An upper limit on the stochastic gravitational-wave background of cosmological origin.

A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin. It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standard astrophysical observations. Direct measurements of the amplitude of this background are therefore of fundamental importance for understanding the evolution of the Universe when it was younger than one minute. Here we report limits on the amplitude of the stochastic gravitational-wave background using the data from a two-year science run of the Laser Interferometer Gravitational-wave Observatory (LIGO). Our result constrains the energy density of the stochastic gravitational-wave background normalized by the critical energy density of the Universe, in the frequency band around 100 Hz, to be <6.9 x 10(-6) at 95% confidence. The data rule out models of early Universe evolution with relatively large equation-of-state parameter, as well as cosmic (super)string models with relatively small string tension that are favoured in some string theory models. This search for the stochastic background improves on the indirect limits from Big Bang nucleosynthesis and cosmic microwave background at 100 Hz.

Mitochondrial adaptations evoked with exercise are associated with a reduction in age-induced testicular atrophy in Fischer-344 rats.

Mitochondrial dysfunction in various tissues has been associated with numerous conditions including aging. In testes, aging induces atrophy and a decline in male reproductive function but the involvement of mitochondria is not clear. The purpose of this study was to examine whether the mitochondrial profile differed with (1) aging, and (2) 10-weeks of treadmill exercise training, in the testes of young (6 month) and old (24 month) Fischer-344 (F344) animals. Old animals exhibited significant atrophy (30 % decline; P < 0.05) in testes compared to young animals. However, relative mitochondrial content was not reduced with age and this was consistent with the lack of change in the mitochondrial biogenesis regulator protein, peroxisome proliferator-activated receptor gamma coactivator 1-alpha and its downstream targets nuclear respiratory factor-1 and mitochondrial transcription factor A. No effect was observed in the pro- or anti-apoptotic proteins, Bax and Bcl-2, respectively, but age increased apoptosis inducing factor levels. Endurance training induced beneficial mitochondrial adaptations that were more prominent in old animals including greater increases in relative mtDNA content, biogenesis/remodeling (mitofusin 2), antioxidant capacity (mitochondrial superoxide dismutase) and lower levels of phosphorylated histone H2AX, an early marker of DNA damage (P < 0.05). Importantly, these exercise-induced changes were associated with an attenuation of testes atrophy in older sedentary animals (P < 0.05). Our results indicate that aging-induced atrophy in testes may not be associated with changes in relative mitochondrial content and key regulatory proteins and that exercise started in late-life elicits beneficial changes in mitochondria that may protect against age-induced testicular atrophy.

Directional limits on persistent gravitational waves using LIGO S5 science data.

The gravitational-wave (GW) sky may include nearby pointlike sources as well as stochastic backgrounds. We perform two directional searches for persistent GWs using data from the LIGO S5 science run: one optimized for pointlike sources and one for arbitrary extended sources. Finding no evidence to support the detection of GWs, we present 90% confidence level (C.L.) upper-limit maps of GW strain power with typical values between 2-20×10(-50) strain(2) Hz(-1) and 5-35×10(-49) strain(2) Hz(-1) sr(-1) for pointlike and extended sources, respectively. The latter result is the first of its kind. We also set 90% C.L. limits on the narrow-band root-mean-square GW strain from interesting targets including Sco X-1, SN 1987A and the Galactic center as low as ≈7×10(-25) in the most sensitive frequency range near 160 Hz.

DEVELOPMENT OF A NEW SECONDARY STANDARD FOR H*(10).

A secondary standard for ambient dose equivalent, H*(10), is necessary for the dissemination of the unit Sievert (Sv), but there is no such standard commercially available currently. Furthermore, the measurement of H*(10) instead of calculating H*(10) from air kerma and conversion coefficients is needed for unknown radiation fields. We developed a prototype of a new secondary standard for H*(10) based on a spherical 1 l ionization chamber for air kerma. This chamber was modified with copper wires at the inner surface to adjust the response of the chamber according to H*(10). Additionally, a Makrolon shell and an aluminium coating were added to optimize the response at energies below 50 keV. The prototype fulfils the requirements given in ISO 4037-2 in the energy range from 12 keV to 7 MeV. In combination with an electrometer, it can be used as area dosemeter, suitable for pulsed fields and for low energy radiation.

