Relationship between production of acute-phase proteins and strength of inflammatory stimulation in rats

The relationship between intensity of inflammatory stimulation and production of α(2)-macroglobulin (α2M) and α(1)-acid glycoprotein (AAG) in rats was investigated. Sprague-Dawley rats were injected with turpentine oil at doses of 0.05, 0.2 or 0.4 mL/rat. Serum levels of α2M, interleukin (IL)-6 and cytokine-induced neutrophil chemoattractant-1 (CINC-1) were measured by enzyme-linked immunosorbent assay, and AAG was measured by single radial immunodiffusion. Peak serum levels of α2M and AAG in rats injected at 0.05 mL/rat were significantly lower than those at 0.2 or 0.4 mL/rat. However, no significant differences were observed for peak serum levels of these acute-phase proteins between 0.2 and 0.4 mL/rat. Furthermore, peak serum levels of IL-6 and CINC-1 in rats injected at 0.05 mL/rat were significantly lower than those at 0.2 or 0.4 mL/rat. Thus, the production of these acute-phase proteins has upper limits, even under increased strength of inflammatory stimulation in rats injected with turpentine oil.     

Relationship between temperature and stimulation frequency in conduction block of amphibian myelinated axon

The temperature–frequency relationship in nerve conduction block induced by high-frequency, biphasic electrical current was investigated by computer simulation using an amphibian myelinated axon model based on Frankenhaeuser–Huxley (FH) equations. For an axon of diameter 10 μm, the minimal blocking frequency was changed from 6 to 3 kHz as the temperature was decreased from 37°C to 15°C. The maximal blocking temperature below which the axon could be blocked was increased from 22°C to 37°C as the stimulation frequency was increased from 4 to 8 kHz. The maximal blocking temperature was not influenced by axon diameter. Simulation analysis also revealed that activation of potassium channels might determine the temperature–frequency relationship. This study indicates that temperature might be one of the factors that cause the frequency discrepancy as reported in previous animal studies. Action Editor: Alain Destexhe     

A trade-off between the frequency and duration of bumblebee visits to flowers

Pollinator behavior influences plant reproduction in many ways. A traditional measure of pollination, the number of visits received, may be a poor predictor of plant reproductive success, particularly when there are trade-offs between visit quantity and components of visit quality. For example, the duration of pollinator visits may be negatively correlated with the number of visits received by a flower. We tested for a trade-off between the number of bumblebee visits and the duration of those visits in an experimental population of snapdragons (Antirrhinummajus: Scrophulariaceae). The duration of a bumblebee visit to a flower increased significantly with the time interval since the flower had last been visited. Over the lifetime of a flower the correlation between the total number and average duration of visits received by a flower was weakly negative. However, at the whole-plant level the correlation was positive: plants whose flowers received more visits also received visits of longer duration. Factors affecting the relationship between quantity and duration of pollinator visits to flowers also were investigated. Two factors weakened the negative dependence of average visit duration on number of visits received by individual snapdragon flowers: (1) the correlation between the total number of visits to a flower and the average interval between visits was only −0.53, as visits to individual flowers were not very evenly spaced over time, and (2) newly opened flowers received fewer and shorter visits than older flowers. Comparing whole plants, nectar production per flower varied dramatically across individuals, a probable explanation for the positive correlation between visit number and average duration per flower observed at the plant level. The potential for a trade-off between these two components of pollinator service exists when visit duration depends on reward quantity; whether the trade-off is realized will depend on variation in nectar production and on whether pollinators forage systematically. Received: 3 October 1997 / Accepted: 16 June 1998     

Relationship between the tension-time area and the frequency of stimulation in motor units of the rat medial gastrocnemius muscle.

