Rythmes circannuels chez les mammifères hibernants sauvages

1985 ◽  
Vol 63 (3) ◽  
pp. 453-463 ◽  
Author(s):  
B. Canguilhem
Keyword(s):  
Circadian Rhythms ◽  
Great Variability ◽  
External Factors ◽  
Temperature Changes ◽  
Astronomical Time ◽  
Species Being ◽  
Species Ecology

Circannual rhythms have been studied for 25 years. Most information has come from work on hibernators. Like circadian rhythms, circannuals rhythms are endogenous, innate, self sustained, and their spontaneous frequencies (biological period) are always different from astronomical time. They are insensitive to temperature changes. Their mechanisms are not yet known. Circannual rhythms are synchronized by external factors. There is, however, a great variability among these rhythms, some species being better synchronized than others. Differences in species ecology could be involved in this variability. The adaptative value of these rhythms is discussed.

scholarly journals Morphological diversity of pollen from selected species of the genus Taraxacum, according to their ploidal level

2012 ◽  
Vol 61 (1) ◽  
pp. 65-69 ◽  
Author(s):  
Jolanta Marciniuk ◽  
Anna Rudzińska-Langwald
Keyword(s):  
Pollen Grains ◽  
Morphological Diversity ◽  
Great Variability ◽  
2N Pollen ◽  
Regular Type ◽  
Unknown Number ◽  
Species Being ◽  
The Way

The study of the morphology of pollen concerned eight species of the genus <i>Taraxacum</i>. Seven types were chosen with a different number of chromosomes belonging to the section <i>Palustria</i>: <i>Taraxacum paucilobum</i> 2n = 3x = 24, <i>T. subdolum</i> 2n = 3x =24, <i>T. subpolonicum</i> 2n =3x = 24, <i>T. vindobonense</i> 2n = 4x = 32, <i>T. trilobifolium</i> 2n = 4x = 32, <i>T. mendax</i> 2n = 5x = 40, <i>T. portentosum</i> 2n =? and one type from the section <i>Obliqua</i> - <i>T. platyglossum</i> 2n =?. Pollen from all the examined species was observed by SEM microscopy. A distinct relation exists between the morphology of pollen and the way of reproduction. Pollen of triploidal species, being compulsory apomicts, is characterized by a great variability of the size and a high percentage of deformed pollen grains. Tetraploids, being optional apomicts, produce regular pollen with a relatively even size. The regular type of pollen in pentaploidal <i>Taraxacum mendax</i> and in species with an unknown number of chromosomes (<i>Taraxacum portentosum</i> and <i>T. platyglossum</i>) suggests that these taxa are optional apomicts.

scholarly journals LAJU RESPIRASI INDUK IKAN BLACKHEAD SEABREAM Acanthopagrus schlegelii PADA SUHU PEMELIHARAAN YANG BERBEDA

2017 ◽  
Vol 12 (2) ◽  
pp. 161
Author(s):  
Vitas Atmadi Prakoso ◽  
Young Jin Chang
Keyword(s):  
Body Weight ◽  
Metabolic Rate ◽  
Respiration Rate ◽  
External Factors ◽  
Aquatic Animal ◽  
Marine Fish Species ◽  
Temperature Changes ◽  
Acanthopagrus Schlegelii ◽  
Close Relationship ◽  
Set Up

Laju respirasi hewan akuatik memiliki hubungan yang erat dengan metabolisme. Tingkat metabolisme hewan merupakan variabel yang dapat dipengaruhi faktor dalam maupun luar, salah satunya adalah suhu. Pada ikan, proses metabolisme juga berkorelasi dengan suhu. Salah satu jenis ikan yang perlu dikaji laju respirasinya adalah ikan blackhead seabream Acanthopagrus schlegelii yang merupakan spesies ikan laut yang popular di Korea Selatan, sehingga diperlukan lebih banyak informasi lagi mengenai laju respirasi ikan ini untuk mengoptimalkan metabolisme ikan ini dan berdampak kepada produktivitas budidaya. Penelitian ini bertujuan untuk mengevaluasi laju respirasi induk ikan blackhead seabream pada beberapa tingkatan suhu. Ikan blackhead seabream (panjang total 29,3 ± 2,2 cm dan bobot tubuh 538,3 ± 43,0 g) diteliti menggunakan respirometer dalam sistem resirkulasi. Tiga kelompok percobaan dilakukan untuk mengukur laju respirasi berdasarkan perubahan suhu pemeliharaan (15°C, 20°C, dan 25°C). Hasil penelitian menunjukkan bahwa kecenderungan laju respirasi meningkat secara linier dengan peningkatan suhu perlakuan, dengan nilai tertinggi sebesar 164,8 ± 30,7 mg O2/kg/jam pada 25°C dan nilai terendah sebesar 72,4 ± 8,1 mg O2/kg/jam pada 15°C. Sementara itu, frekuensi pernapasan berkorelasi positif terhadap kenaikan suhu. Berdasarkan penelitian ini, dapat disimpulkan bahwa perubahan suhu dari 15°C ke 25°C menyebabkan peningkatan laju respirasi pada induk ikan blackhead seabream.It is well known that a close relationship exists between respiration rate and metabolism in aquatic animal. In fish, the metabolic rate is influenced by internal or external factors, such as temperature. This research observed the respiration rate of blackhead seabream, Acanthopagrus schlegelii, which is one of the popular marine fish species in South Korea. Despite the fish popularity, very few information are available about the fish’s respiration rate which is important in order to optimize its metabolism and increase its aquaculture productivity. This study aimed to evaluate the respiration rate of adult blackhead seabream reared in media with different temperature settings. The fish (total length of 29.3 ±2.2 cm and body weight of 538.3 ± 43.0 g) were observed using a respirometer placed inside the recirculation systems. Three groups of experiments were set up to measure the fish’s respiration rate according to different rearing temperatures (15°C, 20°C, and 25°C). The results showed that there was a tendency of respiration rate increased linearly with the increase of temperature. The highest respiration rate was 164.8 ± 30.7 mg O2/kg/hour at 25°C and the lowest value was 72.4 ± 8.1 mg O2/kg/hour at 15°C which indicated that the respiratory rate positively correlated to the change in temperature. According to this study, it can be concluded that temperature changes from 15°C to 25°C led an increase in respiration rate of adult blackhead seabream  