Novel spectrometers for environmental dose rate monitoring.

A new generation of dosemeters, based on the scintillators LaBr3, CeBr3 and SrI2, read out with conventional photomultipliers, to be used in the field of environmental gamma-radiation monitoring, was investigated. The main features of these new instruments and especially their outdoor performance, studied by long-term investigations under real weather conditions, are presented. The systems were tested at the reference sites for environmental radiation of the Physikalisch-Technische Bundesanstalt. The measurements are compared with that of well characterized classical dose rate reference instruments to demonstrate the suitability of new spectrometers for environmental dose rate monitoring even in adverse weather conditions. Their potential to replace the (mainly Geiger Müller based) dose rate meters operated in about 5000 European early waning network stations as well as in environmental radiation monitoring in general is shown.

Downhill treadmill running trains the rat spinotrapezius muscle.

There are currently no models of exercise that recruit and train muscles, such as the rat spinotrapezius, that are suitable for transmission intravital microscopic investigation of the microcirculation. Recent experimental evidence supports the concept that running downhill on a motorized treadmill recruits the spinotrapezius muscle of the rat. Based on these results, we tested the hypothesis that 6 wk of downhill running (-14 degrees grade) for 1 h/day, 5 days/wk, at a speed of up to 35 m/min, would 1) increase whole body peak oxygen uptake (Vo(2 peak)), 2) increase spinotrapezius citrate synthase activity, and 3) reduce the fatigability of the spinotrapezius during electrically induced 1-Hz submaximal tetanic contractions. Trained rats (n = 6) elicited a 24% higher Vo(2 peak) (in ml.min(-1).kg(-1): sedentary 58.5 +/- 2.0, trained 72.7 +/- 2.0; P < 0.001) and a 41% greater spinotrapezius citrate synthase activity (in mumol.min(-1).g(-1): sedentary 14.1 +/- 0.7, trained 19.9 +/- 0.9; P < 0.001) compared with sedentary controls (n = 6). In addition, at the end of 15 min of electrical stimulation, trained rats sustained a greater percentage of the initial tension than their sedentary counterparts (control 34.3 +/- 3.1%, trained 59.0 +/- 7.2%; P < 0.05). These results demonstrate that downhill running is successful in promoting training adaptations in the spinotrapezius muscle, including increased oxidative capacity and resistance to fatigue. Since the spinotrapezius muscle is commonly used in studies using intravital microscopy to examine microcirculatory function at rest and during contractions, our results suggest that downhill running is an effective training paradigm that can be used to investigate the mechanisms for improved microcirculatory function following exercise training in health and disease.

CAN HALF VALUE LAYER MEASUREMENTS BE USED TOGETHER WITH THE EFFECTIVE ENERGY TO OBTAIN CONVERSION COEFFICIENTS FOR X-RAY SPECTRA?

Conversion coefficients are a substantial vehicle in practical radiation protection to determine the dose (rate) of a given radiation field. According to ICRU report 57, their values shall be obtained by means of spectrometry. This is, however, a time-consuming complicated procedure that cannot be performed by all dosimetry laboratories. Therefore, it is desired to find acceptable alternative methods to replace spectrometry. One possibility is to set up the X-ray facility in accordance with international standard ISO 4037-1:1997 and use the tabulated values from that standard. However, this needs to be considered during the construction phase of the X-ray facility. In this work, the combined usage of half-value layer measurements and the effective energy (both with respect to air kerma) to determine the conversion coefficients is investigated and compared with the values obtained by spectrometry. The investigations utilise all combinations of the H-, W-, N- and L-series, reference distances of 1 and 2.5 m and aluminium and copper as attenuation materials. We find that for most of the radiation qualities, the investigated method results in conversion coefficients that show an unacceptable deviation from the conventionally true values. However, the values of conversion coefficients of selected N- and L-qualities could be reproduced with high accuracy (within ±1 %).