The tension-time area is an estimation of the work performed by contracting motor units. The relationship between tension and frequency of stimulation and between tension-time area and frequency have been studied on 148 single motor units of the rat medial gastrocnemius muscle, under isometric conditions. Motor units were classified as fast fatigable (FF), fast resistant to fatigue (FR) or slow (S). Trains of stimuli of increasing frequency and constant duration were used. For all motor units a half of the maximum tetanic tension corresponded to lower frequencies compared to frequencies at a half of the maximum tension-time area. Moreover, the slopes of tension-frequency and area-frequency curves (change of tension or area per 1 Hz rise in frequency) were higher for slow than for fast motor units. The tension-time area per one pulse was calculated for different frequencies of stimulation. For slow units the maximum area per pulse corresponded to significantly lower frequencies than for fast ones, especially of FF type. However, for all three types of motor units this optimal frequency corresponded to sub-fused tetani with a tension of about 75% of the maximum tension, and with the fusion index slightly over 0.90. The absolute values of the maximum tension-time area per pulse revealed that in one contraction within the tetanus, slow units are generating greater work than FR units. The work performed by FF units is nearly two times larger than for S units, although the tension of slow units is over eight times lower. The presented results reveal that the contraction of slow motor units is much more effective than was suggested based on their low tension.     

Relationship between evaluation of the duration and loudness of short sounds]

The relation between loudness and duration judgments of short tones was investigated. Sounds (15 to 120 ms, 2500 Hz, about dB SPL), were exposed in pairs; one tone of the pair, the first or the second one, was twice as long as the other. Subjects had to compare the loudness of the tones, or the duration, or the loudness and the duration at the same time. Results show that the loudness judgments are independent of experiences with duration judgments and of immediate duration judgments, but duration judgments were less precise when loudness judged at the same time.     

Relation between the dynamics of a species-specific motor reaction and the duration of diencephalic stimulation

Species-specific reaction of thumping behaviour with the hind limbs in response to electrical stimulation of the ventromedial, dorsomedial and caudal parts of the hypothalamus was studied in chronic experiments on rabbits. Reaction of avoidance dominated during current action of various durations (1-20 s). The specific reaction under study appeared after the termination of stimulation and lasted for 30-120 s. The number of kicks in response to single stimulation depended on its duration (T). With T rising from 1 to 10 s, the number of kicks increased; with T being equal to 20 s, it decreased. The latency of the first kick after the termination of stimulation regularily increased with increase of its duration, and reaction intensity maxima shifted to the right along the axis of time. Possible mechanisms of limb kicking behaviour are discussed based on a transition of avoidance reaction during stimulus action to emotional reaction in post-stimulus period.     

Relationship between measures of balance and strength in middle-aged adults

The purpose of this study was to investigate the relationship between variables of static and dynamic postural control as well as between isometric and dynamic muscle strength. A single-group design was used. Thirty-two middle-aged healthy adults (mean age: 56 ± 4 years) performed measurements of static (unperturbed)/dynamic (perturbed) balance and of isometric (i.e., maximal isometric torque [MIT]; rate of torque development [RTD] of the plantar flexor)/dynamic (i.e., countermovement jump [CMJ] height and power) lower extremity muscle strength. No significant associations were observed between variables of static and dynamic postural control (r = +0.128-0.341, p > 0.05) and between measures of balance and strength (r = -0.189 to +0.316, p > 0.05). Significant positive correlations were detected between variables of isometric and dynamic strength ranging from r = +0.361 to +0.501 (p < 0.05). Further, simple regression analyses revealed that a 10% increase in the mean CMJ height (3.1 cm) was associated with 44.4 N·m and 118.4 N·m·s better MIT and RTD, respectively. The nonsignificant correlations between static and dynamic balance measures and between balance and strength variables imply that static and dynamic postural control and balance and strength are independent of each other and may have to be tested and trained complementarily.     

Relationship between eggshell strength and keratan sulfate of eggshell membranes

Eggshell strength is an important factor in an effort to minimize eggshell breakage, which is a significant problem in the egg production industry. In the current study, we isolated and quantified the specific glycosaminoglycans (GAGs) from the calcified eggshell and shell membranes, which are related to eggshell strength. Our data suggest that GAGs exist in calcified eggshell may influence morphology of shell but do not affect on increase of shell amount while GAGs of shell membranes are maybe highly associated with shell strength with an increase of shell weight. Shell strength showed a strong correlation with the content of GAGs (r=0.942, p<0.0005) and a weak relationship with uronic acid content (r=0.564, p=0.056) in shell membranes. Monosaccharides in shell membranes were determined by Bio-LC analysis for the identification of any specific GAGs related with shell strength. It indicates that the galactose content as a component of keratan sulfate (KS) has a significant correlation with eggshell strength (r=0.985, p<0.0005). These results suggest that eggshell strength is proportional to the KS content of eggshell membranes with an increase of eggshell weight.     

