Solvatochromism in perylene diimides; experiment and theory.

We report an experimental and computational investigation into the solvatochromism of a perylene diimide derivative. The alkyl swallowtail substituents allowed solubility in many solvents of widely differing polarity, with a complicated resultant behaviour, illustrating both negative and positive solvatochromism as a function of dielectric constant. Luminescence quantum yield and optical absorption linewidth displayed an inverse correlation, indicating varying degrees of intermolecular aggregation, and a remarkably similar trend was found between the peak absorption wavelength and the solvent boiling point, illustrating the dependency of aggregation on the solvent interactions. These outline trends may be parameterised by an empirically derived dimensionless quantity, as a tool to be used in more sophisticated future models of solvatochromism in small molecule chromophores.

Shoaling preference and evidence for maintenance of sibling groups by juvenile black perch Embiotoca jacksoni.

Group sizes in free-living juvenile black perch Embiotoca jacksoni were quantified and predictions of the hypothesis that such groups comprise sibling brood-mates were tested. Group sizes in the field were within the range of female brood sizes and often occurred close to each other but did not merge. In captivity, juveniles formed groups immediately after birth. In laboratory experiments, they also associated significantly more with chambers containing familiar members of their own brood than empty chambers but did not associate more with chambers containing similar-sized juveniles from a different brood. Juvenile E. jacksoni also associated significantly more with chambers containing familiar brood-mates than with chambers containing unfamiliar members of a different brood. The strength of this preference increased with the number of days fish had been together since birth. When two broods were placed in a large outdoor tank, all individuals from both broods directed significantly more aggressive acts towards members of the other brood than towards members of their own brood. While the relative effects of familiarity and relatedness cannot be completely separated in this viviparous species, associating with familiar individuals would facilitate the maintenance of sibling groups in the field.

Thermoregulation is impaired in an environment without circadian time cues.

Squirrel monkeys synchronized to a 24-hour light-dark cycle show a prominent circadian rhythm in body temperature which is regulated against mild environmental cold exposures throughout the 24-hour day. However, cold exposures produce significant decreases in core body temperature when the circadian rhythms of the animal are free-running in the absence of environmental time cues. Effective thermoregulation appears to require the precise internal synchronization of the circadian timekeeping system.

Neurospora circadian rhythms in space: a reexamination of the endogenous-exogenous question.

To test the functioning of circadian rhythms removed from periodicities of the earth's 24-hour rotation, the conidiation rhythm of the fungus Neurospora crassa was monitored in constant darkness during spaceflight. The free-running period of the rhythm was the same in space as on the earth, but there was a marked reduction in the clarity of the rhythm, and apparent arrhythmicity in some tubes. At the current stage of analysis of our results there is insufficient evidence to determine whether the effect seen in space was related to removal from 24-hour periodicities and whether the circadian timekeeping mechanism, or merely its expression, was affected.

A noninvasive analysis of urinary musculoskeletal collagen metabolism markers from rhesus monkeys subject to chronic hypergravity.

A decrease in load-bearing activity, as experienced during spaceflight or immobilization, affects the musculoskeletal system in animals and humans, resulting in the loss of bone and connective tissue. It has been suggested that hypergravity (HG) can counteract the deleterious effects of microgravity-induced musculoskeletal resorption. However, little consensus information has been collected on the noninvasive measurement of collagen degradation products associated with enhanced load-bearing stress on the skeleton. The purpose of this study is to assess the urinary collagen metabolic profiles of rhesus monkeys (Macaca mulatta) during 1) 2 wk of basal 1 G (pre-HG), 2) 2 wk of HG (2 G), and 3) two periods of post-HG recovery (1 G). Urine was collected over a 24-h period from six individual rhesus monkeys. Hydroxyproline (Hyp) and collagen cross-links (hydroxylysylpyridinoline and lysylpyridinoline) were measured by reverse-phase HPLC. Urinary calcium, measured by atomic absorption, and creatinine were also assayed. The results indicate no changes in nonreducible cross-links and Hyp during HG. Collagen cross-link biomarker levels were significantly elevated during the 2nd wk of HG. Urinary calcium content was significantly lower during HG than during the 1-G control period, suggesting calcium retention by the body. We conclude that there is an adaptation of the nonhuman primate musculoskeletal system during hyperloading and that noninvasive measurements of musculoskeletal biomarkers can be used as indicators of collagen and mineral metabolism during HG and recovery in nonhuman primates.

