Aging differentially affects LTCC function in hippocampal CA1 and piriform cortex pyramidal neurons

Aging is associated with cognitive decline and memory loss in humans. In rats, aging-associated neuronal excitability changes and impairments in learning have been extensively studied in the hippocampus. Here, we investigated the roles of L-type calcium channels (LTCCs) in the rat piriform cortex (PC), in comparison with those of the hippocampus. We employed spatial and olfactory tasks that involve the hippocampus and PC. LTCC blocker nimodipine administration impaired spontaneous location recognition in adult rats (6-9 months). However, the same blocker rescued the spatial learning deficiency in aged rats (19-23 months). In an odor-associative learning task, infusions of nimodipine into either the PC or dorsal CA1 impaired the ability of adult rats to learn a positive odor association. Again, in contrast, nimodipine rescued odor associative learning in aged rats. Aged CA1 neurons had higher somatic expression of LTCC Cav1.2 subunits, exhibited larger afterhyperpolarization (AHP) and lower excitability compared with adult neurons. In contrast, PC neurons from aged rats showed higher excitability and no difference in AHP. Cav1.2 expression was similar in adult and aged PC somata, but relatively higher in PSD95- puncta in aged dendrites. Our data suggest unique features of aging-associated changes in LTCCs in the PC and hippocampus.

Conditional over-expression of heme-oxygenase 1 in myelomonocytic cells reduces hypertension and vascular inflammation

Background

Arterial hypertension is one of the most important modifiable risk factors for all-cause morbidity and mortality worldwide. Angiotensin II (Ang II) plays a pathogenic role in the development of hypertension, vascular dysfunction, inflammation and tissue damage. In the context of hypertension, heme-oxygenase 1 (HO-1) gene expression is upregulated as an antioxidant defense system in response to AngII through its action on heme catabolism, which generates carbon monoxide (CO), ferritin and biliverdin, which is reduced to bilirubin by biliverdin reductase A (BLVRA). Previous studies have shown the important role of HO-1 in the maturation and migration of immune cells. Myeloid HO-1 modulates macrophage polarization and protects against ischemia-reperfusion damage. However, the role of myeloid cell specific HO-1 in the detrimental effects of AngII induced vascular dysfunction has not yet been explored.

Objectives

To investigate the potential vascular protection of myeloid cell specific overexpression of HO-1 in AngII-induced arterial hypertension.

Methods

Hypertension was induced in 8–13 weeks old male mice with selective over-expression of HO-1 (HO-1indLysMcre) in myelomonocytic cells versus LysMCre/wt by AngII infusion (1mg/kg/d). Blood pressure was recorded by tail-cuff. Bilirubin levels were quantified in plasma by High Performance Liquid Chromatography (HPLC). The quantification of adherent and rolling leukocytes in carotid arteries was detected by intravital video microscopy (IVM). Endogenuos Thrombin potential (ETP) was measured in platelet rich plasma (PRP) and platelets poor plasma (PPP) by Calibrated Automated Thrombogram (CAT) assay. Endothelium-dependent vasodilation was assessed in isolated aortic rings by concentration-relaxation curves in response to acetylcholine (ACh).

Results

AngII-infused HO-1indLysMcre had decreased blood pressure values and improved endothelial function as compared to LysMcre controls. IVM revealed reduced leukocyte rolling and adhesion to the vascular endothelium in AngII infused HO-1indLysMcre mice compared to controls, paralleled by reduced expression of NOX-2 mediated oxidative stress and vascular inflammation in AngII-induced arterial hypertension by decreasing VCAM-1, CCR2 and MCP-1 expression. mRNA analysis revealed an increased expression of BLVRA in liver, spleen, heart and aortic tissues in response to AngII, which was higher in HO-1indLysMcre mice than in controls. By CAT assay we registered a decrease ETP in PPP and PRP in HO-1ind mice infused with AngII compatible with less abundance of inflammatory platelets, potentially regulated by BLVRA activity. This was supported by increased in bilirubin levels in response to AngII, which was higher in HO-1indLysMcre mice than in controls.

Conclusion

Myeloid cell specific overexpression of HO-1 confers anti-inflammatory protection to the vasculature in AngII induced hypertension. This effect is, at least in part, mediated by BLVRA.

