2,076 research outputs found
Evaluation of the hCMEC/D3 cell line, a new "in vitro" model of the human blood-brain barrier for transport and gene regulation studies
No full textBrain endothelial capillary cells form the blood-brain barrier (BBB), a highly selective
membrane between the peripheral blood and the central nervous system. The main
functions of the BBB are to protect the brain tissue by preventing the entry of toxic
compounds and to supply it with nutrients in order to assure proper function. Tight
junctions are the key elements for the establishment of a tight barrier and seal the
intercellular gaps against passive diffusion of hydrophilic compounds. A second important
characteristic of the brain capillary endothelial cells are transport proteins that prevent
brain penetration of their substrates by pumping them back in the blood. These
compounds include a series of clinically used drugs. Important drug efflux transporters
located at the BBB are P-glycoprotein (P-gp), the breast cancer resistance protein
(BCRP) and the family of multidrug resistance proteins (MRP).
During drug development, the question of whether a drug candidate reaches the brain
tissue is of great importance. Therefore, models are needed to predict the BBB
permeability of new compounds. In the past, in vitro models have been developed to
address this question. These models include isolated brain capillaries, isolated primary
brain capillary endothelial cells and BBB cell lines of various origins. A major problem
encountered with these cell lines was an insufficient paracellular resistance.
Recently, the hCMEC/D3 cell line was generated by immortalizing primary human brain
endothelial cells. In culture this cell line shows a morphology that closely resembles to
primary cells, forms tight monolayers and expresses BBB markers such as chemokine
receptors, tight junctional molecules and ATP binding cassette (ABC)-transporters.
The aim of this thesis was to evaluate the hCMEC/D3 cell line as an in vitro model of the
human BBB to study 1) permeability properties including para- and transcellular diffusion
as well as active transport 2) the influence of endo- and exogenous factors on the
paracellular permeability and 3) the regulation of breast cancer resistance protein and Pglycoprotein
by pro-inflammatory cytokines.
The first study describes the characterization of the hCMEC/D3 cells as an in vitro model
of the human BBB for permeability studies (section Error! Reference source not
found.). The ability of the cells to allow discrimination between para- and transcellular
diffusion was investigated by measuring the transport of a series of compounds with
different physicochemical properties. A ratio of 2.8 was observed when comparing the
permeabilities of the compounds with the highest and the lowest diffusion rate. The
passive permeability of sucrose could be reduced significantly by replacing fetal calf
serum with human serum. Furthermore, quantitative mRNA expression of the ABCtransporters
P-gp, BCRP, MRP1, MRP2, MRP3, MRP4, MRP5 as well as the human
transferrin receptor (hTfR) was shown. Protein expression of P-gp, BCRP and the hTfR
was detected and functional activity of P-gp, BCRP and the MRPs was investigated in
efflux experiments. Furthermore, bidirectional P-gp transport activity was observed.
In a second project the impact of endo- and exogenous factors on the paracellular
permeability of hCMEC/D3 monolayers was assessed, since it is know that the molecular
assembly of tight junctions depends on the surrounding milieu (section Error! Reference
source not found.). Based on reports in the literature, the cells were incubated with a
variety of compounds that included anti-inflammatory drugs, growth factors and
antioxidants. The effects on the monolayer tightness of hCMEC/D3 were investigated by
measuring the transport of sucrose, a paracellular permeability marker. N-acetylcystein
(NAC), atorvastatin and sodium nitroprusside (SNP) reduced the sucrose permeability
significantly, and slightly increased zonula occludens protein (ZO-1) expression.
Additionally, NAC and SNP reduced the generation of reactive oxygen species (ROS),
which have been reported to disrupt the assembly of tight junctions.
The effect of the pro-inflammatory cytokines IL-1[beta], IL-6 and TNF-[alpha] on the expression and
activity of the ABC-transporters BCRP and P-gp was investigated in the hCMEC/D3 cell
line (section Error! Reference source not found.). IL-1[beta], IL-6 and TNF-[alpha], which are
know to be elevated during various diseases, suppressed significantly BCRP mRNA
expression. In addition, BCRP activity was reduced under the influence of all tested
cytokines, as shown by efflux experiments. P-gp mRNA levels were slightly reduced by
IL-6 but significantly increased after TNF-[alpha] treatment. TNF-[alpha] also increased the protein
expression of P-gp. This in vitro study indicates that expression levels of BCRP and P-gp
at the BBB might be altered during acute or chronic inflammation, resulting in a changed
brain penetration of their substrates.