Effect of X-ray High-voltage Variations on the Conversion Coefficients.

Conversion coefficients (CCs) are an essential vehicle in radiation protection for the determination of the dose (rate) of a given radiation field. According to the current draft of the revision of international standard ISO 4037, an X-ray field is a reference field if the CCs of the field match the tabulated ISO values within 2%. Deviations of the high-voltage (HV) tube-potential from its nominal value influence the resulting spectra and change the corresponding CCs. This work investigates the maximum allowable deviation of the HV from its nominal value such that the requirements of ISO 4037 remain fulfilled. This is achieved using both synthetic spectra created by a software simulation program and spectra measured at one of the X-ray facilities of the Physikalisch-Technische Bundesanstalt. The results are summarised in form of a new proposal for upper limit values which are suggested to be used in the next version of ISO 4037.

Implications of X-ray tube parameter deviations in X-ray reference fields.

For the purpose of radiation protection, ICRU Report 57/ICRP Publication 74 provides a list of monoenergetic conversion coefficients to be used with, among others, photon reference fields generated with X-ray tubes. A comprehensive definition of these photon reference fields can be found in international standard ISO 4037; however, it lacks thorough indication of the allowed deviations of essential parameters that influence these X-ray reference fields. These parameters are the high-voltage tube potential, the thickness of the beryllium window and the purity and thickness of the filter materials used to create different radiation qualities. Small variations of these parameters can lead to significant changes in the created X-ray spectra and, hence, the spectra-dependent conversion coefficients for phantom-related radiation-protection quantities. This can lead to situations in which the conversion coefficients listed in ISO 4037 cannot be used, resulting in time-consuming spectrometry measurements. In this work, the impact on the resulting conversion coefficients is investigated using a simplified mathematical approximation model. The findings are validated with an independent X-ray spectra calculation programme. As a result, well-founded upper limit values on the allowed deviations of the essential X-ray tube parameters are proposed to be used in a future revision of ISO 4037.

DNA polymerase alpha-DNA primase from human lymphoblasts.

The DNA polymerase alpha-DNA primase complex from the human lymphoblast line HSC93 has been enriched to near homogeneity by using an immunoaffinity purification protocol which was developed earlier for the purification of the calf thymus enzyme (Nasheuer, H.-P. and Grosse, F. (1987) Biochemistry 26, 8458-8466). Immunoaffinity purified polymerase-primase from human cells consisted of four subunits displaying molecular weights of 195,000 and 180,000 for the DNA synthesizing alpha-subunit, of 68,000 for the beta-subunit, and of 55,000 and 48,000 for the primase-carrying gamma- and delta-subunit, respectively. The isoelectric pH values for the individual subunits were estimated from non-equilibrium pH gradients to be between 5.9 and 5.7 for the alpha-subunit, at 5.5 for the beta-subunit, and at 7.5 and 8.0 for the gamma- and delta-subunit, respectively. The purified polymerase-primase converted single-stranded phi X174 DNA into the double-stranded form in a primase-initiated reaction. During this process, 3-10 RNA primers were formed. RNA primers were about 11 nucleotides long. Elongation of existing RNA primers by the human polymerase-primase was semi-processive; following primer binding the DNA polymerase continuously incorporated 20 to 50 nucleotides, then it dissociated from the template DNA.

Opposite effects of insulin and catecholamines on LDL-receptor activity in human mononuclear leukocytes.