scholarly journals Chronobiology and meal times: internal and external factors

1997 ◽  
Vol 77 (S1) ◽  
pp. S29-S38 ◽  
Author(s):  
Jim Waterhouse ◽  
D. Minors ◽  
G. Atkinson ◽  
D. Benton
Keyword(s):  
Food Intake ◽  
Circadian Rhythms ◽  
External Factors ◽  
Ultradian Rhythms ◽  
Internal Factors ◽  
Sleep Period ◽  
Internal And External Factors ◽  
Special Circumstances ◽  
The Brain ◽  
Homeostatic Mechanisms

Although homeostatic mechanisms remain of utmost importance, rhythmic changes are present also. The main ones have a period of 24 h (circadian) or about 2–3 h (ultradian). Circadian rhythms are derived from a body clock, found in the base of the brain, and from the pattern of our sleep wake cycle, including activity and meal times. These rhythms promote the regular changes between an active wake period and a recuperative sleep period. Ultradian rhythms are also widespread and reflect external (lifestyle) and internal factors. The internal factors include biochemical need and some sort of oscillator; but details of how many oscillators, and exactly where they are, remain to be established. Food intake, appetite, digestion and metabolism have been shown to illustrate these principles. Moreover, these principles become important when special circumstances exist as far as meal times are concerned; the particular diffculties of night workers is a good example.

scholarly journals The spliceosome assembly factor GEMIN2 attenuates the effects of temperature on alternative splicing and circadian rhythms

2015 ◽  
Vol 112 (30) ◽  
pp. 9382-9387 ◽  
Author(s):  
Rubén Gustavo Schlaen ◽  
Estefanía Mancini ◽  
Sabrina Elena Sanchez ◽  
Soledad Perez-Santángelo ◽  
Matías L. Rugnone ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Circadian Rhythms ◽  
Clock Genes ◽  
Splicing Factors ◽  
Temperature Changes ◽  
Small Nuclear Ribonucleoprotein ◽  
Assembly Factor ◽  
Effects Of Temperature ◽  
Nuclear Ribonucleoprotein ◽  
Constant Period

The mechanisms by which poikilothermic organisms ensure that biological processes are robust to temperature changes are largely unknown. Temperature compensation, the ability of circadian rhythms to maintain a relatively constant period over the broad range of temperatures resulting from seasonal fluctuations in environmental conditions, is a defining property of circadian networks. Temperature affects the alternative splicing (AS) of several clock genes in fungi, plants, and flies, but the splicing factors that modulate these effects to ensure clock accuracy throughout the year remain to be identified. Here we show that GEMIN2, a spliceosomal small nuclear ribonucleoprotein assembly factor conserved from yeast to humans, modulates low temperature effects on a large subset of pre-mRNA splicing events. In particular, GEMIN2 controls the AS of several clock genes and attenuates the effects of temperature on the circadian period in Arabidopsis thaliana. We conclude that GEMIN2 is a key component of a posttranscriptional regulatory mechanism that ensures the appropriate acclimation of plants to daily and seasonal changes in temperature conditions.

scholarly journals TREND OF AIR TEMPERATURE IN THE STATE OF PARANÁ, BRAZIL (TENDÊNCIA DA TEMPERATURA DO AR NO ESTADO DO PARANÁ, BRASIL)