Synthesis and characterisation of new Bi(iii)-containing apatite-type oxide ion conductors: the influence of lone pairs.

Lone-pair cations are known to enhance oxide ion conductivity in fluorite- and Aurivillius-type materials. Among the apatite-type phases, the opposite trend is found for the more widely studied silicate oxide ion conductors, which exhibit a dramatic decrease in conductivity on Bi(iii) incorporation. In this work, the influence of lone-pair cations on the properties of apatite-type germanate oxide ion conductors has been investigated by preparing and characterising seven related compositions with varying Bi(iii) content, by X-ray and neutron powder diffraction and impedance spectroscopy. All materials are very good oxide ion conductors (with conductivities of up to 1.29 × 10-2 S cm-1 at 775 °C). Increasing Bi(iii) content leads to increases in conductivity by up to an order of magnitude, suggesting significant differences in the oxide-ion conduction mechanisms between lone-pair-containing apatite-type germanate and silicate solid electrolytes.

The postnatal development of oxidative metabolism in the suprachiasmatic nucleus of the rat.

This study examined the postnatal development of oxidative metabolism in the rat suprachiasmatic nucleus. The cytochrome oxidase technique was used to reveal the pattern of metabolic development. The cytochrome oxidase reactivity in suprachiasmatic nucleus is above background at birth and coincides with the Nissl-stained borders of the suprachiasmatic nucleus. The suprachiasmatic nucleus gradually increases in cytochrome oxidase intensity through 24 days of age. At 28 days of age the dorsal border in the middle suprachiasmatic nucleus decreases in cytochrome oxidase reactivity. This decrease in cytochrome oxidase reactivity proceeds in a posterior direction until the entire posterior portion of the suprachiasmatic nucleus is devoid of intense cytochrome oxidase reactivity at 42 days of age. Intense cytochrome oxidase was not confined within the Nissl borders of suprachiasmatic nucleus at 28 days of age, but continued laterally beyond the suprachiasmatic nucleus border directly dorsal to the optic chiasm. This lateral region became more intense and extensive through 42 days of age. Therefore, the suprachiasmatic nucleus exhibits a distinct pattern of development in oxidative metabolism. This pattern of metabolic development may be important for understanding the development of overt circadian rhythms.

Evidence for macular gravity receptor modulation of hypothalamic, limbic and autonomic nuclei.

Mice lacking normal vestibular gravity reception show altered homeostatic, circadian and autonomic responses to hypergravity (+G) exposure. Using c-Fos as a marker of neuronal activation, the current study identifies CNS nuclei that may be critical for initiating and integrating such responses to changes in vestibular signaling. This experiment utilized the mutant C57BL/6JEi-het mouse (het), which lacks macular otoconia and thus gravity receptor function. Following 2 h of 2G (2x Earth's gravity) exposure (via centrifugation) the neuronal responses of the het mice were compared with wildtype mice similarly exposed to 2G, as well as het and wildtype 1G controls. Wildtype mice exposed to 2G demonstrated robust c-Fos expression in multiple autonomic, hypothalamic and limbic nuclei, including: the lateral septum, bed nucleus of the stria terminalis, amygdala, paraventricular hypothalamus, dorsomedial hypothalamus, arcuate, suprachiasmatic hypothalamus, intergeniculate leaflet, dorsal raphe, parabrachial and locus coeruleus. The het mice exposed to 2G demonstrated little to null c-Fos expression in these nuclei with a few exceptions and, in general, a similar pattern of c-Fos to 1G controls. Data from this study further support the existence of a complex and extensive influence of the neurovestibular system on homeostatic, circadian and possibly autonomic regulatory systems.

Hemodynamic evaluation of the Monostrut and spherical disc Björk-Shiley aortic valve prosthesis with Doppler echocardiography.

