Honey bees navigate according to a map-like spatial memory

By using harmonic radar, we report the complete flight paths of displaced bees. Test bees forage at a feeder or are recruited by a waggle dance indicating the feeder. The flights are recorded after the bees are captured when leaving the hive or the feeder and are released at an unexpected release site. A sequence of behavioral routines become apparent: (i) initial straight flights in which they fly the course that they were on when captured (foraging bees) or that they learned during dance communication (recruited bees); (ii) slow search flights with frequent changes of direction in which they attempt to "get their bearings"; and (iii) straight and rapid flights directed either to the hive or first to the feeding station and then to the hive. These straight homing flights start at locations all around the hive and at distances far out of the visual catchment area around the hive or the feeding station. Two essential criteria of a map-like spatial memory are met by these results: bees can set course at any arbitrary location in their familiar area, and they can choose between at least two goals. This finding suggests a rich, map-like organization of spatial memory in navigating honey bees.     

Does the Improvement of Position Sense Following Motor Imagery Practice Vary as a Function of Age and Time of Day?

ABSTRACT

The effectiveness of motor imagery practice is known to depend on age and on the ability to form motor images. In the same individual, motor imagery quality changes during the day, being better late in the morning for older adults and in the afternoon for younger adults. Does this mean that motor imagery practice should be done at specific time of the day depending on the age of participants to maximize motor learning? To examine whether the effect of motor imagery practice varies as a function of time of day and age, the authors used an arm configuration reproduction task and measured position sense accuracy before and after 135 kinesthetic motor imagery trials. Younger and older participants were randomly assigned to either a morning or an afternoon session. Data showed that the accuracy for reproducing arm configurations improved following imagery practice regardless of time of day for both younger and older adults. Moreover, the authors observed that the position sense was less accurate in the afternoon than in the morning in older participants (before and after motor imagery practice), while performance did not change during the day in younger participants. These results may have practical implications in motor learning and functional rehabilitation programs. They highlight the effectiveness of motor imagery practice for movement accuracy in both younger and older adults regardless of time of day. By contrast, they reveal that the assessment of position sense requires that the time of day be taken into account when practitioners want to report on the older patients’ progress without making any mistakes.     

Further evidence on the role of the hypothalamic afferents on the estrogen-induced prolactin release.

Serum prolactin (Prl) concentrations in ovariectomized rats were low without significant differences between morning and afternoon values. These levels were not affected by either frontal or caudal hypothalamic deafferentation. However, they increased after lesioning the hypothalamic median eminence (ME). Three days after the injection of 20 microgram estradiol benzoate (EB) into ovariectomized non-lesioned rats, a rise in serum Prl occurred in the afternoon but not in the morning. In animals with ME lesions estrogen enhanced both morning and afternoon values. The animals with caudal hypothalamic deafferentation and those which had undergone sham operation showed the same pattern as the normal animals. On the contrary, after estrogen treatment of rats with frontal hypothalamic deafferentation high serum Prl concentration during the morning and low levels in the afternoon were observed. It is concluded that estrogen effects on Prl secretion are in part mediated by frontal neural afferents to the hypothalamus. They would facilitate Prl inhibiting factor (PIF) secretion in the morning and inhibit PIF secretion in the afternoon.     

Age and natural metabolically-intensive behavior affect oxidative stress and antioxidant mechanisms

Flying honey bees have among the highest mass-specific metabolic rates ever measured, suggesting that their flight muscles may experience high levels of oxidative stress during normal daily activities. We measured parameters of oxidative stress and antioxidant capacity in highly metabolic flight muscle and less active head tissue in cohorts of age-matched nurse bees, which rarely fly, and foragers, which fly several hours per a day. Naturally occurring foraging flight elicited an increase in flight muscle Hsp70 content in both young and old foragers; however catalase and total antioxidant capacity increased only in young flight muscle. Surprisingly, young nurse bees also showed a modest daily increase in Hsp70, catalase levels and antioxidant capacity, and these effects were likely due to collecting the young nurses soon after orientation flights. There were no differences in flight muscle carbonyl content over the course of daily activity and few differences in Hsp70, catalase, total antioxidant capacity and protein carbonyl levels in head tissue regardless of age or activity. In summary, honey bee flight likely produces high levels of reactive oxygen species in flight muscle that, when coupled with age-related decreases in antioxidant activity may be responsible for behavioral senescence and reduced longevity.     