The mechanisms by which insulin and catecholamines affect low-density lipoprotein (LDL)-receptor activity were studied in freshly isolated human mononuclear leukocytes. Incubation of cells for up to 24 h in a lipid-free medium resulted in an increase in the specific binding, accumulation, and degradation of 125I-labeled LDL. Insulin stimulated the ability of the cells to bind, accumulate, and degrade the lipoprotein with high affinity, which may be caused by an increase in the LDL-receptor number without altering binding affinity. (-)-Epinephrine inhibited the specific binding, accumulation, and degradation of 125I-LDL. This effect appears to be mediated by a decrease in the number of LDL receptors and not by a change in the binding affinity. (-)-Norepinephrine, the unspecific beta-adrenergic agonist (-)-isoproterenol, and the beta 2-specific agonist terbutaline mimicked the effect of epinephrine on LDL-receptor activity. Catecholamines and beta-adrenergic agonists yielded sigmoidal log-concentration effect curves. The action of epinephrine was attenuated by the beta-antagonist (dl)-propranolol. These results demonstrate that insulin stimulates and catecholamines suppress the specific binding, accumulation, and degradation of 125I-LDL in human mononuclear leukocytes. The catecholamine action appears to be mediated by beta 2-adrenergic receptors. A suppression of LDL-receptor activity resulting from deficiency of insulin and elevated plasma catecholamine concentrations in uncontrolled insulin-dependent diabetic patients may contribute to the increased levels of LDL cholesterol observed in these patients.

Dynamics of microvascular oxygen partial pressure in contracting skeletal muscle of rats with chronic heart failure.

OBJECTIVE: This investigation tested the hypothesis that the dynamics of muscle microvascular O(2) pressure (PO(2)m, which reflects the ratio of O(2) utilization [V*O(2)] to O(2) delivery [Q*O(2)]) following the onset of contractions would be altered in chronic heart failure (CHF). METHODS: Female Sprague-Dawley rats were subjected to a myocardial infarction (MI) or a sham operation (Sham). Six to 10 weeks post Sham (n=6) or MI (n=17), phosphorescence quenching techniques were utilized to determine PO(2)m dynamics at the onset of spinotrapezius muscle contractions (1 Hz). RESULTS: MI rats were separated into groups with Moderate (n=10) and Severe (n=7) CHF based upon the degree of left ventricular (LV) dysfunction as indicated by structural abnormalities (increased right ventricle weight and lung weight normalized to body weight). LV end-diastolic pressure was elevated significantly in both CHF groups compared with Sham (Sham, 3+/-1; Moderate CHF, 9+/-2; Severe CHF, 27+/-4 mmHg, P<0.05). The PO(2)m response was modeled using time delay and exponential components to fit the PO(2)m response to the steady-state. Compared with Shams, the time constant (tau) of the primary PO(2)m response was significantly speeded in Moderate CHF (tau, Sham, 19.0+/-1.5; Moderate CHF, 13.2+/-1.9 s, P<0.05) and slowed in Severe CHF (tau, 28.2+/-3.4 s, P<0.05). Within the Severe CHF group, tau increased linearly with the product of right ventricular and lung weight (r=0.83, P<0.05). CONCLUSIONS: These results suggest that CHF alters the dynamic matching of muscle V*O(2)-to-Q*O(2) across the transition from rest to contractions and that the nature of that perturbation is dependent upon the severity of cardiac dysfunction.

Effects of chronic heart failure on microvascular oxygen exchange dynamics in muscles of contrasting fiber type.