A Doppler echocardiographic study was performed to assess whether the Monostrut model of the Björk-Shiley valve (Shiley, Inc., Irvine, Calif.) had an improved hemodynamic performance in comparison with the spherical disc model in the aortic position. Twenty retrospectively randomly selected patients were studied, 10 with each valve type. Within each valve type two sizes of valve were studied, 21 and 23 mm. The two groups were comparable with respect to age, postoperative time, fractional shortening, New York Heart Association functional class preoperatively, and body surface area. Pulsed and continuous wave Doppler measurements were recorded at rest. Continuous wave Doppler recordings were performed every 2 minutes after exercise with supine bicycle ergometry until 10 minutes after exercise. Peak and mean gradients across the aortic valve prostheses were estimated. Both groups achieved a significant and comparable rise in heart rate with exercise. The mean gradients +/- standard error of the mean at rest and 2 minutes after exercise were 19.7 +/- 1.9 mm Hg and 30.9 +/- 2.2 mm Hg, respectively in the spherical disc group compared with 14.9 +/- 1.1 mm Hg and 23.6 +/- 1.7 mm Hg in the Monostrut group (p < 0.05 and p < 0.025, respectively). Peak transvalvular gradient at rest was 30.7 +/- 2.7 mm Hg in the spherical group compared with 23.9 +/- 1.9 mm Hg in the Monostrut group (p < 0.05). We conclude that the Monostrut Björk-Shiley valve prosthesis has better hemodynamic performance than the spherical disc model in the aortic position.

Effects of 2-G exposure on temperature regulation, circadian rhythms, and adiposity in UCP2/3 transgenic mice.

Altered ambient force environments affect energy expenditure via changes in thermoregulation, metabolism, and body composition. Uncoupling proteins (UCPs) have been implicated as potential enhancers of energy expenditure and may participate in some of the adaptations to a hyperdynamic environment. To test this hypothesis, this study examined the homeostatic and circadian profiles of body temperature (T(b)) and activity and adiposity in wild-type and UCP2/3 transgenic mice exposed to 1 and 2 G. There were no significant differences between the groups in the means, amplitudes, or phases of T(b) and activity rhythms at either the 1- or 2-G level. Percent body fat was significantly lower in transgenic (5.2 +/- 0. 2%) relative to the wild-type mice (6.2 +/- 0.1%) after 2-G exposure; mass-adjusted mesenteric and epididymal fat pads in transgenic mice were also significantly lower (P < 0.05). The data suggest that 1) the actions of two UCPs (UCP2 and UCP3) do not contribute to an altered energy balance at 2 G, although 2) UCP2 and UCP3 do contribute to the utilization of lipids as a fuel substrate at 2 G.

Effects of 2 G on adiposity, leptin, lipoprotein lipase, and uncoupling protein-1 in lean and obese Zucker rats.

Male Zucker rats were exposed to 2 G for 8 wk to test the hypothesis that the leptin regulatory pathway contributes to recovery from effects of 2 G on feeding, growth, and nutrient partitioning. After initial hypophagia, body mass-independent food intake of the lean rats exposed to 2 G surpassed that of the lean rats maintained at 1 G, but food intake of the obese rats exposed to 2 G remained low. After 8 wk at 2 G, body mass and carcass fat were less in both genotypes. Leptin and percent fat were lower in lean rats exposed to 2 G vs. 1 G but did not differ in obese rats exposed to 2 G vs. 1 G. Although exposure to 2 G did not alter uncoupling protein-1 levels, it did elicit white fat pad-specific changes in lipoprotein lipase activity in obese but not lean rats. We conclude that 2 G affects both genotypes but that the lean Zucker rats recover their food intake and growth rate and retain "normal" lipoprotein lipase activity to a greater degree than do the obese rats, emphasizing the importance of a functional leptin regulatory pathway in this acclimation.

Primate circadian rhythms during spaceflight: results from Cosmos 2044 and 2229.