Limited clinical usefulness of plasma corticotropin-releasing hormone, adrenocorticotropin and beta-endorphin measurements as markers of lung cancer.

We measured plasma corticotropin-releasing hormone (CRH), ACTH, beta-endorphin (beta-EP), and cortisol levels as possible tumor markers in a sequence of 103, randomly selected, patients with lung cancer but without the ectopic Cushing's syndrome and in 72 age- and sex-matched controls. Plasma CRH levels of cancer patients were similar to those of controls both in patients sampled in the morning or in the afternoon. On the other hand, plasma ACTH levels of cancer patients were significantly higher than control patients both in the morning and in the afternoon and showed a preserved circadian rhythm. However, about 35% of cancer patients sampled in the morning and about 60% of those sampled in the afternoon had ACTH levels within the 95% confidence interval (CI) of controls. Also plasma beta-EP levels were more elevated in cancer patients than controls in the morning but about 33% of them and about 80% of those sampled in the afternoon had beta-EP levels within the 95% CI of controls. Despite the higher plasma ACTH levels, cancer patients had cortisol plasma levels similar to controls with preserved circadian rhythm. In conclusion, although mean plasma ACTH and beta-EP were higher in patients affected by lung cancer, their measurements, as well as those of CRH, have practically no diagnostic value. Perhaps measurement of ACTH levels in the bronchial lavage may be more helpful.     

Morning increase in hemodynamic response to exercise in patients with angina pectoris

Summary The present study was conducted to determine whether or not there is diurnal variation in the hemodynamic responses to stimuli that increase myocardial oxygen demand, and the effects of such variation on electrocardiograms (ECG). Fifteen patients with angina pectoris, 17 patients with old myocardial infarction, and 8 healthy controls were examined in this study. Graded exercise stress testing was conducted in the supine position, once in the morning and once in the afternoon, using a bicycle ergometer. A standard 12-lead ECG was recorded before, immediately after, and 3, 5, and 10 min after the end of the exercise. The exercise ECG and blood pressure changes were compared among the groups and, within each group, the results after morning and afternoon exercise were compared. Hemodynamic responses, including heart rate, blood pressure, and the pressure-rate product, showed greater increases in the morning than in the afternoon in angina patients and controls, in association with greater depression of the electrocardiographic ST-segment. In contrast, patients with old myocardial infarction exhibited no difference in hemodynamic responses or the ST-pattern from morning to afternoon. The results suggest that diurnal variation of hemodynamic responses to increased oxygen demand may explain, at least partly, why myocardial ischemia of effort angina is more severe in the morning than in the afternoon.     

Effects of morning hypoglycemia on neuroendocrine and metabolic responses to subsequent afternoon hypoglycemia in normal man

There is general agreement that prior hypoglycemia blunts subsequent hypoglycemic counterregulatory responses. However, there is considerable debate concerning the timing and number of prior hypoglycemic episodes required to cause this blunting effect. The aim of this study was to determine whether one episode of hypoglycemia could modify neuroendocrine, metabolic, and symptom responses to hypoglycemia induced 2 h later. A total of 24 (12 male and 12 female) young, healthy, overnight-fasted subjects participated in a series of glucose clamp studies. A total of 16 individuals underwent 2 randomized studies of either identical 2-h morning and afternoon hyperinsulinemic (490 +/- 60 pmol/L) hypoglycemia (2.9 +/- 0.1 mmol/L) separated by 2 h or, at least 2 months later, 2-h morning and afternoon hyperinsulinemic (492 +/- 45 pmol/L) euglycemia (5.1 +/- 0.1 mmol/L). A total of 8 other subjects participated in a single experiment that consisted of 2-h morning hyperinsulinemic (516 +/- 60 pmol/L) euglycemia (5.1 +/- 0.1 mmol/L) and 2-h afternoon hyperinsulinemic (528 +/- 66 pmol/L) hypoglycemia (2.9 +/- 0.1 mmol/L) also separated by 2 h. Morning hypoglycemia significantly (P < 0.01) reduced (33-55%) the responses of epinephrine, norepinephrine, glucagon, GH, cortisol, and pancreatic polypeptide during afternoon hypoglycemia. Hypoglycemic symptoms (primarily neuroglycopenic) were also significantly (P < 0.01) reduced during afternoon hypoglycemia. Plasma glucose, insulin, nonesterified fatty acids, glycerol, lactate, beta-hydroxybutyrate (P < 0.01), GH, and cortisol (P < 0.05) levels were significantly increased at the start of afternoon hypoglycemia following morning hypoglycemia. Morning hypoglycemia created an insulin-resistant state during afternoon hypoglycemia. Despite blunted neuroendocrine responses, glucose infusion rates required to maintain hypoglycemia and increases in glucose oxidation were significantly attenuated during afternoon compared with morning hypoglycemia. This was in marked contrast to euglycemic control experiments where glucose infusion rates and nonoxidative glucose disposal were significantly increased during afternoon relative to morning studies. We conclude that in normal man one episode of prolonged, moderate, morning hypoglycemia can produce substantial blunting of neuroendocrine and symptomatic responses to subsequent near-term hypoglycemia, and the induction of posthypoglycemic insulin resistance can compensate for blunted neuroendocrine responses by limiting glucose flux and specifically glucose oxidation during subsequent near-term hypoglycemia.     

