Enzymatic characterization of Vibrionaceae strains isolated from environment and cold-blooded animals.

Enzymatic profiles were determined by the API ZYM system for 15 strains of non 01 Vibrio cholerae, 4 strains of V. metschnikovii, 9 strains of V. anguillarum, 6 strains of Plesiomonas shigelloides and 115 strains motile Aeromonas sp. All of the tested strains produced alkaline phosphatase, leucine aminopeptidase and did not possess alpha-fucosidase and alpha-mannosidase. Some differences in enzymatic activities among the tested Vibrionaceae strains were noted. The strains of non 01 V. cholerae, V. metschnikovii, V. anguillarum and P. shigelloides did not produce trypsin, whereas all of the tested Vibrio sp. strains appeared to be positive for this enzyme. Only the strains of P. shigelloides produced BI-Phospho-hydrolase. The lack of acid phosphatase activity was observed among the strains of V. anguillarum.     

The circadian rhythm of heart rate variability

Purpose: In recent years, the measurement of heart rate variability (HRV) has gained ground even outside research settings in everyday clinical and outpatient practice and in health promotion. Methods: Using the search terms “heart rate variability”, “hrv” and “circadian”, a systematic review was carried out in the PubMed database to find original work that analysed the course of HRV parameters over a 24-h period. Results: A total of 26 original studies were found. Almost all the studies detected a circadian rhythm for the HRV parameters analysed. HRV increased during the night in particular and a nighttime peak during the second half of the night was identified. Conclusions: HRV follows a circadian rhythm. But until today, there isn′t any possibility to make quantitative statements about changes over the course of the day for planning short-term measurements. More qualitative studies must be carried in order to close this knowledge gaps.     

A free-running endogenous rhythm of the resting heart rate in man

A sine-wave oscillating rhythm of the heart rate is reported in 24 out of 31 resting healthy subjects. Identification of these free-running cycles was by spectral analysis of minute-by-minute recordings of electrocardiograms, and in a few cases by inspection of cardiotachometer records. The periodicity of this rhythm was circa 10 min and was intermediate in frequency between the rapid fluctuations with frequencies of 15, 30, and 60 s and those of a frequency recurrent every 90 min already described in the literature. Our cycles were independent of age and sex.     

Heart rate monitors and abnormal heart rhythm detection

We test the accuracy of two third generation heart rate monitors (HRM), Accurex Plus and Vantage NV and compare these data with those of an older monitor, PE 4000. Then we investigate responses of the HRM's to abnormal heart rhythms (HR). Accurex Plus and Vantage NV, and PE 4000 were tested in the laboratory under both stable and transient conditions. The Phantom 320 HR simulator gave 7 stable heart rates, each lasting 3 min. The responses of the HRM's to abnormal heart rhythms were tested with an automatic arrhythmia program lasting 17 min. The new HRM's, Accurex Plus and Vantage NV, were more accurate (89 to 94% and over 98% at +/-3 beats per min) in the stable state than the PE 4000. They all showed a smoothing effect in transient measurements, which was stronger in decelerating HR (1st case) than in accelerating HR (2nd case). - 1st case: Accurex Plus =Vantage NV >PE 4000 -2nd case: PE 4000 >Accurex =Vantage. Most isolated heart rhythm disorders (missing beat, pause < 4 s, SVEA, and SVT) were either not detected or rejected. Signal changes such as changes in QRS (ventricular bigeminy) may cause detection losses, and so modify calculated heart rate. HR signal rising/dropping slopes caused by sudden heart rhythm disorders, was notably attenuated, with a consequent loss of HR accuracy. Although the usefulness of HRM's in detecting HR disorders is limited, they have some value with serious disorders, like pause >4 s, important bradycardia or tachycardia.     

Differences in macroglia of the spinal cord in various cold-blooded and warm-blooded animals

Certain macroglial differences of the spinal cord in poikilothermal (Rana esculenta, Lacerta agilis) and in homoiothermal (Columba livia, Felis domesticus, Macaca rhesus) animals have been revealed. A greater amount of glial satellites, surrounding neurons, motor centers of the spinal cord and appearance of new variety of astrocytes and oligodendrocytes are observed in the homoiothermal animals. It is supposed that the phenomenon mentioned indirectly reflects the evolutionary process of a more distinct functional differentiation of macroglia.     

The influence of short-term sedentary behavior on circadian rhythm of heart rate and heart rate variability

The notion that sedentary behavior is harmful to human health is widespread. Little is known about the short term influence of sedentary behavior on heart rate (HR) and heart rate variability (HRV) circadian rhythms. Therefore the purpose of the present study was to examine the influence of short term sedentary behavior on the circadian rhythms of HR and HRV using cosine periodic regression analysis. Sixteen healthy young students were included in a randomized crossover study. All subjects underwent 24-h ECG Holter monitoring in two different states of physical activity, an active condition (more than 15,000 steps per day) and a sedentary condition (less than 1,000 steps per day). Hourly mean values were calculated for HR and HRV, and then were evaluated using cosine periodic regression analysis. The circadian rhythm parameters, amplitude, mesor, and acrophase for HR and HRV variables were obtained. As a result, the significance of the circadian rhythm was confirmed for all variables in each condition. The measure of fit R2 value was decreased in sedentary condition. The amplitude of the sedentary condition was significantly smaller than that of the active condition with respect to HR (7.94 ± 1.91 bpm vs. 15.4 ± 3.93 bpm, p < 0.001), natural log of the high frequency measurement (lnHF) (0.38 ± 0.21 ms2 vs. 0.80 ± 0.28 ms2, p < 0.001), and low frequency/high frequency ratio (LF/HF) (0.75 ± 0.54 vs. 1.24 ± 0.69, p = 0.008). We found that sedentary behavior not only significantly lowered the amplitude of HR and HRV variables, but also might have led to weakness of the circadian rhythm of the HR and HRV variables.     