The circadian timing system (CTS) coordinates an animal's physiology and behavior both internally and with the 24-h day. Previous studies have suggested that the CTS is sensitive to changes in gravity. To examine this question, the expression of the CTS in four juvenile male rhesus macaques (Macaca mulatta) were studied in space. These animals were flown on the Cosmos 2044 and 2229 missions. Activity, heart rate, and axillary and brain (Cosmos 2229) temperatures were recorded. In both flights, the subjects exhibited delays in the phasing of their temperature rhythms and a decrease in mean heart rate compared with ground control studies. These data are in support of other studies that demonstrate that the CTS is sensitive to changes in the gravitational environment. Furthermore, the data also support the concept of a multioscillator organization of the primate CTS due to the differential responses of the rhythms measured.

Energy expenditure in rhesus monkeys (Macaca mulatta) during spaceflight using doubly labeled water (2H2(18)O).

The mean daily energy expenditure rates of three rhesus monkeys (Macaca mulatta) were determined during spaceflight on the joint US-Russian Cosmos 2044 and 2229 missions by the doubly labeled water (2H2(18)O) method. In-flight values were compared with ground data obtained from seven measurements taken from six chair-adapted control monkeys. The mean energy expenditure for the ground control determinations was 94.5 +/- 6.4 kcal.kg-1.day-1 (n = 6). The mean in-flight energy expenditure, 55.1 +/- 8.0 kcal.kg-1.day-1 (n = 3), was significantly less than the mean ground control value (P < 0.05). These data suggest that energy expenditure in restrained rhesus monkeys is significantly reduced during spaceflight.

The response of suprachiasmatic neurons of the rat hypothalamus to photic and serotonergic stimulation.

Single-unit activity of the rat suprachiasmatic nucleus and surrounding regions was recorded in vivo. Photically responsive neurons were typically inhibited by low intravenous doses of the serotonin (5-HT) agonist quipazine. The 5-HT antagonist, metergoline, administered in a low intravenous dose, reversed the effects of quipazine. The subsequent response to photic stimulation was essentially identical to the initial photic response. Thus the photic response of neurons in the suprachiasmatic nucleus (SCN) and adjacent regions is relatively uninfluenced by 5-HT blockade.

The retinohypothalamic tract in the cat: retinal ganglion cell morphology and pattern of projection.

The pattern of retinal projection to the hypothalamus and the morphological properties of the retinal ganglion cells that comprise the retinohypothalamic tract have been examined in the cat. Intraocular injections of horseradish peroxidase revealed a dense retinal projection to the ventral suprachiasmatic nucleus; however, lighter projections were seen in the dorsal suprachiasmatic nucleus, and in hypothalamic regions both dorsal and lateral to the suprachiasmatic nucleus. Intrasuprachiasmatic nucleus injections of horseradish peroxidase retrogradely labelled retinal ganglion cells that were small to medium in soma size. The labelled ganglion cells exhibited long thin dendrites that were sparsely branched. The labelled retinal ganglion cells exhibited a significant change in soma size associated with retinal eccentricity. The morphological characteristics of the ganglion cells that project to the suprachiasmatic nucleus are similar to those of gamma cells.

Diurnal modulation of long-term potentiation in the hamster hippocampal slice.

Long-term potentiation (LTP) was examined in hippocampal slices from Syrian hamsters entrained to a LD 14:10 cycle. Population spike (PS) amplitudes from CA1 pyramidal cells were measured before (control) and after tetanizing the Schaffer/collateral commissural pathway. Slices from animals sacrificed during the day, between zeitgeber time (ZT) 0430 and 0530, were incubated, and then tetanized between ZT 1340 and 1930, where ZT=0 denotes lights on. Slices from animals sacrificed during the night, between ZT 1830 and 1930, were incubated, and tetanized between ZT 0030 and 0410. LTP, a sustained increase in PS amplitude following tetanus, was evoked in both groups. PS amplitude increased by 102.7+/-20.3% in animals sacrificed during the day and by 48.0+/-7.5% in animals sacrificed during the night (p<0.05). Thus hamster slices prepared during the day show more robust LTP (a doubling of PS amplitude), a difference persisting in slices incubated for several hours.

Effects of microgravity on brain neurotransmitter receptors.