UNLABELLED: In rat spinotrapezius muscle, chronic heart failure (CHF) speeds microvascular O2 pressure (pO2; index of O2 delivery-to-O2 uptake) dynamics across the rest-contractions transition [Cardiovasc. Res. 56 (2002) 479]. Due to the mosaic nature of this muscle, the effect of CHF on microvascular pO2 dynamics in different fiber types remains unclear. OBJECTIVE: Based upon derangements of endothelial function and blood flow responses, we hypothesized that CHF would speed microvascular pO2 dynamics (reduced O2 delivery-to-O2 uptake ratio) in type I muscle (soleus, approximately 84% type I), but not in type II muscle (peroneal, approximately 86% type II [J. Appl. Physiol. 80 (1996) 261]). METHODS: Using phosphorescence quenching, microvascular pO2 was measured at rest and across the rest-contractions transition (1 Hz) in soleus and peroneal of non-infarcted control (control; n=7), and Sprague-Dawley rats with moderate (moderate; elevated left ventricular end-diastolic pressure (LVEDP) 10 +/- 2 mm Hg; n=10) and severe (severe; LVEDP 28 +/- 4 mm Hg; n=5) CHF. RESULTS: The microvascular pO2 mean response time (time delay+time constant) was progressively speeded with increasing severity of CHF in soleus (control, 38.7 +/- 2.0; moderate, 29.1 +/- 1.5; severe, 22.5 +/- 3.9 s; P< or =0.05), but not in peroneal (control=moderate=severe). CONCLUSION: As type I fibers are recruited predominately for moderate intensity exercise, the more rapid lowering of soleus microvascular pO2 in CHF would reduce the blood-muscle O2 driving gradient, exacerbate phosphocreatine and glycogen breakdown, and provide a mechanism for slowed O2 uptake kinetics and premature fatigue in CHF.

Plant extracts from stinging nettle (Urtica dioica), an antirheumatic remedy, inhibit the proinflammatory transcription factor NF-kappaB.

Activation of transcription factor NF-kappaB is elevated in several chronic inflammatory diseases and is responsible for the enhanced expression of many proinflammatory gene products. Extracts from leaves of stinging nettle (Urtica dioica) are used as antiinflammatory remedies in rheumatoid arthritis. Standardized preparations of these extracts (IDS23) suppress cytokine production, but their mode of action remains unclear. Here we demonstrate that treatment of different cells with IDS23 potently inhibits NF-kappaB activation. An inhibitory effect was observed in response to several stimuli, suggesting that IDS23 suppressed a common NF-kappaB pathway. Inhibition of NF-kappaB activation by IDS23 was not mediated by a direct modification of DNA binding, but rather by preventing degradation of its inhibitory subunit IkappaB-alpha. Our results suggests that part of the antiinflammatory effect of Urtica extract may be ascribed to its inhibitory effect on NF-kappaB activation.

Effects of the antirheumatic remedy hox alpha--a new stinging nettle leaf extract--on matrix metalloproteinases in human chondrocytes in vitro.

Inflammatory joint diseases are characterized by enhanced extracellular matrix degradation which is predominantly mediated by cytokine-stimulated upregulation of matrix metalloproteinase (MMP) expression. Besides tumour necrosis factor-alpha (TNF-alpha), Interleukin-1beta (IL-1beta) produced by articular chondrocytes and synovial macrophages, is the most important cytokine stimulating MMP expression under inflammatory conditions. Blockade of these two cytokines and their downstream effectors are suitable molecular targets of antirheumatic therapy. Hox alpha is a novel stinging nettle (Urtica dioica/Urtica urens) leaf extract used for treatment of rheumatic diseases. The aim of the present study was to clarify the effects of Hox alpha and the monosubstance 13-HOTrE (13-Hydroxyoctadecatrienic acid) on the expression of matrix metalloproteinase-1, -3 and -9 proteins (MMP-1, -3, -9). Human chondrocytes were cultured on collagen type-II-coated petri dishes, exposed to IL-1beta and treated with or without Hox alpha and 13-HOTrE. A close analysis by immunofluorescence microscopy and western blot analysis showed that Hox alpha and 13-HOTrE significantly suppressed IL-1beta-induced expression of matrix metalloproteinase-1, -3 and -9 proteins on the chondrocytes in vitro. The potential of Hox alpha and 13-HOTrE to suppress the expression of matrix metalloproteinases may explain the clinical efficacy of stinging nettle leaf extracts in treatment of rheumatoid arthritis. These results suggest that the monosubstance 13-HOTrE is one of the more active antiinflammatory substances in Hox alpha and that Hox alpha may be a promising remedy for therapy of inflammatory joint diseases.

