rate remained almost constant in both groups, the rate-pressure product which may serve as a measure of myocardial oxygen consumption in the clinical setting, decreased considerably in both groups, although more appreciably under the influence of the anaesthetic technique flunitrazepam + fentanyl. Although the diastolic blood pressure as the most significant individual factor determining coronary blood flow was not changed appreciably in both groups, it remained at a higher level under the influence of the anaesthetic technique etomidate + fentanyl (I). We conclude that both anaesthetic regimes described here may be safely applied for the anaesthesia of patients with reduced coronary perfusion and cardio-haemodynamic reserve potential.