Funding Acknowledgement

Type of funding sources: None.

Novelty-like activation of locus coeruleus protects against deleterious human pretangle tau effects while stress-inducing activation worsens its effects

The earliest abnormality associated with Alzheimer's disease (AD) is the presence of persistently phosphorylated pretangle tau in locus coeruleus (LC) neurons. LC neuron numbers and fiber density are positive predictors of cognition prior to death. Using an animal model of LC pretangle tau, we ask if LC activity patterns influence the sequelae of pretangle tau. We seeded LC neurons with a pretangle human tau gene. We provided daily novelty- or stress-associated optogenetic activation patterns to LC neurons for 6 weeks in mid-adulthood and, subsequently, probed cognitive and anatomical changes. Prior LC phasic stimulation prevented spatial and olfactory discrimination deficits and preserved LC axonal density. A stress-associated activation pattern increased indices of anxiety and depression, did not improve cognition, and worsened LC neuronal health. These results argue that variations in environmental experiences associated with differing LC activity patterns may account for individual susceptibility to development of AD in humans.

Locus Coeruleus Activation Patterns Differentially Modulate Odor Discrimination Learning and Odor Valence in Rats

The locus coeruleus (LC) produces phasic and tonic firing patterns that are theorized to have distinct functional consequences. However, how different firing modes affect learning and valence encoding of sensory information are unknown. Here, we show bilateral optogenetic activation of rat LC neurons using 10-Hz phasic trains of either 300 ms or 10 s accelerated acquisition of a similar odor discrimination. Similar odor discrimination learning was impaired by noradrenergic blockade in the piriform cortex (PC). However, 10-Hz phasic light-mediated learning facilitation was prevented by a dopaminergic antagonist in the PC, or by ventral tegmental area (VTA) silencing with lidocaine, suggesting a LC–VTA–PC dopamine circuitry involvement. Ten-hertz tonic stimulation did not alter odor discrimination acquisition, and was ineffective in activating VTA DA neurons. For valence encoding, tonic stimulation at 25 Hz induced conditioned odor aversion, whereas 10-Hz phasic stimulations produced an odor preference. Both conditionings were prevented by noradrenergic blockade in the basolateral amygdala (BLA). Cholera Toxin B retro-labeling showed larger engagement of nucleus accumbens-projecting neurons in the BLA with 10-Hz phasic activation, and larger engagement of central amygdala projecting cells with 25-Hz tonic light. These outcomes argue that the LC activation patterns differentially influence both target networks and behavior.

Nanomaterial–microbe cross-talk: physicochemical principles and (patho)biological consequences

NPs’ characteristics impact their spontaneous binding to microbes, which may affect the (patho)biological identity of both NP and microbes.

New locations of intravascular tissue factor

Tissue factor (TF) is the major initiator of blood coagulation, and a mediator of inflammation, angiogenesis, and carcinogenesis. According to recent evidence, preformed TF and inducible expression of the protein is observed in several blood components. TF is apparently constitutively expressed on circulating microparticles, and can be exposed within minutes on the cell membrane of activated eosinophils and platelets, and, potentially, on neutrophils. Expression in monocytes and neutrophils largely requires transcriptional activation of the TF gene. Eosinophils appear to harbour the highest concentration of preformed TF among all blood components under resting conditions. TF expression in eosinophil progenitor cells is substantially higher than in precursors of other granulocyte fractions. Eosinophil TF promotes transendothelial migration, which documents that presynthesized TF in blood supports functions apart from coagulation. It is still an open question how the intravascular TF is activated to trigger initiation of coagulation. TF activation in different blood components is likely to be differentially regulated according to the (patho)physiologic context.

Twenty-four hour Holter monitoring in finishing cattle housed outdoors

INTRODUCTION

Atrial premature complexes have been reported to be the most common arrhythmia in cattle and is suspected to be secondary to systemic disease, especially gastrointestinal disease. In order to properly identify pathologic arrhythmia in cattle, the normal rhythm and arrhythmia prevalence should be defined. The objective of this study was to determine the normal heart rate, rhythm, number of ventricular premature complexes (VPCs), and atrial premature complexes (APCs) in unrestrained Angus steers.

ANIMALS

Twenty-seven client owned steers with unremarkable physical examinations and serum biochemical analyses were used.