NO inhalation reduces pulmonary arterial pressure but not hemorrhage in maximally exercising horses.

In horses, the exercise-induced elevation of pulmonary arterial pressure (Ppa) is thought to play a deterministic role in exercise-induced pulmonary hemorrhage (EIPH), and thus treatment designed to lower Ppa might reasonably be expected to reduce EIPH. Five Thoroughbred horses were run on a treadmill to volitional fatigue (incremental step test) under nitric oxide (NO; inhaled 80 ppm) and control (N(2), same flow rate as per NO run) conditions (2 wk between trials; order randomized) to test the hypothesis that NO inhalation would reduce maximal Ppa but that this reduction may not necessarily reduce EIPH. Before each investigation, a microtipped pressure transducer was placed in the pulmonary artery 8 cm past the pulmonic valve to monitor Ppa. EIPH severity was assessed via bronchoalveolar lavage (BAL) 30 min postrun. Exercise time did not differ between the two trials (P > 0.05). NO administration resulted in a small but consistent and significant reduction in peak Ppa (N(2), 102.3 +/- 4.4; NO, 98.6 +/- 4.3 mmHg, P < 0.05). In the face of lowered Ppa, EIPH severity was significantly higher in the NO trial (N(2), 22.4 +/- 6.8; NO, 42.6 +/- 15.4 x 10(6) red blood cells/ml BAL fluid, P < 0.05). These findings support the notion that extremely high Ppa may reflect, in part, an arteriolar vasoconstriction that serves to protect the capillary bed from the extraordinarily high Ppa evoked during maximal exercise in the Thoroughbred horse. Furthermore, these data suggest that exogenous NO treatment during exercise in horses may not only be poor prophylaxis but may actually exacerbate the severity of EIPH.

Respiratory muscle blood flows during physiological and chemical hyperpnea in the rat.

Whether the diaphragm retains a vasodilator reserve at maximal exercise is controversial. To address this issue, we measured respiratory and hindlimb muscle blood flows and vascular conductances using radiolabeled microspheres in rats running at their maximal attainable treadmill speed (96 +/- 5 m/min; range 71-116 m/min) and at rest while breathing either room air or 10% O(2)-8% CO(2) (balance N(2)). All hindlimb and respiratory muscle blood flows measured increased during exercise (P < 0.001), whereas increases in blood flow while breathing 10% O(2)-8% CO(2) were restricted to the diaphragm only. During exercise, muscle blood flow increased up to 18-fold above rest values, with the greatest mass specific flows (in ml. min(-1). 100 g(-1)) found in the vastus intermedius (680 +/- 44), red vastus lateralis (536 +/- 18), red gastrocnemius (565 +/- 47), and red tibialis anterior (602 +/- 44). During exercise, blood flow was higher (P < 0.05) in the costal diaphragm (395 +/- 31 ml. min(-1). 100 g(-1)) than in the crural diaphragm (286 +/- 17 ml. min(-1). 100 g(-1)). During hypoxia+hypercapnia, blood flows in both the costal and crural diaphragms (550 +/- 70 and 423 +/- 53 ml. min(-1). 100 g(-1), respectively) were elevated (P < 0.05) above those found during maximal exercise. These data demonstrate that there is a substantial functional vasodilator reserve in the rat diaphragm at maximal exercise and that hypoxia + hypercapnia-induced hyperpnea is necessary to elevate diaphragm blood flow to a level commensurate with its high oxidative capacity.

Effects of antihypertensive drugs on cholesterol metabolism of human mononuclear leukocytes and hepatoma cells.