Incidence and diel pattern of oviposition outdoors of the mosquito, Aedes aegypti (L.) (Diptera: Culicidae) in Trinidad, W.I. in relation to solar aspect

The incidence and diel patterns of oviposition of domestic Aedes aegypti in Trinidad, West Indies during the middle of the wet season (July and August) was compared, using modified ovitraps, in unshaded peridomestic outdoor sites facing east or west. Sites close to each other along a transect differed greatly in the total eggs they received, 18.2% of sites receiving 50.6% of the eggs. Sites receiving most eggs were close to other breeding sites. The incidence of oviposition in sites facing west, as measured by the number of eggs laid (greater than 59%) and by the number of occurrences of eggs (greater than 57%), was greater than in sites facing east. The diel pattern of oviposition was closely similar in sites facing east and west, indicating that the sun's azimuth at the moment of oviposition does not determine whether a female lays in sites facing east or west. The diel pattern of oviposition resembled an earlier study in being bimodal but differed from it in featuring a much larger morning peak (comprising more than 34% of eggs laid v. about 5% in the earlier study). This bimodal pattern closely resembles the diel periodicity of landing on humans described previously by several authors and is probably close to the typical oviposition pattern for Ae. aegypti; an artefact may have modified the oviposition periodicity characterized earlier. In the evening significantly more eggs were laid in sites facing west than in sites facing east. These findings have implications for effective placement of ovitraps for surveillance or suppression of Ae. aegypti, and give rise to an hypothesis which invokes responses to microclimate to account for the form of the bimodal oviposition pattern.     

The significance of direct sunlight and polarized skylight in the ant's celestial system of navigation

As textbook knowledge has it, bees and ants use polarized skylight as a backup cue whenever the main compass cue, the sun, is obscured by clouds. Here we show, by employing a unique experimental paradigm, that the celestial compass system of desert ants, Cataglyphis, relies predominantly on polarized skylight. If ants experience only parts of the polarization pattern during training but the full pattern in a subsequent test situation, they systematically deviate from their true homeward courses, with the systematics depending on what parts of the skylight patterns have been presented during training. This "signature" of the polarization compass remains unaltered, even if the ants can simultaneously experience the sun, which, if presented alone, enables the ants to select their true homeward courses. Information provided by direct sunlight and polarized skylight is picked up by different parts of the ant's compound eyes and is channeled into two rather separate systems of navigation.     

Orthostatic hypotension in the elderly: are the diagnostic criteria adequate?

Orthostatic hypotension (OH) is a common finding in the elderly. OH is defined as a fall of at least 20 mmHg in systolic blood pressure (BP) and/or 10 mmHg in diastolic BP upon assuming an upright posture. Some patients exhibit a fall in BP of less than the defined OH upon standing. The aim of this study was to estimate the prevalence of BP changes not defined as OH among elderly in-patients and to assess the relationship between these changes in the morning and the occurrence of OH during the day. Postural BP measurements were performed in 502 in-patients; in the morning, early afternoon, and in the evening. We defined intermediate postural drop (ID) in BP as a decrease of 10-19 mmHg in systolic BP and/or of 5-9 mmHg in diastolic BP. We observed that OH and ID occurred in 39.2 and 18.5% of the measurements in the morning, respectively. The prevalence of OH and ID was lower in the evening than in the morning (P<0.05) and afternoon (P<0.005). Postural BP changes in the morning correlated with those occurring later in the day. Patients who had ID in the morning had a 57% probability of having OH later during the day. In conclusions, ID is prevalent in elderly in-patients. ID in the morning predicts OH later in the day. Thus, postural BP drops below the OH range may be an important finding in the geriatric population.     

