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.     

Reproductive periodicity of the sparid,Acanthopagrus pacificus,on a hierarchy of temporal scales

The reproductive periodicity of the sparid, Acanthopagrus pacificus, over four temporal scales is described. Acanthopagrus pacificus had a short spawning season between June and September, and within this, a peak reproductive period from July to early September. During the peak period there were several spawning peaks corresponding to a lunar periodicity, with intense reproductive activity on new and full moons that peaked during the period of the full moon when the tidal range was greatest. At the smallest temporal scale, spawning occurred at night on ebb tides. Because this study draws on data collected in 1991 and 1995, it provides a useful baseline against which to judge future changes in reproductive periodicity.     

Heterogeneous periodicity of drosophila mtDNA: new refutations of neutral and nearly neutral evolution

We found a consistent 3-site periodicity of the X29 values for the heterogeneity of the distribution of the second base in relation to the first base of dinucleotides separated by 0 (contiguous), 1, 2, 3 ... 17 (K) nucleotide sites in Drosophila mtDNA. Triplets of X29 values were found where the first was over 300 and the second and third ranged between 37 and 114 (previous studies). In this study, the periodicity was significant until separation of 2011K, and a structure of deviations from randomness among dinucleotides was found. The most deviant dinucleotides were G-G, G-C and C-G for the first, second and third element of the triplet, respectively. In these three cases there were more dinucleotides observed than expected. This inter-bases correlation and periodicity may be related to the tertiary structure of circular DNA, like that of prokaryotes and mitochondria, to protect and preserve it. The mtDNA with 19.517 bp was divided into four equal segments of 4.879 bp. The fourth sub-segment presented a very low proportion of G and C, the internucleotide interaction was weaker in this sub-segment and no periodicity was found. The maintenance of this mtDNA structure and organization for millions of generations, in spite of a high recurrent mutation rate, does not support the notion of neutralism or near neutralism. The high level of internucleotide interaction and periodicity indicate that every nucleotide is co-adapted with the residual genome.     

Seasonal changes in the white blood cell system, lyzozyme activity and cortisol level in Arabian brood mares and their foals

In 34 pure-breed Arabian horses divided into four groups (Gr. I, ten pregnant mares; Gr. II, seven barren mares; Gr. III, ten foals born in 1981; Gr. IV, seven foals born in 1982) seasonal changes in the white blood cell system, cortisol level and lyzozyme activity were studied. Seasonal periodicity was found in all groups for the number of lymphocytes, segmented neutrophils and eosinophils and cortisol level. Leukocyte periodicity was found in three groups, but not in the barren mares. In lyzozyme activity there was periodicity in three groups but not in the youngest foals. In the stab neutrophils, basophils and monocytes no cycle was observed. The behaviour of the indices studied showed the influence of age of the horses (mature vs young) and the physiological state of the mares (pregnancy or barrenness).     

Identification of amino acid latent periodicity within 94 protein families.

Here, we have applied information decomposition, cyclic profile alignment, and noise decomposition techniques to search for latent repeats within protein families of various functions. We have identified 94 protein families with a family-specific periodicity. In each case, the periodic element was found in greater than 70% of family members. Latent periodicity profiles with specific length and signature were obtained in each case. The possible relationship between the periodic elements thus identified and the evolutionary development of the protein families are discussed with specific reference to the possibility that there is a correlation between the periodic elements and protein function.     

Classification of triplet periodicity in DNA sequences of genes taken from KEGG databank

We conducted classification for 472,288 regions of triplet periodicity found in 578,868 genes from release 29 of KEGG databank. A new concept of triplet periodicity class and a measure of similarity between them are introduced. Totally 2520 classes were created that contain 94% of found triplet periodicity. For 92% of triplet periodicity regions contained in classes an identical linkage of triplet periodicity to reading frame is observed. For the rest triplet periodicity cases a shift between reading frame of a gene and reading frame common for majority of genes contained in a class of triplet periodicity was observed. These periodicity regions were encoded into hypothetical amino acid sequences in accordance with reading frame built by triplet periodicity class. By BLAST program it was shown that 2660 hypothetical amino acid sequences have statistically significant similarity with proteins from UniProt databank. We suppose that 8% of triplet periodicity regions that joined classes mutated by means of reading frame shift. Created classes of triplet periodicity can be used for identification of coding regions of genes as well as for searching for mutations arisen from reading frame shift.     

