Fundamental and harmonic emission from the rear side of a thin overdense foil irradiated by an intense ultrashort laser pulse

The emission of fundamental and harmonic radiation from the rear side of thin foils in the thickness range 50-460 nm irradiated by intense frequency doubled Ti:sapphire laser pulses of the duration of 150 fs and intensities up to a few 10(18) W/cm(2) was investigated. Following up a previous study of the rear side harmonic emission [Teubner, Phys. Rev. Lett. 92, 185001 (2004)], we measured the emission efficiencies, polarization properties, and the spectral shapes of the fundamental frequency and the second harmonic. Rear side emission is only observed when the obliquely incident laser light is p -polarized. Particle-in-cell (PIC) simulations indicate that the foils remain strongly overdense during the interaction with the laser pulse and that the rear side emission is caused by energetic electron bunches which are generated at the front side by resonance absorption. They are accelerated into the foil and drive strong plasma oscillations at the fundamental and higher harmonic frequencies.

Increased soluble VCAM-1 serum levels in preeclampsia are not correlated to urinary excretion or circadian blood pressure rhythm

OBJECTIVE

Soluble vascular cell adhesion molecule-1 (VCAM-1) is known to be elevated in serum of patients with preeclampsia, but there are no data available on the significance of urinary VCAM-1 excretion in preeclampsia. The aim of our study was to uncover possible circadian rhythms of VCAM-1 plasma levels and urinary VCAM-1 excretion in uncomplicated and hypertensive pregnancies and to ascertain their relation to blood pressure.

STUDY DESIGN

A total of 10 normotensive and 10 preeclamptic pregnant women were included in this study. Venous blood was collected hourly, and urine samples were taken every 2 h over a period of 24 h. VCAM-1 levels were determined by ELISA. We compared these results with the circadian blood pressure rhythm.

RESULTS

The median VCAM-1 plasma levels were significantly (P < 0.01) increased in preeclamptic patients (851.5 ng/mL) in comparison to normotensive pregnant women (659.3 ng/mL) without any circadian rhythm being apparent; however, the urinary excretion of VCAM-1 showed a typical circadian rhythm, with a higher excretion rate during daytime.

CONCLUSION

For the first time we have demonstrated that urinary VCAM-1 excretion in pregnancy shows a circadian rhythm without correlation to plasma levels or the circadian blood pressure rhythm. In contrast, VCAM-1 serum levels did not show a diurnal rhythm. We assume that VCAM-1 serum levels do not correlate with systemic blood pressure or urinary excretion.

Circadian periodicity of cerebral blood flow revealed by laser-Doppler flowmetry in awake rats: relation to blood pressure and activity

Cardiovascular parameters such as arterial blood pressure (ABP) and heart rate display pronounced circadian variation. The present study was performed to detect whether there is a circadian periodicity in the regulation of cerebral perfusion. Normotensive Sprague-Dawley rats (SDR, approximately 15 wk old) and hypertensive (mREN2)27 transgenic rats (TGR, approximately 12 wk old) were instrumented in the abdominal aorta with a blood pressure sensor coupled to a telemetry system for continuous recording of ABP, heart rate, and locomotor activity. After 5-12 days, a laser-Doppler flow (LDF) probe was attached to the skull by means of a guiding device to measure changes in brain cortical blood flow (CBF). After the animals recovered from anesthesia, measurements were taken for 3-4 days. The time series were analyzed with respect to the midline estimating statistic of rhythm (i.e., mean value of a periodic event after fit to a cosine function), amplitude, and acrophase (i.e., phase angle that corresponds to the peak of a given period) of the 24-h period. The LDF signal displayed a significant circadian rhythm, with the peak occurring at around midnight in SDR and TGR, despite inverse periodicity of ABP in TGR. This finding suggests independence of LDF periodicity from ABP regulation. Furthermore, the acrophase of the LDF was consistently found before the acrophase of the activity. From the present data, it is concluded that there is a circadian periodicity in the regulation of cerebral perfusion that is independent of circadian changes in ABP and probably is also independent of locomotor activity. The presence of a circadian periodicity in CBF may have implications for the occurrence of diurnal alterations in cerebrovascular events in humans.