Virtual migration in tethered flying monarch butterflies reveals their orientation mechanisms

A newly developed flight simulator allows monarch butterflies to fly actively for up to several hours in any horizontal direction while their fall migratory flight direction can be continuously recorded. From these data, long segments of virtual flight paths of tethered, flying, migratory monarch butterflies were reconstructed, and by advancing or retarding the butterflies' circadian clocks, we have shown that they possess a time-compensated sun compass. Control monarchs on local time fly approximately southwest, those 6-h time-advanced fly southeast, and 6-h time-delayed butterflies fly in northwesterly directions. Moreover, butterflies flown in the same apparatus under simulated overcast in natural magnetic fields were randomly oriented and did not change direction when magnetic fields were rotated. Therefore, these experiments do not provide any evidence that monarch butterflies use a magnetic compass during migration.     

The stars of low luminosity

A search has been made among the faint stars with large proper motion found on the Palomar Survey plates for objects that, statistically—judging from their magnitude, color, and proper motion—would appear to be fainter than one ten-thousandth of the sun's luminosity. A total of 122 such objects have been found, and an analysis made for solar motion among them does, indeed, indicate that they must be of exceedingly low luminosity.     

Circadian changes in heart rate turbulence parameters

Heart rate turbulence is a novel method to identify patients at risk of cardiac death, and to date, there are no data concerning its circadian changes. In 46 coronary patients (mean age 63 +/- 8 years) with at least 100 ventricular premature beats in 24-hour Holter monitoring, turbulence onset, turbulence slope, and heart rate variability parameters were calculated in 3 equal 4-hour periods during morning, afternoon, and night. No circadian changes in turbulence onset values were found, while TS displayed significantly lower values during afternoon than during morning or night hours (5.08, vs. 7.08 and 7.99 ms/RR, respectively). Some heart rate variability parameters also showed lower values in the afternoon, not in the morning hours. In conclusion, in hospitalized patients with stable coronary artery disease, turbulence slope shows circadian pattern with lowest values observed in the afternoon when compared to morning and night hours.     

Prolactin messenger ribonucleic acid concentrations in 4-day cycling rats and during the prolactin surge

Pituitary PRL mRNA concentrations were measured during the 4-day rat estrous cycle. Adult female Sprague-Dawley rats were killed at 3-h intervals throughout the cycle and hourly between 1000 and 2400 h on proestrus (n = 5-12). Serum PRL was increased on the afternoons of proestrus (P) and estrus (E), with peak concentrations at 1700 h (P, 624 +/- 126; E, 261 +/- 107 ng/ml). PRL mRNA concentrations were elevated during the evening on P and E (2300 h: P, 14.4 +/- 1.5; E, 16.1 +/- 1.3 ng cDNA bound/100 micrograms pituitary DNA) to values 2-fold higher than those at 0800 h on each respective day. On diestrus (D) PRL mRNA levels decreased abruptly during the morning (1100 h, 1.7 +/- 0.3 ng cDNA bound), followed by a 6- to 7-fold increase between 1700 and 2000 h on the same evening. In contrast, PRL mRNA levels were elevated at 0800 h on metestrus (M). The changes in PRL mRNA concentrations obtained on M and D were not associated with increased PRL secretion. A more detailed examination of P revealed that PRL mRNA levels increased during the morning (1000 h, 9.9 +/- 2.6 ng cDNA bound), then decreased abruptly at 1100 h (4.9 +/- 1.2). The morning rise in mRNA concentrations was followed by a 2-fold rise in pituitary PRL content. As serum PRL rose during the afternoon surge, a coincident decrease in pituitary PRL content and an increase in PRL mRNA levels were observed. The relationship between PRL secretion and gene expression was further examined in ovariectomized estradiol-replaced rats receiving either bromocriptine (1.2 mg/day, sc) or vehicle control sc. The vehicle-treated group expressed a characteristic afternoon PRL surge between 1500 and 2100 h. Pituitary PRL decreased during the surge to 10% of morning values, and PRL mRNA levels increased 2-fold beginning 2 h after initiation of the surge. These changes in serum PRL, pituitary PRL, and PRL mRNA levels were abolished by bromocriptine administration. These data reveal that alterations in PRL mRNA concentrations occur on a daily basis during the rat estrous cycle. Increases occur during the evenings of P and E at the time of the increase in PRL secretory activity. The effect of blocking the PRL surge in ovariectomized estradiol-replaced rats suggests a regulatory interaction between secretion and gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)     