The size of non-helical regions in collagen I from the skin of cold-blooded animals

The portion of non-spiralized peptide chain in collagen 1 molecules from the skin of cold-blooded animals, such as Arenicola marina, Gadus morhua marisalbi, Eleginus navaga, Rana amurensis, Rana temporaria, Rana semiplicata, Rana ridibunda, Rana dolmatina, Rana graeca, Bombina variegata was determined by recombination-kinetic method. It has been shown that the portion of non-spirilized part of collagen I molecule changes in the animals studied from 2 to 11% and correlates with the temperature of their habitat. There exist also substantial interspecies differences in the collagen I molecule structure.     

Modulation of the heart rate by thyroid hormone in the newborn rat

Confirming the literature data the authors describe that the heart rate is smaller in the newborn rats than in adult ones and increases until the adult values during the first two weeks of life. On the other hand, the blood thyroid hormone exhibits the same pattern, showing an early postnatal increment. As, according the Adolph's data (1967), the heart rate enhancement is not due to the catecholamines, the authors suppose that such enhancement might conceivably depend on thyroid hormone increment.     

Protein synthesis during acclimation of cold-blooded animals to various temperatures]

It was shown that the intensity of protein synthesis in cells of frogs, acclimated to 5 degrees C, is maintained at a high level, which is only 1.5-2 folds lower than that in animals acclimated to 20 C. In the process of acclimation to cold the intensity of synthesis decreases rapidly and already after 5 hours comprises one half of the value, which is characteristic of "warm" frogs, and the intensity of the process decreases more rapidly than the temperature of organs. On acclimation to warmth the intensity of protein synthesis increases and is getting stabilized at the level, characteristic of "warm" amphibia in 10-15 hours. It was shown that under various temperature conditions or conditions of acclimation specific proteins were synthesized against a background of the main groups of proteins.     

The circadian rhythm of selected parameters of heart rate variability

At present, two main circadian oscillators are known, responsible for the rhythm of body temperature (BT) and body activity. Their independence has been demonstrated by the dissociation of these two rhythms in people during long-term isolation. In order to ascertain the circadian rhythm (CR) of heart rate variability (HRV), the ECG was recorded in 24 healthy awake men every two hours in the sitting position, from Friday 5 p.m. to Monday 6 a.m., who were maintained on a standard regime. One hundred consecutive RR intervals in every ECG were measured and from these 11 selected indicators of HRV were computed. Chronograms from the means of BT, respiratory rate, and electrical skin resistance showed pronounced CR with acrophases at 6 to 8 p.m. "Frequency" parameters of HRV, especially the frequency of reversal points, behaved similarly. CR in the remaining 7 "amplitude" parameters was also detected in individual persons, but their acrophases were different, and averaged chronograms mostly exhibited a flat course. The study has shown that there are at least two circadian components of HRV: the first phase has the CR synchronized with BT and is interindividually more homogeneous; the second phase is synchronized with body activity rhythm and is interindividually heterogeneous. On this basis, three equal subgroups of subjects arose, tentatively called afternoon, night, and forenoon types, respectively, in accordance with information about their preference for working and sleeping.     

Estimating the rate of oxygen consumption during submersion from the heart rate of diving animals

How animals manage their oxygen stores during diving and other breath-hold activities has been a topic of debate among physiologists for decades. Specifically, while the behavior of free-ranging diving animals suggests that metabolism during submersion must be primarily aerobic in nature, no studies have been able to determine their rate of oxygen consumption during submersion (Vo(2)d) and hence prove that this is the case. In the present study, we combine two previously used techniques and develop a new model to estimate Vo(2)d accurately and plausibly in a free-ranging animal and apply it to data for macaroni penguins (Eudyptes chrysolophus) as an example. For macaroni penguins at least, Vo(2)d can be predicted by measuring heart rate during the dive cycle and the subsequent surface interval duration. Including maximum depth of the dive improves the accuracy of these predictions. This suggests that energetically demanding locomotion events within the dive combine with the differing buoyancy and locomotion costs associated with traveling to depth to influence its cost in terms of oxygen use. This will in turn effect the duration of the dive and the duration of the subsequent recovery period. In the present study, Vo(2)d ranged from 4 to 28 ml.min(-1).kg(-1), indicating that, at least as far as aerobic metabolism was concerned, macaroni penguins were often hypometabolic, with rates of oxygen consumption usually below that for this species resting in water (25.6 ml.min(-1).kg(-1)) and occasionally lower than that while resting in air (10.3 ml.min(-1).kg(-1)).