Classification of triplet periodicity in the DNA sequences of genes from KEGG databank

Totally, 472 288 regions of triplet periodicity were found in 578 868 genes from KEGG databank version 29 and classified. A new concept of triplet periodicity class and a measure of similarity between periodicity classes were introduced. Overall, 2520 classes were created and contained 94% of the triplet periodicity cases found. A similar correlation between the triplet periodicity and reading frame was observed for 92% of triplet periodicity regions contained in different classes. The remaining triplet periodicity regions displayed a shift of the reading frame relative to that common for the majority of genes belonging to the same triplet periodicity class. The hypothetical amino acid sequences were deduced from the periodicity regions according to the reading frame characteristic of the given triplet periodicity class. BLAST analysis demonstrated that 2660 hypothetical amino acid sequences display a statistically significant similarity to proteins from the Uni-Prot databank. It was supposed that 8% of the triplet periodicity regions contained in the classes have frameshift mutations. The triplet periodicity classes can be used to identify the coding regions in genes and to searching for frameshift mutations.     

Effect of octreotide on 24-hour growth hormone and prolactin secretory patterns in acromegalics.

Four adult patients with active acromegaly underwent studies of their 24-hour secretory pattern of hGH and Prl prior to and at the end of 3 months of treatment with the octreotide (somatostatin analog SMS 201-995) 100 micrograms s.c. every 8 h. Blood was withdrawn at 30-min intervals with the aid of a constant withdrawal pump. The best fit cosinor method was used to define the following rhythm parameters: mesor, amplitude, acrophase and periodicity. Prior to treatment, hGH secretion was increased in all patients. The mean 24-hour ranged from 9-47 ng/ml with amplitude 5.2-23 and observed maximal pulse 41-95 ng/ml. Computed rhythms were circadian in 3 patients and ultradian in 1; in 2 patients the acrophases were shifted to daytime. hPrl secretion was altered in 3 of the patients. Two had elevated mean 24-hour of 17.7 and 22.2 ng/ml, while computed rhythms showed semicircadian periodicity in 1 of them and circadian periodicity with a shift of acrophase to daytime in the other. The third patient who had normal hPrl levels, showed ultradian 8-hour periodicity. At the end of treatment there was a marked reduction in hGH secretion in 1 patient and a lesser reduction in the other 3. The rhythm was influenced by the masking effect of the drug, to yield an 8-hour period with acrophases related to injection clock time having equal amplitudes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Periodicity in prokaryotic and eukaryotic genomes identified by power spectrum analysis

We used a power spectrum method to identify periodic patterns in nucleotide sequence, and characterized nucleotide sequences that confer periodicities to prokaryotic and eukaryotic genomes and genomes. A 10-bp periodicity was prevalent in hyperthermophilic bacteria and archaebacteria, and an 11-bp periodicity was prevalent in eubacteria. The 10-bp periodicity was also prevalent in the eukaryotes such as the worm Caenorhabditis elegans. Additionally, in the worm genome, a 68-bp periodicity in chromosome I, a 59-bp periodicity in chromosome II, and a 94-bp periodicity in chromosome III were found. In human chromosomes 21 and 22, approximately 167- or 84-bp periodicity was detected along the entire length of these chromosomes. Because the 167-bp is identical to the length of DNA that forms two complete helical turns in nucleosome organization, we speculated that the respective sequences may correspond to arrays of a special compact form of nucleosomes clustered in specific regions of the human chromosomes. This periodic element contained a high frequency of TGG. TGG-rich sequences are known to form a specific subset of folded DNA structures, and therefore, the sequences might have potential to form specific higher order structures related to the clustered occurrence of a specific form of the speculated nucleosomes.     