The expression of legumain, an asparaginyl endopeptidase that controls antigen processing, is reduced in endotoxin-tolerant monocytes

The exposition of monocytes to lipopolysaccharide (LPS) primarily causes a massive inflammatory response that is then followed by a hyporesponsive state of these cells. This latter state is called endotoxin tolerance and is characterized by (i) the attenuated production of proinflammatory mediators after repeated LPS treatment, and (ii) the diminished antigen presentation and T-cell stimulation capacity. The data presented here indicate that LPS priming causes a specific decrease in the expression of legumain (the asparaginyl endopeptidase responsible for the key step in antigen processing) in monocytes. In these cells, the fraction of major histocompatibility complex (MHC) class II loaded with CLIP was increased. In contrast to monocytes, LPS priming provoked an increase of legumain expression in B cells. Reduced monocytic expression of legumain was also found in critically ill patients supporting the suitability of endotoxin tolerance as an experimental model of clinical postinflammatory immunodeficiency.

Second order autocorrelation of an XUV attosecond pulse train

Temporal widths of an attosecond (asec) XUV radiation pulse train, formed by the superposition of higher order harmonics, have been recently determined utilizing a 2nd order autocorrelation measurement. An assessment of the validity of the approach, for the broadband XUV radiation of asec pulses, is implemented through ab initio calculations modeling the spectral and temporal response of the two-XUV-photon He ionization detector employed. The measured width of the asec bursts is discussed in terms of the spectral phases of the individual harmonics, as well as in terms of the spatially modulated temporal width of the radiation, and is found in reasonable agreement with the expected duration.

Is there an interaction between interleukin-10 and interleukin-22?

Interleukin(IL)-10 and IL-22 are structurally related cytokines. Their heterodimeric receptors consist of the cytokine-specific chains IL-10R1 and IL-22R1, respectively, and the common chain IL-10R2. This study focused on the question of whether IL-10 modulates IL-22 effects and vice versa. This question is important because IL-10 and IL-22 exert anti- and proinflammatory effects, respectively, and, as we show here, are simultaneously present in both systemic and local inflammation. The revealed lacking concomitance of IL-10R1 and IL-22R1 on identical cells excluded any possible interaction between IL-10 and IL-22 apart from the competition for IL-10R2. To study this competition, monocytes and hepatocytes were chosen. The dependence of the cytokine action on IL-10R2 was verified. Interestingly, no influence of IL-22 on IL-10 effects was observed. The same was true when IL-22 was used in complex with IL-22-binding protein. Similarly, no influence of IL-10 was found on IL-22 action. This missing competition seemed to be due to a lack of binding between IL-10R2 and the native cytokines in the absence of their corresponding R1 chain. However, IL-10R2 interacted with defined IL-10- and IL-22-derived peptides supporting the hypothesis that cytokine binding to its corresponding R1 chain creates a binding site on this cytokine for IL-10R2.

Harmonic emission from the rear side of thin overdense foils irradiated with intense ultrashort laser pulses

The harmonic emission from thin solid carbon and aluminum foils, irradiated by 150 fs long frequency-doubled Ti:sapphire laser pulses at lambda=395 nm and peak intensities of a few 10(18) W/cm(2), has been studied. In addition to the harmonics emitted from the front side in the specular direction, we observe harmonics up to the 10th order, including the fundamental from the rear side in the direction of the incident beam, while the foil is still strongly overdense. The experimental observations are well reproduced by particle-in-cell simulations. They reveal that strong coupling between the laser-irradiated side and the rear side occurs via the nonlocal electron current driven by the laser light.