MATERIALS AND METHODS

Twenty-four hour Holter monitors, attached by a custom-made harness, were retrospectively evaluated. Three lead electrocardiographic registrations of good quality and normal sinus rhythm were obtained from all steers in the study.

RESULTS

The mean heart rate was 66.8 bpm ± 16.4 bpm. Ventricular premature complexes were rare (noted in 14.8% of steers), and APCs were common (noted in 85% of the steers). Simple second degree AV block was observed in 18.5% of the steers.

CONCLUSION

In summary, healthy steers have rare single VPCs, although it is possible for an individual animal to have apparent more frequent VPCs. Mean heart rate varies with a diurnal pattern similar to other species. Atrial premature complexes are the most prevalent abnormality observed in feedlot steers.

Cofactor-independent human antiphospholipid antibodies induce venous thrombosis in mice

Essentials Cofactor-independent antiphospholipid antibodies (CI-aPL) are generally considered non-pathogenic. We analyzed the effects of human monoclonal CI-aPL in a mouse model of venous thrombosis. As shown in vitro, CI-aPL induce a procoagulant state in vivo by activation of endosomal NADPH-oxidase. Contrary to common belief, CI-aPL induce venous thrombosis in vivo.

SUMMARY

Background There is general consensus that the antiphospholipid syndrome (APS) is caused by antiphospholipid antibodies (aPL) with antibodies against β2-glycoprotein-I being the most relevant. aPL that bind phospholipids in the absence of protein cofactors are generally considered pathogenetically irrelevant. We showed that cofactor-independent human monoclonal aPL isolated from APS patients induce proinflammatory and procoagulant cellular responses by activating endosomal NADPH-oxidase 2 (NOX2). Similar aPL were detected in all IgG fractions from APS patients analyzed. Objectives We aimed to clarify if cofactor-independent aPL can be thrombogenic in vivo and, if so, whether these effects are mediated via activation of NOX2. Methods Two cofactor-independent human monoclonal aPL, HL5B and RR7F, were tested in a mouse model of venous thrombosis. Genetically modified mice and in vitro assays were used to delineate the mechanisms underlying thrombus induction. Results HL5B and RR7F dramatically accelerate thrombus formation in this mouse model. Thrombus formation depends on tissue factor activation. It cannot be induced in NOX2-deficient mice. Bone marrow chimeras of C57BL/6J mice reconstituted with NOX2-deficient bone marrow showed that leukocyte activation plays a major role in thrombus formation. Neither TLR4 signaling nor platelet activation by our aPL is required for venous thrombus formation. Conclusions Cofactor-independent aPL can induce thrombosis in vivo. This effect is mainly mediated by leukocyte activation, which depends on the previously described signal transduction via endosomal NOX2. Because most APS patients have been shown to harbor aPL with similar activity, our data are of general relevance for the APS.

An open-label, randomized phase II study of adecatumumab, a fully human anti-EpCAM antibody, as monotherapy in patients with metastatic breast cancer

BACKGROUND

High-level expression of epithelial cell adhesion molecule (EpCAM) is associated with unfavorable prognosis in breast cancer. This study was designed to investigate two doses of the fully human IgG1 anti-EpCAM antibody adecatumumab (MT201) in patients with metastatic breast cancer (MBC).

METHODS

A total of 109 patients were stratified into high- and low-level EpCAM expression by immunohistochemical staining of primary tumors and subsequently randomly assigned to receive monotherapy with either high- (6 mg/kg every two weeks (q2w)) or low-dose adecatumumab (2 mg/kg/ q2w) until disease progression.

RESULTS

No complete or partial tumor responses could be confirmed by central RECIST assessment. The probability for tumor progression was significantly lower in patients receiving high-dose adecatumumab and expressing high levels of EpCAM (hazard ratio 0.43; P = 0.0057 versus low dose and low EpCAM). Three of 18 patients with highest EpCAM expression treated with adecatumumab developed new metastases up to week 6, compared with 14 of 29 patients with low EpCAM. Most frequent treatment-related adverse events (high dose/low dose) were chills (59%/20%), nausea (55%/18%), fatigue (39%/23%) and diarrhea (43%/7%).