Synchronicity,periodicity and bimodality in inter‐annual tree seed production along an elevation gradient

Distinctive inter‐annual patterns of tree seed production can include spatial synchronicity, periodicity, and high variability among individuals within a population. Synchronicity and high variability are now commonly used to define mast seeding, with ‘strict’ mast seeding further distinguished by annual seed production that is either often large or nil and thus bimodal. Here we test for synchronicity, periodicity, and bimodality using 43 years of annual total and viable seed counts, along four transect lines, sampling an elevation gradient (480–1340 m) in a monospecific New Zealand mountain beech Nothofagus solandri var. cliffortioides forest. We expect most support for periodicity and bimodality at relatively high elevation sites that are most resource limited and known to have the greatest variability in seed production. While there was weak evidence for differences in viable seed counts along the elevation gradient, this was not the case for total seed counts. A significant year‐effect on seed counts provided some evidence for synchronization, but the correlations of total or viable seed counts rapidly declined (from 0.96 to 0.58) with increasing elevation difference among transect lines. Although we detected a seven‐year periodicity in total and viable seed counts at each elevation, we also detected other period lengths at most elevations. We did not find evidence for our expectation of increased period length and bimodality in relatively unproductive high elevation mountain beech forests because they would take more time to recover from seeding events. As a consequence, if resource limitation is an important driver of mountain beech seed production its influence must be strongly regulated by other factors to determine the distinctive characteristics (periodicity and synchronicity but not bimodality) of inter‐annual variation in seed production.     

Selectivity for harmonic structure in complex sounds by the green treefrog (Hyla cinerea)

1. A psychophysical technique based on reflex modification was used to study the detection of two-tone complexes in background noise by the green treefrog (Hyla cinerea). Three different two-tone complexes were synthesized and presented to measure detection thresholds--a harmonic complex of 900 + 3000 Hz (periodicity of 300 Hz, mimicking the structure of the natural advertisement call); an inharmonic complex of 830 + 3100 Hz; and a second harmonic complex of 828 + 2760 Hz (periodicity of 276 Hz). 2. Masked thresholds and 'critical ratios' (signal-to-noise ratios at threshold) were lowest for the two harmonic complexes (900 + 3000 Hz, mean 'critical ratio' of 16 dB; 828 + 2760 Hz, mean 'critical ratio' of 14 dB). For the inharmonic complex, for which there is no stable first-harmonic periodicity, the mean 'critical ratio' was 24 dB. These data suggest that the green treefrog is sensitive to the harmonic structure of complex sounds as a specific acoustic feature. 3. Because of the unique structure of the treefrog's inner ear, the heightened behavioral sensitivity to harmonic complexes must be due to processing in the central, rather than peripheral, auditory system.     

Geographical variation in the periodicity of gypsy moth outbreaks

The existence of periodic oscillations in populations of forest Lepidoptera is well known. While information exists on how the periods of oscillations vary among different species, there is little prior evidence of variation in periodicity within the range of a single Lepidopteran species. The exotic gypsy moth is an introduced foliage-feeding insect in North America. Its populations are characterized by high amplitude oscillations between innocuously low densities and outbreak levels during which large regions of forests are defoliated. These outbreaks are recognized to arise periodically with considerable synchrony across much of the gypsy moth's North American range. Our analysis indicates that gypsy moth outbreaks in North America are periodic but they exhibit two dominant periodicities: a primary period of 8–10 yr (as previously reported) and a secondary period of 4–5 yr (a new finding in this study). The outbreak periodicity varied geographically and this variation was associated with forest type. We found that in the most susceptible forest types, those on xeric sites where oak is often mixed with pines, outbreak periodicity had a more dominant 5-yr period while in forest types characteristic of more mesic sites where oak was mixed with maples and other species, cycles were clearly operating on a 10-yr period.     

Circadian Periodicity of Serum Prolactin Concentration in Man

Immunoreactive human serum prolactin of pituitary origin has been measured by a radioimmunoassay developed for ovine prolactin. Blood samples were collected at four-hour intervals during a 24-hour period from 12 non-pregnant women, three pregnant women, and seven adult men. A circadian periodicity was found in serum prolactin concentration, with peak values during the night, between 1 a.m. and 5 a.m. for the non-pregnant women, and at 5 a.m. for the adult men. Mean serum levels of prolactin were 1·5 times higher in non-pregnant women than in men. In women investigated during the last month of their pregnancy the mean serum prolactin levels were 2·3 times higher than in the non-pregnant women, but there was no circadian periodicity.     

Several epidemiologic features of the spread of chickenpox and herpes zoster]

Epidemiological and statistical data of herpes zoster and chickenpox by such indices as morbidity level, periodicity and month-by-month changes in the incidence of these diseases were compared. The study included 2345 herpes zoster and 11116 chickenpox cases in the course of 5 years (1972--1976). In comparison with herpes zoster, the intensity of chickenpox spread among the population was on the average 4.7 times greater. Of the total number of chickenpox cases the percentage of herpes zoster contituted 21.0. Chickenpox morbidity had marked seasonal cyclic nature with the amplitude of seasonal variations of about 8; as to herpes zoster--there was no annual or seasonal cyclicity. Thus, in the development of chickenpox and herpes zoster epidemic process there was revealed a peculiar tendency inherent to each of these infections; no common epidemiological and statistical regularities in the spread intensity, annual periodicity and seasonal cyclicity were detected.     