[Genet(h)ics: the philosophical concept of the discourse ethics and consequences for the research community]

The research community is increasingly confronted with the problem of ethic responsibility. Ethic reflection might be integrated as a part of one's own research projects. This question is discussed against the background of Jürgen Habermas' discourse ethics, which considers the diverse state of being in the modern age as the basis. In this situation, the process of understanding ("Verständigungsprozess") the norms assumed to be valid receives extraordinary significance, since this process of understanding itself inheres authorizing function for the norms. Taking this philosophicial approach seriously, researchers have the specific responsibility not to perform the ethical judgement based on facts alone. Since researchers might be predestined to envisage the ethical implication of their own research at an early stage, they have the possibility to activate the process of understanding about relevant ethical norms themselves as early as possible.

Direct observation of attosecond light bunching

Temporal probing of a number of fundamental dynamical processes requires intense pulses at femtosecond or even attosecond (1 as = 10(-18) s) timescales. A frequency 'comb' of extreme-ultraviolet odd harmonics can easily be generated in the interaction of subpicosecond laser pulses with rare gases: if the spectral components within this comb possess an appropriate phase relationship to one another, their Fourier synthesis results in an attosecond pulse train. Laser pulses spanning many optical cycles have been used for the production of such light bunching, but in the limit of few-cycle pulses the same process produces isolated attosecond bursts. If these bursts are intense enough to induce a nonlinear process in a target system, they can be used for subfemtosecond pump-probe studies of ultrafast processes. To date, all methods for the quantitative investigation of attosecond light localization and ultrafast dynamics rely on modelling of the cross-correlation process between the extreme-ultraviolet pulses and the fundamental laser field used in their generation. Here we report the direct determination of the temporal characteristics of pulses in the subfemtosecond regime, by measuring the second-order autocorrelation trace of a train of attosecond pulses. The method exhibits distinct capabilities for the characterization and utilization of attosecond pulses for a host of applications in attoscience.

High-intensity laser induced ion acceleration from heavy-water droplets

Fusion neutrons from a heavy water droplet target irradiated with laser pulses of 3 x 10(19) W/cm(2) and from a deuterated secondary target are observed by a time-of-flight (TOF) neutron spectrometer. The observed TOF spectrum can be explained by fusion of deuterium ions simultaneously originating from two different sources: ion acceleration in the laser focus by ponderomotively induced charge separation and target-normal sheath acceleration off the target rear surface. The experimental findings agree well with 3D particle-in-cell simulations.

Two-Photon Ionization of He through a Superposition of Higher Harmonics

We present experimental results and theoretical analysis of two-photon ionization of He by a superposition of the 7th to the 13th harmonic of a Ti:sapphire laser. Solving the time-dependent Schrödinger equation for He in a coherent polychromatic field, the He+ yield is calculated. From this yield the number of He+ ions produced has been estimated and found in reasonable agreement with its measured value. The present results establish the feasibility of a second-order autocorrelation measurement of superposition of harmonics, and thus they represent the precursor towards the direct temporal characterization of attosecond pulse trains.

Temporal characterization of short-pulse third-harmonic generation in an atomic gas by a transmission-grating Michelson interferometer

By use of a transmission-grating-based Michelson interferometer, second-order interferometric as well as intensity autocorrelation traces of the third harmonic of a Ti:sapphire 50-fs laser beam produced in Ar have been measured. The duration of the harmonic is found to be that expected from lowest-order perturbation theory. At this wavelength, the performance of the interferometer with respect to pulse-front distortion and dispersion is found to be satisfactory. This result is a first step toward the use of the interferometer for the temporal characterization of higher harmonics or harmonic superposition forming attosecond pulse trains.