CONCLUSIONS

Single-agent adecatumumab shows dose- and target-dependent clinical activity in EpCAM-positive MBC, albeit no objective tumor regression. Further investigation of adecatumumab in patients with EpCAM-overexpressing tumors and lower tumor burden is warranted.

Safety and antitumor activity of 3-weekly anti-EpCAM antibody adecatumumab (MT201) in combination with docetaxel for patients with metastatic breast cancer: Results of a multicenter phase Ib trial

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Background: The fully human IgG1 antibody adecatumumab (MT201) binds to the epithelial cell adhesion molecule (EpCAM), which is expressed in over 90% of breast cancers and has been associated with poor prognosis. Data from a previous phase II study in metastatic breast cancer (MBC) indicated that single agent MT201 could prolong progression-free survival in a subset of patients with high EpCAM expression. This study tested safety and tolerability of MT201 treatment in combination with standard docetaxel. Methods: Relapsed or primary refractory, EpCAM-positive MBC patients were treated with docetaxel (100 mg/m2 q21d) in combination with MT201 (dose levels 180 mg/m2, and 550 mg/m2 q21d). A loading dose of 100 mg/m2 and 300 mg/m2, respectively, was administered on day 1 and 7. Patients were grouped into high- and low-level EpCAM expression. Primary objectives were safety and tolerability; anti-tumor activity according to RECIST was a secondary objective. Results: A total of 22 patients with a median of 3 prior chemotherapy lines were enrolled. Most frequent grade 3/4 adverse events (AE) in all patients were leucopenia (90%), neutropenia (77%), lymphopenia (68%), and diarrhea (23%). No evidence for aggravation of grade 3/4 toxicities typically associated with docetaxel was found. The dose level 550 mg/m2 q21d has been determined as MTD in combination with 100 mg/m2 q21d docetaxel. The overall response rate (CR/PR; RECIST) and clinical benefit rate (CR/PR and SD>24wks) in all evaluable patients was 24% and 41%, respectively. Patients with high EpCAM expression showed a response rate of 43%, whereas patients with low EpCAM expression had a response rate of 10%. Median time-to-progression (TTP) in all evaluable patients was 165 days. Conclusions: Combining MT201 with docetaxel for the treatment of MBC appears to be safe and feasible. The DLT of this combination were short and manageable episodes of grade 3 diarrhea. The response rate and TTP observed in this heavily pre-treated population is encouraging and warrant further development of MT201/chemotherapy combinations in patients with tumors of high EpCAM target level.

[Table: see text]

National Hand Hygiene Campaigns in Europe, 2000-2009

Hand hygiene represents the single most effective way to prevent healthcare-associated infections. The World Health Organization, as part of its First Global Patient Safety Challenge, recommends implementation of multi-faceted strategies to increase compliance with hand hygiene. A questionnaire was sent by the European Centre for Disease Prevention and Control to 30 European countries, regarding the availability and organisation of their national hand hygiene campaigns. All countries responded. Thirteen countries had organised at least one national campaign during the period 2000-2009 and three countries were in the process of organising a national campaign. Although the remaining countries did not have a national campaign, several reported regional and local hand hygiene activities or educational resources on national websites.

National hand hygiene campaigns in Europe, 2000-2009

Hand hygiene represents the single most effective way to prevent healthcare-associated infections. The World Health Organization, as part of its First Global Patient Safety Challenge, recommends implementation of multi-faceted strategies to increase compliance with hand hygiene. A questionnaire was sent by the European Centre for Disease Prevention and Control to 30 European countries, regarding the availability and organisation of their national hand hygiene campaigns. All countries responded. Thirteen countries had organised at least one national campaign during the period 2000-2009 and three countries were in the process of organising a national campaign. Although the remaining countries did not have a national campaign, several reported regional and local hand hygiene activities or educational resources on national websites.

Focusing and directing of surface plasmon polaritons by curved chains of nanoparticles

Excitation, focusing and directing of surface plasmon polaritons (SPPs) with curved chains of nanoparticles located on a metal surface is investigated both experimentally and theoretically. We demonstrate that, by using a relatively narrow laser beam (at normal incidence) interacting only with a portion of a curved chain of nanoparticles, one can excite an SPP beam whose divergence and propagation direction are dictated by the incident light spot size and its position along the chain. It is also found that the SPP focusing regime is strongly influenced by the chain inter-particle distance. Extensive numerical simulations of the configuration investigated experimentally are carried out for a wide set of system parameters by making use of the Green's tensor formalism and dipole approximation. Comparison of numerical results with experimental data shows good agreement with respect to the observed features in SPP focusing and directing, providing the guidelines for a proper choice of the system parameters.