The relationship between number of striae of Retzius and their periodicity in imbricational enamel formation

Imbricational crown formation times (ICFTs) estimated from the number of perikymata on tooth surfaces are error-prone because the number of days between adjacent perikymata varies across individuals and species, and is only visible within tooth microstructure. We investigated striae of Retzius (SR) numbers (analogous to perikymata numbers), SR periodicities (days between SR or perikymata), and ICFTs for a mandibular canine sample (n=49) from medieval Denmark. We tested the relationship between SR number and periodicity to determine whether regression formulae could be produced that would allow periodicity (and ICFTs) to be determined from surface perikymata numbers. Periodicities (range=7-11 days, mode=8) and SR numbers (range=142-257, mean=190.3, s.d.=27.5) were normally distributed; ICFTs were non-normal (mean=1,594 days, s.d.=65.7). We tested periodicity as a quadratic, linear, and log-log transform linear function of SR number and found an inverse relationship (quadratic: R2=0.9504; linear: R2=0.9138; log-log transform: R2=0.9418; all p<0.001) that allowed estimation of periodicity from SR or perikymata numbers in this population and tooth type. If periodicity and SR number are inversely related in other hominin taxa, studies that have estimated ICFT by multiplying perikymata number by a human modal periodicity value or made inferences about development based only on perikymata numbers may have introduced substantial error into their ICFT estimates and life history inferences. The inverse relationship is similar to that predicted by a model of SR formation in which the ICFT for a given tooth type and population is held constant and all combinations of periodicity and SR number result in the same ICFT. However, we found that lower periodicities had longer ICFTs and higher periodicities had shorter ICFTs than the model predicted, suggesting that the model may not reflect the real process, or that there are other factors (e.g., sample size, misclassification, sexual dimorphism) also affecting the relationship between periodicity and SR number.     

Identification of latent periodicity in amino acid sequences of protein families

For detection of the latent periodicity of the protein families responsible for various biological functions, methods of information decomposition, cyclic profile alignment, and the method of noise decomposition have been used. The latent periodicity, being specific to a particular family, is recognized in 94 of 110 analyzed protein families. Family specific periodicity was found for more than 70% of amino acid sequences in each of these families. Based on such sequences the characteristic profile of the latent periodicity has been deduced for each family. Possible relationship between the recognized latent periodicity, evolution of proteins, and their structural organization is discussed.     

The Interference of Flexible Working Times with the Utility of Time: A Predictor of Social Impairment?

Periodic components inherent in actual schedules of flexible working hours and their interference with social rhythms were measured using spectrum analysis. The resulting indicators of periodicity and interference were then related to the reported social impairments of workers. The results show that a suppression of the 24 and the 168 h (seven‐day) components (absence of periodicity) in the work schedules predicts reported social impairment. However, even if there are relatively strong 24 and 168 h components left in the work schedules, their interference with the social rhythm (using the phase difference between working hours and the utility of time) further predicts impairment. The results thus indicate that the periodicity of working hours and the amount of (social) desynchronization induced by flexible work schedules can be used both for predicting the impairing effects of the specific work schedules on social well‐being as well as for the design of socially acceptable flexible work hours.     

The interference of flexible working times with the utility of time: a predictor of social impairment?

Periodic components inherent in actual schedules of flexible working hours and their interference with social rhythms were measured using spectrum analysis. The resulting indicators of periodicity and interference were then related to the reported social impairments of workers. The results show that a suppression of the 24 and the 168 h (seven-day) components (absence of periodicity) in the work schedules predicts reported social impairment. However, even if there are relatively strong 24 and 168 h components left in the work schedules, their interference with the social rhythm (using the phase difference between working hours and the utility of time) further predicts impairment. The results thus indicate that the periodicity of working hours and the amount of (social) desynchronization induced by flexible work schedules can be used both for predicting the impairing effects of the specific work schedules on social well-being as well as for the design of socially acceptable flexible work hours.