MeV ion jets from short-pulse-laser interaction with thin foils

Collimated jets of carbon and fluorine ions up to 5 MeV/nucleon ( approximately 100 MeV) are observed from the rear surface of thin foils irradiated with laser intensities of up to 5 x 10 (19)W/cm(2). The normally dominant proton acceleration could be surpressed by removing the hydrocarbon contaminants by resistive heating. This inhibits screening effects and permits effective energy transfer and acceleration of other ion species. The acceleration dynamics and the spatiotemporal distributions of the accelerating E fields at the rear surface of the target are inferred from the detailed spectra.

Phage-display evolution of tyrosine kinases with altered nucleotide specificity

The problem of identifying downstream targets of kinase phosphorylation remains a challenge despite technological advances in genomics and proteomics. A recent approach involves the generation of kinase mutants that can uniquely use "orthogonal" ATP analogs to phosphorylate substrates in vivo. Using structure-based design, mutants of several protein kinase superfamily members have been found; robust and general methods are needed, however, for altering the nucleotide specificity of the remaining kinases in the genome. Here we demonstrate the application of a new phage display technique for direct functional selection to the identification of a tyrosine kinase mutant with the ability to use N6-benzyl-ATP. Our method produces, in five rounds of selection, a mutant identical to the best orthogonal Src kinase found to date. In addition, we isolate from a larger library of kinase mutants a promiscuous clone capable of using many different ATP analogs. This approach to engineering orthogonal kinases, combined with others, will facilitate the mapping of phosphorylation targets of any kinase in the genome.

Sickness behaviour, an animal equivalent to human quality of life, is improved in septic rats by G-CSF and antibiotic prophylaxis

BACKGROUND AND AIM

New biological response modifiers are usually tested in reductionistic, pharmacological animal models by the determination of mechanistic endpoints (mortality rate, cellular/physiological parameters). In the meantime, quality of life had become an important endpoint in clinical trials but adequate animal experiments are very rare. The aim of this study was to demonstrate alterations in the behavioural response of septic rats due to a prophylaxis with cytokine (G-CSF) plus antibiotics.

METHODS

Sickness behaviour (locomotor activity, circadian rhythms of blood pressure, heart rate and temperature) was determined by the use of radio telemetry. Complex animal experiments in rats were performed including anaesthesia, antibiotic and G-CSF prophylaxis, volume substitution, laparotomy, contamination and infection with human faecal suspension and postoperative analgesia.

RESULTS

Prior to infection, rats showed circadian rhythm in locomotor activity, blood pressure, heart rate and temperature. Sham operation did not alter these parameters significantly. Immediately after abdominal contamination and infection, locomotor activity was strongly reduced and circadian rhythm was lost in all parameters. Body temperature showed a continuous rise, peaking 38 h after infection. Untreated animals died in 63% (8/14) of cases. Antibiotic prophylaxis blunted the febrile response and markedly reduced mortality to 20% (2/10) or 0% (0/10) using G-CSF plus antibiotics. Blood pressure and heart rate were increased in parallel with the rise in temperature. These early physiological changes were not prevented by prophylaxis, but normal behaviour was restored faster with G-CSF plus antibiotic prophylaxis.

CONCLUSIONS

In septic rats, sickness behaviour (locomotor activity) is significantly improved in parallel to the mortality rate by a prophylaxis with G-CSF plus antibiotics. Sickness behaviour can be considered as an equivalent to human quality of life.

Altered melatonin production in TGR(mREN2)27 rats: on the regulation by adrenergic agonists, antagonists and angiotensin II in cultured pinealocytes