Final results from an open-label, randomised, phase II study of adecatumumab (MT201), a fully human anti-EpCAM antibody, in patients with metastatic breast cancer

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Background: High-level expression of the epithelial cell adhesion molecule (EpCAM) has been associated with unfavourable prognosis in various cancers. Adecatumumab was developed as a low-affinity IgG1 antibody targeting EpCAM-positive cancer cells. Methods: EpCAM-positive metastatic breast cancer patients without CNS metastases, with no indication for trastuzumab were eligible; an initial restriction to a maximum of one previous chemotherapy for metastatic disease was subsequently removed. 109 EpCAM- positive patients were enrolled. Patients were stratified into high- and low-level EpCAM expression (n = 74 and 35, respectively) according to immuno-histochemistry testing, and subsequently randomised to receive either high-dose (6 mg/kg/q2w) or low-dose (2 mg/kg/q2w) adecatumumab (n = 54 and 55, respectively). Primary endpoint was clinical benefit rate (CBR = objective response + stable disease) at week 24 with secondary parameters exploring time to progression (TTP) and safety. Results: The primary endpoint (CBR at week 24: >25%) was not met in any of the 4 groups according to central radiological review. Exploratory analyses of the Kaplan-Meier curves, however, showed a lower probability for tumor progression in patients receiving high dose adecatumumab (HR: 0.67 [0.47–0.94]; p=0.047). A similar trend was also observed in patients with high-level EpCAM expression (HR: 0.71 [0.49–1.03]; p=0.116). Further (retrospective) analysis using more stringent criteria for the definition of high-level EpCAM expression indicated an inverse correlation of staining intensity and frequency with probability of progression. An increased incidence of CTC grade 1 and 2 AE was found in the high-dose group with main side effects being gastrointestinal and constitutional symptoms. Conclusions: The observation of dose- and target-dependent activity of adecatumumab warrants further investigation. Definition of the optimum dose and regimen as well as exploration of the predictive value of EpCAM testing will be key in future development.

No significant financial relationships to disclose.

New locations of intravascular tissue factor: indications

Tissue factor (TF) is the major initiator of blood coagulation, and a mediator of inflammation, angiogenesis, and carcinogenesis. According to recent evidence, preformed TF and inducible expression of the protein is observed in several blood components. TF is apparently constitutively expressed on circulating microparticles, and can be exposed within minutes on the cell membrane of activated eosinophils and platelets, and, potentially, on neutrophils. Expression in monocytes and neutrophils largely requires transcriptional activation of the TF gene. Eosinophils appear to harbour the highest concentration of preformed TF among all blood components under resting conditions. TF expression in eosinophil progenitor cells is substantially higher than in precursors of other granulocyte fractions. Eosinophil TF promotes transendothelial migration, which documents that presynthesized TF in blood supports functions apart from coagulation. It is still an open question how the intravascular TF is activated to trigger initiation of coagulation. TF activation in different blood components is likely to be differentially regulated according to the (patho)physiologic context.

Changes in function and morphology of normal human skin: evaluation using optical coherence tomography

BACKGROUND

Optical coherence tomography (OCT) is a noninvasive morphological method for investigating human skin. It allows high-resolution in vivo imaging of inflammatory skin diseases and tumours. Because it is a newly developed method, systematic studies on standardization and on evaluation of factors influencing the representation of the skin have not yet been performed.

OBJECTIVES

In this study, normal human skin was treated with various external stimuli which induce changes of function and morphology. Changes in stratum corneum thickness as well as changes induced by pigmentation, oedema and erythema were investigated using OCT.

METHODS

Healthy skin of human volunteers was treated with tape stripping, ultraviolet A irradiation, water, histamine, nicotinic acid and various ointments.