The time course and diurnal variation of postural hypotension in diabetic autonomic neuropathy

Nine diabetic patients (age range 23-67y) with autonomic neuropathy and symptomatic postural hypotension were studied. The time course of the postural drop in blood pressure (BP) was documented firstly at 0900h, prior to breakfast and insulin, and secondly in the afternoon. Seven patients were symptomatic in the morning but only one in the afternoon. The systolic nadir in the morning was lower (p less than 0.02) than in the afternoon. The mean systolic pressure in the first 3 min after standing was no different in the afternoon but it was lower in the 2nd (p less than 0.05), 3rd (p less than 0.02), and 4th (p less than 0.02) 3-min intervals in the afternoon. The time taken to reach the systolic nadir was variable, ranging from 1-12 min. It is concluded that the assessment of the postural fall in BP may be underestimated if measured immediately after standing or if it is measured in the afternoon.     

Routine blood pressure measurement: application of the standard canine technique in a human

OBJECTIVE: To examine the effect of applying to human blood pressure readings the standard veterinary method for dogs. DESIGN, SUBJECT AND METHODS: The standard method for dogs uses the mean of five readings after rejection of the initial reading. The canine technique was applied to a human and readings for early morning and afternoon compared on working and non-working days; these values were compared with the single (discarded) reading which started each session. Non-invasive (oscillometric) blood pressure measurements were obtained from the Dinamap 1846 device with printer, set to read automatically at 60 s intervals. RESULTS: The systolic blood pressure was significantly higher on working days, even in the morning, although this would not have emerged from single readings. The diastolic blood pressure was significantly higher during working-day evenings but the heart rate was significantly higher during working mornings. The initial (discarded) reading was significantly higher for systolic but not for diastolic blood pressure. The diastolic results showed greater variation with single readings. Heart rate data did not differ between means and single readings. Systolic and diastolic blood pressures rose significantly during working days but not during non-working days; the heart rate fell during working days. CONCLUSION: Human blood pressure measurements are often based on single readings, even in epidemiological studies. Sensitive monitoring of blood pressure requires a series of readings and allowance for time of day and discrimination between working and non-working days.     

Adrenocortical function in patients investigated for active tuberculosis.

Previous reports have identified adrenal insufficiency in groups of patients with active pulmonary tuberculosis. To investigate this possibility, serum cortisol levels were measured in consecutive patients admitted to the hospital for investigation of active tuberculosis. Blood was drawn for cortisol determination promptly at the time of hospital admission, in the morning and afternoon before commencing chemotherapy for the suspected tuberculosis, and before the diagnosis was confirmed. Thirty-seven patients were assessed; 19 of these patients were subsequently proven to have active pulmonary tuberculosis, six had pulmonary disease caused by mycobacteria other than tuberculosis, and 12 had radiologic appearance indicating tuberculosis, accompanied by a significant tuberculin skin reaction but with negative sputum cultures and no change in roentgenographic appearance during the course of treatment. In evaluating the adrenocortical function, the morning and afternoon serum cortisol level was measured and the diurnal change in serum cortisol level (the difference between afternoon and morning levels) was calculated. There was no association of either morning cortisol levels or diurnal change in cortisol levels with age, gender, or race. There was no difference among the three groups in either cortisol determination. Although difference in morning cortisol levels between those with extensive as compared with limited disease was not statistically significant (p = 0.349 from analysis of variance), there was a significantly decreased diurnal change in cortisol levels in those with extensive disease as compared with those with limited disease (+2.7 +/- 188.3 vs -259.1 +/- 177.1). We conclude that patients in our hospital with active pulmonary tuberculosis do not exhibit decreased adrenocortical function as compared with groups of patients without active pulmonary tuberculosis.     