Transgenic TGR(mREN2)27 rats (TGR), carrying an additional mouse renin gene, are characterized by severe hypertension, an inverse circadian blood pressure profile, a blunted response to photic entrainment signals, and an increased nocturnal production of the pineal hormone melatonin. In order to evaluate the contribution of the over-expressed renin-angiotensin system to the function of the pineal gland in TGR, we studied the adrenergic and angiotensin II (Ang II)-mediated regulation of melatonin synthesis using dispersed pinealocytes from TGR and from Sprague-Dawley control rats (SDR). Isoproterenol was more effective in stimulating melatonin release in pinealocytes from TGR than from SDR, whereas the maximum effect of norepinephrine (NE) stimulation did not differ between the strains. Prazosin reduced the NE-mediated melatonin release only in SDR but not in TGR pinealocytes. Competition experiments with (+/-)-, (+)-, (-)-propranolol and (+/-)-atenolol revealed one homogeneous population of beta1-adrenoceptors. Ang II had no significant effect on basal or isoproterenol-induced melatonin release in either strain. In conclusion, TGR pinealocytes were more sensitive to beta-adrenergic stimulation than SDR pinealocytes, but lacked the alpha1-adrenergic potentiation of beta-adrenergic induced melatonin release. The renin-angiotensin system was not directly involved in the regulation of melatonin synthesis by rat pinealocytes in vitro.

Addressing cultural orientations in fear appeals: promoting AIDS-protective behaviors among Mexican immigrant and African American adolescents and American and Taiwanese college students

Fear appeals threatening the individual have been shown to be powerful persuasive devices in the cultures where they have been studied. However, most fear appeal research has been conducted with members of individualist cultures. Individualist cultures place self-needs above group concerns, while collectivist cultures place group needs above self-concerns. Little is known about the effectiveness of fear appeals (or other persuasive strategies) in collectivist cultures. Two studies assessed the effectiveness of AIDS-prevention fear appeals threatening the self versus fear appeals threatening the group (i.e., family) on members of individualist and collectivist cultures. The first study focuses on African American and Mexican immigrant junior high school youth. The second study focuses on U.S. and Taiwanese college undergraduates. The results indicated that fear appeals should address cultural orientation (i.e., individualist versus collectivist orientation) to achieve maximum effectiveness. The results also indicate that one cannot assume cultural orientation based on ethnicity.

Day-night variation in the in vitro contractility of aorta and mesenteric and renal arteries in transgenic hypertensive rats

TGR(mREN2)27 (TGR) rats develop severe hypertension and an inverted circadian blood pressure profile with peak blood pressure in the day-time rest phase. The present study investigated the in vitro responsiveness of different arteries of TGR rats during day and night. Twelve-week-old TGR rats and normotensive Sprague-Dawley (SPRD) controls, synchronized to 12h light, 12h dark (LD 12:12) (light 07:00-19:00), were killed at 09:00 (during rest) and 21:00 (during activity), and endothelium-dependent relaxation by acetylcholine and vascular contraction by angiotensin II were studied by measuring isometric force in ring segments of abdominal aorta and mesenteric and renal arteries. In SPRD rats, consistent day-night variation was found, with greater responses to angiotensin II during the daytime rest span. In TGR rats, biological time-dependent differences were found in the renal vasculature, but not in the aorta and mesenteric artery. Relaxation of SPRD rat aorta and mesenteric artery by acetylcholine was greater at 09:00, whereas in TGR rats, day-night variation was absent (mesenteric artery) or inverted (aorta). In conclusion, based on the study of two time points, day-night variation in vascular contractility of aorta and mesenteric artery is blunted in TGR rats, whereas renal artery segments showed an unchanged day-night pattern compared to SPRD controls.