In an isolated project, the pharmacokinetics and pharmacodynamics of increasing oral
doses of the satiety peptides GLP-1 and PYY3-36 were assessed in healthy male
volunteers. Oral administration of either peptide induced a rapid and dose-dependent
increase in plasma drug concentrations. Oral administration of GLP-1 induced a potent
effect on insulin release and both peptides suppressed ghrelin secretion. In conclusion,
this study showed, for the first time, that satiety peptides such as GLP-1 and PYY3-36
can be orally delivered safely and effectively in humans
Zur Entstehung sozialer Ordnung im interindividuellen Umgang: dargestellt am Beispiel gegengeschlechtlicher Arrangements
No full textBirk M. Zur Entstehung sozialer Ordnung im interindividuellen Umgang: dargestellt am Beispiel gegengeschlechtlicher Arrangements. Bielefeld; 1988
Developments in plant breeding for improved nutritional quality of soya beans II. Anti-nutritional factors
No full textNutritional value of most plant materials is limited by the presence of numerous naturally occurring compounds which interfere with nutrient digestion and absorption. Although processing is employed widely in removal of these factors, selection of cultivars of soya beans with inherently low levels would have a considerable impact on efficiency of non-ruminant livestock production. The review considers the role of plant breeding in achieving this objective. The most abundant trypsin inhibitors are the Kunitz and the Bowman Birk inhibitors, containing 181 and 71 amino acids respectively. The Kunitz inhibitor is present at a concentration of 1.4g/kg of total seed contents and the Bowman Birk inhibitor 1.6g/kg. A large number of isoforms of the Bowman Birk inhibitor have been described in soya bean cultivars and it has been shown that the general properties of the inhibitor are, in fact, attributable to different isoforms. Nulls for both Bowman-Birk and Kunitz trypsin inhibitors have been identified, allowing new low trypsin inhibitor cultivars to be produced. However, research into breeding for low trypsin inhibitor cultivars currently has limited application as trypsin inhibitors contribute a major proportion of the methionine content of soya beans. Trypsin inhibitors are thought to be involved in the regulation of and protection against unwanted proteolysis in plant tissues and also act as a defense mechanism against attack from diseases, insects and animals. Hence, in breeding programes for low trypsin inhibitor cultivars, alternative protection for growing plants must be considered. Use of soya beans in non-ruminant animal feeds is limited by the flatulence associated with their consumption
Primary structure of Dioclea glabra trypsin inhibitor, DgTI, a Bowman-Birk inhibitor
No full textA novel serine proteinase inhibitor, DgTI, was purified from Dioclea glabra seeds by acetone precipitation, and ion-exchange and reverse phase chromatography. the inhibitor belongs to the Bowman-Birk family, and its primary sequence, determined by Edman degradation and mass spectrometry, of 67 amino acids is: SSGPCCDRCRCTKSEPPQCQCQDVRLNSC-HSACEACVCSHSMPGLCSCLDITHFCHEPCKSSGD- DED, Although two reactive sites were determined by susceptibility to trypsin (Lys(13) and His(40)), the inhibitory function was assigned only to the first site. the inhibitor forms a 1:1 complex with trypsin, and Ki is 0.5 x 10(-9) M. Elastase, chymotrypsin, kallikreins, factor Xa, thrombin, and plasmin were not inhibited. By its properties, DgTI is a Bowman-Birk inhibitor with structural and inhibitory properties between the class of Bowman-Birk type I (with a fully active second reactive site), and Bowman-Birk type II (devoid of second reactive site). (C) 1999 Academic Press.Universidade Federal de São Paulo, Escola Paulista Med, Dept Bioquim, BR-04044020 São Paulo, BrazilUniv Munich, Chirurg Klin & Poliklin, Klin Chem & Klin Biochem Abt, Munich, GermanyUniversidade Federal de São Paulo, Escola Paulista Med, Dept Bioquim, BR-04044020 São Paulo, BrazilWeb of Scienc
Identification of localised recharge and conduit flow by combined analysis of hydraulic and physico-chemical spring responses (Urenbrunnen, SW-Germany)
No full textKarst aquifers are highly vulnerable to contamination due to the rapid transport of pollutants in conduit systems. Effective strategies for the management and protection of karst aquifers, therefore, require an adequate hydrogeological characterisation of the conduit systems. In particular, the identification and characterisation of conduits transmitting rapid, localised recharge to springs is of great interest for vulnerability assessments. In this work, it is demonstrated that localised recharge and conduit flow in a karst aquifer (Urenbrunnen catchment, southwest Germany) can be characterised by jointly analysing the hydraulic and physico-chemical responses of a spring to recharge events. Conduit volumes are estimated by evaluating time lags between increases in spring discharge and associated changes in the electrical conductivity and temperature of the discharged water. These estimates are confirmed by the results of a combined tracer and recharge test. Variations in electrical conductivity are also shown to assist in the quantification of the fast recharge component associated with short-term recharge pulses. However, spectral analysis of temperature fluctuations reveals that highly mineralised surface waters locally infiltrate into the aquifer during the winter and spring without causing significant electrical conductivity variations in the spring water. Hence, the most consistent conceptual model is obtained by a combined analysis of both physico-chemical parameters. (C) 2003 Elsevier B.V. All rights reserved
Anticarcinogenic Bowman Birk Inhibitor from Snail Medic Seeds (Medicago scutellata): The 2.0 Å Crystal Structure of the Tertiary Complex with Bovine Trypsin
No full textAnticarcinogenic Bowman Birk Inhibitor from Snail Medic Seeds (Medicago scutellata): The 2.0 Å Crystal Structure of the Tertiary Complex with Bovine Trypsi
Tabu und Identität. Wie man das vermittelt, worüber die anderen schweigen
No full textMit einem Tabu werden Themenbereiche belegt, die sich im öffentlichen Raum einer Gesellschaft dem (sprachlichen) Zugriff aus moralischen, religiösen oder konventionellen Gründen entziehen. Tabubrüche werden daher als ein Angriff auf die Identität des Einzelnen oder seiner Gesellschaft wahrgenommen: Derjenige, der Tabubrüche begeht, respektiert die Privatsphäre des Individuums bzw. die Regeln des öffentlichen Raumes nicht und muss Sanktionen unterschiedlicher Art erfahren.