2016 ◽  
Vol 18 ◽  
Author(s):  
Gabriela Leite Neves ◽  
Jorim Sousa Virgens Filho ◽  
Maysa Lima Leite ◽  
Eliane Nascimento Santos
Keyword(s):  
Air Temperature ◽  
Interpolation Method ◽  
Spline Interpolation ◽  
Statistical Significance ◽  
Great Variability ◽  
The State ◽  
Temperature Changes ◽  
Trend Magnitude ◽  
Daily Data ◽  
Minimum Air Temperature

Considering the importance of climatologic series and the local temperature variability analyses, this study aimed to evaluate the trend of maximum and minimum air temperature in the State of Paraná, Brazil. It were used daily data for the period 1980 to 2009 of 28 locations. The trend magnitude was obtained through linear regression and statistical significance using the Mann-Kendall non-parametric test. The spatial distribution of changes found was represented in geo-referenced maps elaborated through the ARCGIS v.10.0 with the spline interpolation method. The results revealed that the State of Paraná presents great variability in air temperature changes, with differences between places ranging from reductions of 0.5 reductions to increases of 0.6 °C/decade. These increases occurred mainly during the winter and the spring and reductions in the autumn. It was not possible to define simultaneity between the trends due to different changes found, which may be related to local factors such as relief, vegetation and regional activities.

Cryo-TEM of amphiphilic polymer and amphiphile/polymer solutions

1993 ◽  
Vol 51 ◽  
pp. 876-877
Author(s):  
Yeshayahu Talmon
Keyword(s):  
Microstructural Characterization ◽  
Building Blocks ◽  
Quantitative Information ◽  
Physical Models ◽  
Specimen Preparation ◽  
Time Resolved ◽  
Temperature Changes ◽  
Temperature And Humidity ◽  
Microstructured Fluids ◽  
Air Streams

To achieve complete microstructural characterization of self-aggregating systems, one needs direct images in addition to quantitative information from non-imaging, e.g., scattering or Theological measurements, techniques. Cryo-TEM enables us to image fluid microstructures at better than one nanometer resolution, with minimal specimen preparation artifacts. Direct images are used to determine the “building blocks” of the fluid microstructure; these are used to build reliable physical models with which quantitative information from techniques such as small-angle x-ray or neutron scattering can be analyzed.To prepare vitrified specimens of microstructured fluids, we have developed the Controlled Environment Vitrification System (CEVS), that enables us to prepare samples under controlled temperature and humidity conditions, thus minimizing microstructural rearrangement due to volatile evaporation or temperature changes. The CEVS may be used to trigger on-the-grid processes to induce formation of new phases, or to study intermediate, transient structures during change of phase (“time-resolved cryo-TEM”). Recently we have developed a new CEVS, where temperature and humidity are controlled by continuous flow of a mixture of humidified and dry air streams.

An Overview of Dementias

2012 ◽  
Vol 21 (3) ◽  
pp. 75-84
Author(s):  
Venkata Vijaya K. Dalai ◽  
Jason E. Childress ◽  
Paul E Schulz
Keyword(s):  
Clinical Presentation ◽  
Treatment Options ◽  
Current Treatment ◽  
Great Variability ◽  
Health Concern ◽  
Public Health Concern ◽  
Life Threatening ◽  
The Common ◽  
Neurodegenerative Dementias ◽  
Made In

Dementia is a major public health concern that afflicts an estimated 24.3 million people worldwide. Great strides are being made in order to better diagnose, prevent, and treat these disorders. Dementia is associated with multiple complications, some of which can be life-threatening, such as dysphagia. There is great variability between dementias in terms of when dysphagia and other swallowing disorders occur. In order to prepare the reader for the other articles in this publication discussing swallowing issues in depth, the authors of this article will provide a brief overview of the prevalence, risk factors, pathogenesis, clinical presentation, diagnosis, current treatment options, and implications for eating for the common forms of neurodegenerative dementias.

The Biological Clock and Sleep in the Elderly

2006 ◽  
Vol 19 (1) ◽  
pp. 45-51 ◽  
Author(s):  
Myriam Juda ◽  
Mirjam Münch ◽  
Anna Wirz-Justice ◽  
Martha Merrow ◽  
Till Roenneberg
Keyword(s):  
Circadian Rhythms ◽  
Biological Clock ◽  
The Elderly ◽  
Early Morning ◽  
Behavioral Changes ◽  
Older Age ◽  
Age Related ◽  
Theoretical Considerations ◽  
Sleep Difficulties ◽  
Circadian Biology

Abstract: Among many other changes, older age is characterized by advanced sleep-wake cycles, changes in the amplitude of various circadian rhythms, as well as reduced entrainment to zeitgebers. These features reveal themselves through early morning awakenings, sleep difficulties at night, and a re-emergence of daytime napping. This review summarizes the observations concerning the biological clock and sleep in the elderly and discusses the documented and theoretical considerations behind these age-related behavioral changes, especially with respect to circadian biology.

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