Effect of short light-dark cycles on young and adult TGR(mREN2)27 rats

Animals placed under short light-dark (LD) cycles show a dissociation of their circadian rhythms. However, this effect has only been studied in Wistar rats and with the motor activity (MA) rhythm. Thus, in the present experiment, we studied in TGR(mREN2)27 (TGR) rats, a strain of hypertensive rats, the effect of a short LD cycle on the circadian rhythms of MA, heart rate (HR), and blood pressure (BP). Our aim was (1) to investigate whether the exposure of TGR rats to a short LD cycle induced a dissociation of their circadian rhythms, (2) to study the effect of short LD cycles on the development of the circadian rhythms of TGR rats, and (3) to compare the effect of short LD cycles on young and adult TGR rats. One group of TGR rats was maintained under LD cycles of 22h periods (group G22). The progress in time of their rhythms was compared to that of TGR rats of the same age that had been kept under LD cycles of 24h periods (group G24). For the third point, the rhythms of a group of 5-week-old TGR rats kept under LD 22h cycles (young rats) were compared to those of a group of 11-week-old TGR rats (adult rats). Results showed that there is a dissociation of the circadian rhythms of all the variables monitored in TGR rats maintained under LD 22h cycles, independent of age. We have also found that group G22 showed a higher increase in BP with age and a higher mortality due to malignant hypertension compared to group G24. Finally, it seems that it is harder for young rats to entrain to short LD cycles than for adult rats, and young rats have a higher mortality due to malignant hypertension than adult rats. In conclusion, we demonstrated that short LD cycles produce a dissociation in the HR, BP, and MA circadian rhythms. The results of this experiment, compared to those previously obtained in Wistar rats, suggest that the light perception, the responses of the circadian system to light, or both are altered in the TGR rats.

Circadian pacemaker function and entrainment during maturation of transgenic hypertensive TGR(mREN2)27 and Sprague-Dawley rats

TGR(mREN2)27 (TGR) transgenic rats develop hypertension due to the mouse mRen-2 gene inserted in their genome. At 5 weeks of age, the blood pressure of TGR rats starts rising, until a maximum is reached at 10 weeks of age. Adult TGR rats show peak values of blood pressure (BP) during the light phase, while heart rate (HR) and motor activity (MA) peak at night. In the present experiment, we evaluated the evolution of circadian rhythms in motor activity, heart rate, and blood pressure of TGR and Sprague-Dawley (SD) rats under 12h light-dark cycles (LD 12:12). Results confirmed that the blood pressure of TGR rats starts to increase at 5 weeks of age, reaching a plateau by the 11th week. Parallel to the increase in blood pressure levels, there was a decrease in the period length of the blood pressure rhythm, a delay in the onset of the alpha phase of the blood pressure rhythm with respect to that of motor activity and heart rate, and a decrease in heart rate levels. In all of the variables studied, the alpha phase of SD rats always started before darkness, whereas that of TGR rats started after lights off. In general, heart rate and motor activity levels of TGR rats were higher than those of SD rats. The amplitude of the circadian rhythms studied was greater in TGR rats than in SD rats. The present results suggest that the different evolution of circadian rhythms in TGR and SD rats might be due to differences in the functioning of the entrainment pathway or the circadian clock itself, which can be detected in young rats and that are probably caused by the expression of the mouse transgene.

Non-local-thermodynamical-equilibrium effects in the x-ray emission of radiatively heated materials of different atomic numbers

X-ray self-emission of radiatively heated materials with different values of Z has been investigated. Thin foils were uniformly heated by a 120-eV Hohlraum radiation of 400-ps duration in order to study the self-emission of a homogeneous, optically thin material. The x-ray emission spectra were followed for more than 2 ns. The spectrally integrated emission shows not only a strong Z dependence, but different temporal behaviors for different values of Z. The lower is the value of Z of the x-ray heated matter, the longer is the duration of self-emission. Theoretical comparison with a hydrocode and FLY post-processing shows a non-local-thermal equilibrium behavior caused by direct photoionization due to the thermal pumping radiation, which has a higher brightness temperature than the matter temperature of the heated material.