Gonadal-independent activation of enhanced afternoon luteinizing hormone release during pubertal development in the female rat

In the present study we investigated the extent to which expression of the diurnal pattern of LH secretion in prepubertal female rats is driven by an ovarian-independent neuroendocrine mechanism. To remove gonadal influences, rats were ovariectomized (OVX) during early juvenile, late juvenile, or peripubertal phases of development (20-22, 26-27, and 32-33 days of age, respectively), and blood samples were collected throughout the day (every 30-60 min) 2 or 4 days after surgery. Morning plasma LH levels were relatively low 2 days after ovariectomy (30-120 ng/ml), but rose during the afternoon to reach levels ranging from 180-300 ng/ml. This afternoon elevation was sustained both in late juvenile and peripubertal rats, but not in early juvenile rats. The predominant change observed 4 days after ovariectomy was an overall 3- to 6-fold increase in plasma LH levels, which masked the afternoon elevation. Analysis of plasma LH profiles from individual rats, however, revealed that at each of the three ages studied the peak plasma LH levels occurred in the afternoon, and these were most pronounced in the peripubertal animals. To further clarify the existence of such a diurnal pattern of LH release in the 4-day OVX animals pulsatile LH release profiles were obtained from individual animals, using a 5-min bleeding paradigm, at either 24 days (in the morning) or 36 days of age (in either the morning or the afternoon). LH release was episodic in all of the animals studied, with pulses occurring on average of about once every 30 min. Analysis of the plasma LH profiles using the PULSAR algorithm revealed that the overall mean plasma LH levels of the peripubertal animals was enhanced during the afternoon, compared to that in the morning or to the afternoon LH levels in the early juvenile rats. Mean nadir and mean peak LH levels were also greater. No differences in LH pulse amplitude and only marginal differences in LH pulse frequency were detected among the three groups studied. The enhancement of afternoon LH secretion in the OVX rats could not be attributed to age-related or diurnal changes in adenohypophyseal responsiveness to LHRH. The results suggest that the initiation of enhanced afternoon LH secretion, previously shown to occur in intact female rats during the juvenile-peripubertal transition period, results primarily from the activation of a central neuroendocrine mechanism. Although the ovaries might play a role in the development of this diurnal pattern, it is clear that its activation is ovarian independent.     

Chronopharmacodynamics of delayed-action cardiac glycosides and nitrates

In 96 patients with coronary heart disease and stage II circulatory failure, the chronopharmacodynamics of strophanthin, corglycon, and nitrosorbide was studied by using acute clinical and pharmacological tests in the morning (8.00 a.m.), in the afternoon (2.00 p.m.), and in the evening (8.00 p.m.). Central and peripheral hemodynamic parameters were measured prior to and following 5, 15, 30, 60, and 120 min of intravenous injection of cardiac glycosides or sublingual administration of nitrosorbide in a dose of 10 mg for 240 min. The investigations showed that there were the most profound hemodynamic changes in the morning if strophanthin was used and in the afternoon if corglycon was given. The maximal reduction in heart pre- and afterload was seen in the morning when nitrosorbide was applied, the most improvement in central hemodynamic parameters was observed in the evening when nitrosorbide was used.     

Changes in cellular levels of messenger ribonucleic acid encoding gonadotropin-releasing hormone in the anterior hypothalamus of female rats during the estrous cycle

Cellular levels of messenger RNA encoding GnRH were measured using quantitative in situ hybridization in coronal sections through the area of the organum vasculosum of the lamina terminalis of female rats examined at various times of the 4-day estrous cycle. GnRH mRNA levels were high on the morning of diestrus day 1, but declined throughout the day of diestrus day 2 to a nadir on the morning of proestrus. Although GnRH message levels were lowest on the morning of proestrus, they rose nearly two-fold by 1900h that evening and remained high during the day of estrus. These data support the hypothesis that GnRH synthesis is coupled to GnRH release, and indicate that GnRH biosynthesis is not stimulated on the morning of proestrus in preparation for the ovulatory surge release of GnRH and LH in the afternoon.