RESULTS

In the tape stripping experiment, the thickness of the horny layer was quantified and monitored. Pigmentation increased the light attenuation of the tissue, whereas hydration and erythema led to a slight decrease of scattering. Topical treatment of the skin gave a nonspecific increase of penetration depth of the light due to the lower reflectivity of the surface.

CONCLUSIONS

There are various physiological conditions which influence optical properties of the skin. These parameters should be considered when performing standardized OCT studies.

Minimal flow sevoflurane and isoflurane anaesthesia and impact on renal function

BACKGROUND AND AIM

Compound A generation and accumulation in sevoflurane anaesthesia is dependent on fresh gas flow. We investigated the extent of generation of compound A.

METHODS

After Institutional Review Board approval and informed consent, patients with normal renal function were randomized to receive either sevoflurane (n = 33) or isoflurane (n = 43) minimal flow anaesthesia (0.5 L min-1) for at least 2 h under standardized conditions. Compound A concentrations were quantified and blood and urine samples were taken to assess renal involvement. Both groups were comparable.

RESULTS

No significant differences concerning blood chemistry and urine measurements were found. The maximum mean compound A concentration was observed 90 min after flow reduction being 40 +/- 9 p.p.m. at a corresponding mean sevoflurane concentration of 2.1 +/- 0.5 vol%. Mean inspiratory compound A exposure was 102 +/- 33 p.p.m h-1.

CONCLUSION

Compound A concentrations using 0.5 L min-1 fresh gas flow and a heated absorber were higher than previously published values using an inflow of 1 L min-1. Compound A exposure was similar to other clinical studies which did not show changes in renal and hepatic function.

Normalization of elevated CD4-/CD8- (double-negative) T cells after thymectomy parallels clinical remission in myasthenia gravis associated with thymic hyperplasia but not thymoma

T-cell-dependent B-cell help is likely to be of major importance in the pathogenesis of myasthenia gravis, but mechanisms provoking a pathological anti-acetylcholine receptor (AChR) response are poorly understood. We report on the dysregulation of recently identified CD4-/CD8- (double-negative) T cells (DN T cells), which have been shown to participate in immunoregulation and antibody augmentation. Compared with healthy controls, significantly increased frequencies of DN T cells were found in the blood of myasthenia gravis patients with lymphofollicular hyperplasia. After thymectomy, however, normalization in the number of these cells was seen in parallel with clinical improvement and reduction in anti-AChR antibody titers. The effect of thymectomy was observed irrespective of adjuvant treatment and held true for up to 4 years of follow-up. In marked contrast, frequencies similar to control values were found in myasthenia gravis patients with thymoma, with thymectomy having no further reducing effect. These data indicate that CD4-/CD8- T cells not only participate in the pathogenesis of myasthenia gravis but also correlate with disease activity and histological findings.

Self-induced parametric amplification of high-order harmonics

A theoretical analysis of self-induced parametric amplification of high-order harmonics is given. This mechanism permits the elimination of limitations on the harmonic-generation efficiency that are imposed by absorption.

Patients with dilated cardiomyopathy and less than 20% ejection fraction increase exercise capacity and have less severe arrhythmia after controlled exercise training

The results of this pilot study suggest that patients with a diminished ejection fraction as low as 16% can safely perform an exercise program. A significant improvement in peak VO2 and maximal work rate was achieved. Moreover, this study suggests that exercise training might diminish the severity of asymptomatic ventricular arrhythmia; however a larger controlled study is needed to confirm these findings.

Elevated frequencies of natural killer T lymphocytes in myasthenia gravis

T lymphocytes are considered to exert a regulatory function in the development of antiacetylcholine receptor antibodies, but no clear T-cell alterations in patients with myasthenia gravis (MG) have yet been found. The authors report a significant increase of recently identified natural killer T lymphocytes expressing T-cell receptor Valpha24. A possible role in disease initiation or maintenance is suggested by the observed strong synthesis of interferon-gamma as well as of interleukin 4.