OBJECTIVES: Primary prevention trials of antihypertensive therapy have shown conflicting results on coronary events. Potential interference of antihypertensive agents with cellular lipid metabolism may alter the atherosclerotic risk of individuals. DESIGN AND METHODS: The effects of the calcium antagonist's verapamil, diltiazem, and nifedipine and of the beta-blockers propranolol and metoprolol on low density lipoprotein (LDL) receptor activity, cholesterol esterification rate, oleate incorporation in triglycerides and sterol synthesis were studied in freshly isolated human leukocytes and HEP G2 cells. RESULTS: Up to a concentration of 3-10 mumol/L, verapamil, propranolol, and metoprolol led to an increased cellular content of 125I-LDL by an inhibition of degradation. In mononuclear cells verapamil stimulated accumulation and degradation. No effect on binding was observed. Diltiazem was only stimulatory on 125I-LDL processing in leukocytes. Beta blockers and verapamil significantly reduced the LDL mediated 14C-oleate incorporation in cholesterol esters. In the presence of 25-hydroxycholesterol the esterification was not diminished, which suggests that cholesterolacyltransferase (ACAT) was not affected per se. Whereas all the agents induced the synthesis of lanosterol, metoprolol inhibited cholesterol synthesis. None of the agents had a significant influence on 14C-oleate incorporation in triglycerides, suggesting a specific influence on cholesterol metabolism. CONCLUSIONS: Antihypertensive drugs affect the cholesterol metabolism on a cellular level. Mechanisms are an interference with degradation of LDL and consequent alterations of cholesterol esterification. Using leukocytes as peripheral cells and HEP G2 as a model of human liver, these results may have importance when antihypertensive long-term therapy is conducted for primary or secondary prevention of atherosclerotic complications.

Low molecular thymic peptides stimulate human blood dendritic cells.

Dendritic cells are considered to be the most potent antigen-presenting cells and are thus promising new tools for the immunotherapy of cancer. They respond to various stimuli by differentiation (expression of CD83) and up-regulation of costimulatory surface molecules. Thymic peptides have immunostimulatory and immunomodulating properties. Their therapeutic potential in immunotherapy of cancer has been discussed. To test whether thymic peptides act on dendritic cells, we examined the effects of a standardized thymic peptide preparation on cultured human monocyte-derived dendritic cells. Addition of thymic peptides resulted in enhanced expression of the specific differentiation marker CD83 in a dose dependent manner. Moreover, thymic peptides induced the up-regulation of costimulatory molecules including CD86, CD80, HLA-DR and HLA-ABC. After priming with thymic peptides dendritic cells showed an enhanced expression of IL-8 and TNF-alpha mRNA and protein release. Dendritic cells stimulated with thymic peptides were able to induce proliferation of autologous T cells as measured by 3H-thymidine incorporation in mixed Lymphocyte reaction. In combination with a low dosage of keyhole limpet hemocyanin, thymic peptides showed additive effects in the up-regulation of CD83 and costimulatory surface markers. Our findings indicate that thymic peptides per se act on professional antigen-presenting cells in a stimulatory manner and were presented by these cells. Furthermore, thymic peptides enhance the response of dendritic cells to low dosages of a standard nominal antigen. Therefore, thymic peptides could improve the immunological activity especially against low amounts of endogenous antigens.

The recombinant human histones H1 zero and H1.2 cause different toxicity profiles on the human leukemia cell line K562.

The human histones H1 zero and H1.2 were expressed in E. coli and purified to homogenity. Their cytotoxicity on the human leukemia cell line K562 and on PBMC from healthy volunteers was compared with the cytotoxic effect of a bovine histone H1 preparation. In this preparation, histone H1.2 was identified as the main compound. All three histone preparations induced a significant dose-dependent toxicity on the leukemia cell line. Compared with the recombinant histone H1 zero, the bovine preparation and recombinant H1.2 showed stronger cytotoxicities. Cytotoxic effects on K562 cells were observed immediately after addition of the histones, whereas the histone preparations failed to induce significant cytotoxicity on PBMC during the first hour of incubation. However, after 24 hours all three histone preparations induced toxic effects on PBMC which were comparable to those observed on the leukemia cell line.