Wegen ihrer stabilisierenden Funktion für die Identität einer Gesellschaft stellen Tabus sensible Problembereiche innerhalb der interkulturellen Kommunikation dar, denn die Gefahr unbeabsichtigt Tabubrüche zu vollziehen, ist immer dann besonders groß, wenn Menschen unterschiedlicher Kulturen gemeinsam handeln sollen. Man denke dabei an Verhandlungen in Wirtschaft und Politik oder an den Aufbau von Firmenniederlassungen im Ausland, aber auch an die Integrationsarbeit mit Ausländern, an multikulturelle Gemeindearbeit sowie multinationale Kindergärten und Schulen.
Der moderne Fremdsprachenunterricht, der auch die interkulturelle Kompetenz fördern will, muss sich der Thematik annehmen. Geht es doch darum Kulturvermittler auszubilden, die der Internationalisierung der Arbeitswelt gewachsen sind und beruflich beispielsweise in Wirtschaft und Politik beratende Funktionen übernehmen oder als Dolmetscher sowie als Kulturberater im Krankenhaus, bei Gericht oder in der Familienberatung tätig sein können.
So bedeutsam das Thema Tabu für die Entwicklung der interkulturellen Kompetenz ist, so schwierig ist seine Behandlung im Unterricht, voll allem deshalb, weil es sich dem bewussten Zugriff entzieht. Soll das, was der öffentliche Raum einer fremden Kultur ausschließt, nicht lediglich durch oberflächliche Verhaltensregeln in Form einer To-do-Liste oder besser Not-to-do-Liste vermittelt, sondern im Rahmen eines Sensibilisierungsprozesses erarbeitet werden, so bedarf es der Annäherung und des Dialogs mit den anderen. Doch genau dies kann im Falle von Tabus nur rudimentär stattfinden. Die Vertreter der Fremdkultur müssten Themen ansprechen, über die sie eigentlich nicht reden, und Verhaltensweisen beschreiben, die in ihnen unangenehme Gefühle erregen. Dies gilt nicht zuletzt auch für uns selbst, die wir unsere eigenen Hürden diesbezüglich überwinden müssen.
Der Umgang mit den „heiklen Themen“ stellt daher ganz besondere Anforderungen an den Einzelnen. Diese wollen wir in unserem Vortrag an einigen Beispielen aus dem deutsch-italienischen Kontext darlegen, um dann exemplarisch zu zeigen, wie im Fremdsprachen- und Kulturunterricht Sensibilitäten gefördert werden können, die es den angehenden Kulturvermittlern erlauben, auf angemessene Weise mit den Tabus der anderen umzugehen. Um einen besseren Praxistransfer zu erreichen, werden den Zuhörern Übungen vorgestellt, die sie selbst ausprobieren, diskutieren und analysieren können
On Economic Cooling of Contained Server Racks using an Indirect Adiabatic Air Handler
No full textWe study the economic operation of a free-cooling setup in which an Indirect Adiabatic Air Handler (IAAH) recovers heat from an array of server racks placed in a contained aisle. For this setting we propose two different control policies: in the first approach, the airflow supply rate to the racks is maintained constant while only the process-side operations of the IAAH are optimized. In the second approach, also the room-side rate is updated adaptively. Building on calibrated models of the IAAH and the servers, we design experimental trials considering different outdoor temperatures and humidity conditions as well as varying computational workloads. The in silico analysis contributes actionable insights on the optimal thermal and cost operations of the system
The amino acid sequence of a cereal Bowman-Birk type trypsin inhibitor from seeds of Jobs' tears (Coix lachryma-jobi L.)
No full textAbstractThe major trypsin inhibitor from seeds of Jobs' tears (Coix lachryma-jobi) was purified by heat treatment, fractional precipitation with (NH4)2SO4, ion-exchange chromatography on DEAE-Sepharose, gel-filtration on Sephadex G-75 and preparative reverse-phase HPLC. The complete amino acid sequence was determined by analysis of peptides derived from the reduced and S-carboxymethylated protein by digestion with trypsin, chymotrypsin and the S. aureus V8 protease. The polypeptide contained 64 amino acids with a high content of cysteine. The sequence exhibited strong homology with a number of Bowman-Birk inhibitors from legume seeds and similar proteins recently isolated from wheat and rice
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