Skewed TCRV beta repertoire in human thymus persists after thymic emigration: influence of genomic imposition, thymic maturation and environmental challenge on human TCRV beta usage in vivo

In order to investigate the mechanisms involved in originating a diverse TCR repertoire in human peripheral blood we analyzed TCRV beta surface expression in different T cell subsets of unrelated individuals. The relative frequencies of 11 distinct V beta chains were determined for immature double positive (DP) as well as for mature CD4 single positive (4SP) and CD8 single positive (8SP) thymocytes, respectively. By comparing these data with expression in peripheral blood T lymphocytes of the same donors we were able to show that usage of TCRV beta in peripheral T cells is significantly (p < 0.001) depending on the pattern in mature SP thymocytes whereas the frequency of TCRV beta families in immature DP thymocytes has no impact (p > 0.2). No association with distinct HLA-haplotypes was observed. Preferential usage of V beta-families in either CD4- or CD8-positive peripheral T cells also correlates with the status in mature thymic precursors (p < 0.001). Altogether, this first combined study of TCR frequencies within different stages of human T cell ontogeny indicates that TCRV beta repertoire is determined mainly through selectional processes within the thymus. Since neither genomically imposed expression nor modulating events in the periphery seem to have strong influence on the relative expression of TCRV beta chains these findings have to be considered in future studies of human diseases.

Different activation energies in glucose uptake in Saccharomyces cerevisiae DFY1 suggest two transport systems

The analysis of initial glucose uptake in Saccharomyces cerevisiae at 25 degrees, 20 degrees, 15 degrees and 10 degrees C by computer-assisted nonlinear regression analysis predicts two transport systems. The first demonstrates Michaelis-Menten kinetics and the second shows first order behaviour. The activation energies of these two systems were calculated by the Arrhenius equation at four different growth phases, namely early exponential (EE), middle exponential (ME2), late exponential (LE) and early stationary (ES) with 2% glucose in the batch medium. The activation energies calculated from the V(m) values in EE, ME, LE and ES growth phases were 15.8 +/- 1.7, 13.5 +/- 1.0, 15.1 +/- 0.8 and 13.5 +/- 0.7 kcal/mol. These values are in agreement with activation energies calculated for the first mechanism, facilitated diffusion, which is the mechanism deduced from countertransport experiments. The activation energies derived for the second transport system from the first order rate constants in cells grown to EE, ME2, LE and ES were 8.0 +/- 2.1, 8.1 +/- 1.3, 9.6 +/- 3.0 and 7.5 +/- 2.6 kcal/mol. These values are still significantly higher than for free diffusion of glucose in water and lower as predicted for passage of glucose through the lipid phase. Therefore, we assume in addition to carrier-mediated facilitated diffusion the entrance of glucose into the cell through a pore.

Effects of diadenosine polyphosphates on renal function and blood pressure in anesthetized Wistar rats

In this study, the effects of diadenosine polyphosphates on kidney function were examined. Intravenous application of diadenosine hexaphosphate (AP6A) led to a significant threefold increase in both urine flow (from 2.45 +/- 0.2 to 13.8 +/- 0.74 microL/min per 100 g body wt (P < 0.05)) and Na+ excretion (from 0.41 +/- 0.12 to 1.52 +/- 0.28 mumol/min per 100 g body wt at a dose of 1.0 mg/kg body wt). In contrast, diadenosine triphosphate dose-dependently reduced urine flow (from 3.74 +/- 0.3 to 2.57 +/- 0.1 microL/min per 100 g body wt (P < 0.05)) and Na+ excretion (from 0.45 +/- 0.1 to 0.13 +/- 0.1 mumol/min per 100 g body wt at a dose of 1.0 mg/kg body wt). ATP and the P2y purinoceptor agonist gamma-S-ATP did not significantly modulate urine flow and Na+ excretion. alpha, beta-methylene-ATP, a P2x purinoceptor agonist, significantly increased urine flow from 1.74 +/- 0.5 to 4.07 +/- 1.51 microL/min per 100 g body wt, whereas Na+ excretion was unaffected. The effects were independent of alterations in GFR. Pretreatment with indomethacin (2.0 mg/kg body wt iv) completely abolished the effects of AP6A on urine flow and Na+ excretion. Similarly, pretreatment with the endothelin antagonist bosentan abolished the effects of AP6A on both urine flow and Na+ excretion, whereas suramin had no effects on the AP6A-induced increase in urine flow. In conclusion, diadenosine polyphosphates exert specific actions on urine flow and Na+ excretion that are different from the effects of ATP. AP6A may partially influence renal function by stimulating prostaglandin and endothelin release.