Chronic heart failure and micronutrients

Heart failure (HF) is associated with weight loss, and cachexia is a well-recognized complication. Patients have an increased risk of osteoporosis and lose muscle bulk early in the course of the disease. Basal metabolic rate is increased in HF, but general malnutrition may play a part in the development of cachexia, particularly in an elderly population. There is evidence for a possible role for micronutrient deficiency in HF. Selective deficiency of selenium, calcium and thiamine can directly lead to the HF syndrome. Other nutrients, particularly vitamins C and E and beta-carotene, are antioxidants and may have a protective effect on the vasculature. Vitamins B6, B12 and folate all tend to reduce levels of homocysteine, which is associated with increased oxidative stress. Carnitine, co-enzyme Q10 and creatine supplementation have resulted in improved exercise capacity in patients with HF in some studies. In this article, we review the relation between micronutrients and HF. Chronic HF is characterized by high mortality and morbidity, and research effort has centered on pharmacological management, with the successful introduction of angiotensin-converting enzyme inhibitors and beta-adrenergic antagonists into routine practice. There is sufficient evidence to support a large-scale trial of dietary micronutrient supplementation in HF.

Cardiovascular regulation in TGR(mREN2)27 rats: 24h variation in plasma catecholamines, angiotensin peptides, and telemetric heart rate variability

Dysfunction of the sympathetic nervous system might play an important role in disturbed 24h blood pressure regulation in transgenic hypertensive TGR (mREN2)27 (TGR) rats. Our study was performed to determine possible differences in activity of the sympathetic nervous system in TGR rats in comparison to their normotensive Sprague-Dawley (SPRD) controls; we measured plasma catecholamine and angiotensin concentrations throughout 24h under synchronized light-dark 12h:12H (LD 12:12) conditions. In the TGR rat strain, rhythms of plasma catecholamines were blunted, and the concentrations were significantly decreased. In addition, TGR rats showed increased plasma angiotensin I and II concentrations without any significant rhythm. An impaired autonomic regulation was confirmed by monitoring heart rate variability in TGR rats. Data showed that the TGR rat strain is characterized by a reduction in plasma catecholamines and an increase in angiotensin peptides. At present, it is not clear whether the reduction in catecholamines represents a decrease in sympathetic tone mediated by baroreflex activation or an increased catecholamine turnover induced by elevated angiotensin II. However, the blunted, but normally phased, rhythms in plasma catecholamines in TGR rats make it unlikely that the sympathetic nervous system is mainly responsible for the inverse circadian blood pressure rhythm in the transgenic strain.

Influence of circadian time and age on glomerular angiotensin II receptors in normotensive Sprague-Dawley and transgenic hypertensive TGR(mREN2)27 rats

In male heterozygous transgenic hypertensive rats, TGR(mREN2)27 (TGR), exhibiting an inverse blood pressure profile and in normotensive Sprague-Dawley (SPRD) controls, the density and affinity of angiotensin II receptors were determined at six circadian times in glomeruli of animals 11 weeks old kept under light-dark 12h:12 (LD 12:12) conditions. Angiotensin II receptors were also studied in rats 18-20 weeks old of both strains at 2h after light onset. As a measure of renal excretory functions, diuresis, creatinine, and protein excretion were monitored using metabolic cages. The expression of angiotensin II receptor mRNA was determined in renal arteries 2h-4h after light onset. The following results were obtained: (1) Renal excretory functions showed significant daily variation, with higher excretion rates in the dark span in both TGR and SPRD rats. (2) No circadian phase dependency was found in the glomerular angiotensin II receptors in both rat strains. However, receptor density was significantly lower in TGR than in SPRD rats. In both strains, receptor number increased with aging. (3) In renal arteries, the angiotensin II receptor mRNA of the main receptor subtype AT1A was neither strain nor age dependent, AT1B- and AT2-receptor mRNAs were significantly lower in TGR than SPRD rats. In conclusion, the results demonstrate that the overactive renin-angiotensin system in TGR rats led to a down-regulation of glomerular angiotensin II receptors that was not accompanied by a down-regulation of the mRNA of the dominant AT1A- receptor subtype. Circadian short-term variations in blood pressure in both TGR and SPRD rats are not reflected by daily variation in angiotensin II receptor density of renal glomeruli or by variation in receptor expression in renal vascular tissue.