Neurotransmitter receptor binding and Na+, K+-ATPase activity were examined in the brains of six rats exposed to 7 days of microgravity during the flight of Spacelab 3. The same variables were examined in a group of six ground control rats. 5-HT1 receptor number in the hippocampus was significantly elevated by exposure to the microgravity environment, and cortical sodium-potassium pump activity was significantly depressed. A marginal depression in dopamine D-2 binding in the striatum was noted. Dopamine and 5-HT binding in a wide variety of other central regions, in addition to GABAA, muscarinic acetylcholine, adenosine A1, and opiate receptor binding, and adrenoceptor binding, was unaffected by microgravity exposure.

Effects of light intensity on the circadian temperature and feeding rhythms in the squirrel monkey.

The circadian rhythms of body temperature and feeding appear to be timed by separate pacemakers. Tonic administration of light has been used to investigate the response of the pacemaker timing behavioral rhythms; however, the response of the body temperature rhythm has not been similarly examined. This study investigates the circadian timing of the body temperature rhythm under conditions of different light intensity. We simultaneously recorded the patterns of both feeding and body temperature in squirrel monkeys free-running in an environment free of external time cues. In each lighting condition, the periods of the body temperature and feeding rhythms were identical. In constant bright light the rhythm periods were longer than when the animals were exposed to constant dim light. In addition, the variability of the periods was dependent on light intensity. The feeding rhythm period variance of animals in constant bright light was smaller than when in dim light. Conversely, the period of the free-running body temperature rhythm exhibited more variability in bright light than in dim light. Further, in each condition, there were changes in phase angle relationship between feeding and body temperature which were qualitatively similar to those observed in humans, although quantitatively smaller in magnitude. Thus, in the squirrel monkey, tonic light studies reveal that the mean circadian period of the body temperature and feeding rhythms are similar. However, changes in phase relationship, and differential rhythm period stabilities suggest differences in the period of the underlying, tightly coupled pacemakers.

Role of heat loss and heat production in generation of the circadian temperature rhythm of the squirrel monkey.

To study heat production and heat loss in determination of the daily body temperature rhythm, we examined colonic temperature, skin (tail, foot and abdomen) temperatures and oxygen consumption in chair-restrained squirrel monkeys maintained in isolation in an environmental chamber with a 24-hr light-dark cycle (LD 12:12), maintained at a constant thermoneutral temperature (26 degrees C). In all experiments repeated high amplitude (2 degrees C) diurnal rhythms in colonic temperature were observed. Heat loss, estimated from changes in skin temperature, also displayed a circadian rhythm, although there was considerable variation in waveform. On average, a rhythm in heat production, indicated by changes in the rate of oxygen consumption, was also present. However, a large degree of variability was seen in oxygen consumption, and in several cycles from various animals there were no observable 24-hr rhythms. The circadian body temperature rhythm is thus not simply a consequence of daily changes in metabolism, but rather a regulated response that involves both heat production and heat loss.

Circadian entrainment of the squirrel monkey by extreme photoperiods: interactions between the phasic and tonic effects of light.

To examine the role that the phasic and tonic aspects of the light-dark (LD) cycle play in entraining the circadian timing system of primates, squirrel monkeys (Saimiri sciureus) were exposed to 24 hr LD cycles in which the light duration (photoperiod) was varied from 1 sec to 23 hr. The monkeys were maintained in isolation and the circadian rhythm of drinking was monitored. The photoperiod was first gradually shortened until constant darkness was reached. Even in extremely short photoperiods of only one second of light per day, the drinking rhythm remained synchronized to the 24 hr period of the LD cycle. In the second set of experiments, the photoperiod was gradually lengthened until constant light was achieved. The drinking rhythm of all monkeys was synchronized by 21 hr photoperiods (LD 21:3), but free-ran in 23 hr photoperiods (LD 23:1) which provided a 1 hr dark pulse each day. The tonic effects of light may contribute to the difference between the ability to entrain to short versus long photoperiods. In constant darkness the free-running period was close to 24 hr, thus reducing the phase-resetting necessary to achieve entrainment to a 24 hr period by short light pulses. However, in constant light or in the long photoperiods which did not entrain (LD 23:1) the free-running period of the drinking rhythm was greater than 25 hr, thus requiring a much larger daily phase shift to achieve entrainment to a 24 hr period.