Photoinduced resonance phenomena in the human electroencephalogram as a function of frequency, intensity, and duration of stimulation

The features of resonance phenomena in high-resolution EEG structure were analyzed for two intensities and three values of duration of exposure to 20 constant frequencies of intermittent photic stimulation in a range of 1-20 Hz with 1 Hz steps. It was shown that with a 6 s step duration, an irregular activation of multiple spectral EEG components for both light intensities occurs. With longer durations (12 and 18 s) of fixed-frequency stimulation, the EEG reactions are of resonance nature. Low-intensity flashes cause only the resonance activation of the intrinsic oscillator in the range of dominant alpha-EEG frequency. During a more intensive stimulation, the resonance EEG phenomena are observed for the whole range of stimulation frequencies. The interval of 6-12 s is supposed to be the relaxation period for a system of brain electrical activity generation. After this time, the low-intensity stimuli cause the adaptation of the system to light, whereas more intensive flashes cause more pronounced resonance EEG phenomena and physiological effects.     

Relationship between the shape of equilibrium magnetic surfaces and the magnetic field strength

A local analysis of the magnetic field near an equilibrium magnetic surface shows that there is generally no relationship between the magnetic field strength and the shape of the surface. However, the relationship exists under additional requirements such as the absence of the toroidal current, symmetry conservation, and the conservation of the magnetic field strength distribution on the nearest surface. An equilibrium magnetic surface can be calculated by specifying three functions of two angular variables—the magnetic field strength, the periodic component of the magnetic potential, and the mean curvature of the surface.     

Control of glycogenolysis and hemodynamics in perfused rat liver by the sympathetic innervation. Dependence on stimulation frequency and duration

Perivascular stimulation of the hepatic nerves in the in situ perfused rat liver with a constant frequency of 20 Hz over a constant period of 5 min had previously been shown to cause an increase of glucose output, a shift from lactate uptake to release, a reduction in perfusion flow (Hartmann et al. (1982) Eur. J. Biochem. 123, 521-526) and an overflow of noradrenaline into the hepatic vein (Beckh et al. (1982) FEBS Lett. 149, 261-265). In the present study the dependence of the metabolic and hemodynamic effects on the frequency between 1 and 30 Hz and duration of stimulation between 0.5 and 5 min was investigated. Over a constant stimulation period of 5 min the alteration in glucose exchange was maximal with a frequency of 10 Hz and half-maximal with 4 Hz. The corresponding values for the exchange of lactate were 5 Hz and 2 Hz, respectively, and for the perfusion flow 2.5 Hz and 1.5 Hz, respectively. An increase of noradrenaline overflow was not observed with the lower frequencies of 1 and 2.5 Hz; it was maximal at 10 Hz and half-maximal at 6.5 Hz. At a constant frequency of 20 Hz the increase in glucose release was maximal with a total stimulation period of 1 min and half-maximal with a period of 0.4 min. An essentially maximal alteration of lactate exchange and perfusion flow as well as of noradrenaline overflow was also effected by a stimulation period of 1 min.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationship between the frequency of cultured oocytes fertilization and morphology of human sperm

The study has evaluated 304 cases under of vitro fertilization. Positive correlations were shown of semen parameters and fertilization rate. The individual spectrum of different sperm morphological types was shown to be constant. The discriminant analysis was used for comparison of two groups of patients--with low (less than 33%) and high (more than 67%) fertilization rates. The percentage of morphologically normal spermatozoa stronger correlated with fertilization rate. Although there was a fairly good correlation (in the order of their significance) with a progressive motility, grade of motility, percentage of slightly amorphous cells, sperm concentration, percentages of the neck and midpiece. The cut-off values of our discriminant test may conclusively predict the low (DF < 1.5) and the high (DF < 3.5) fertilization rates.     

Relationship between general motor activity of children at school and the duration of school tasks

A behavioural study was carried out with 20 children aged from 6 to 7 years attending the first year of primary school from 9:00 to 10:00 A.M. and 2:00 to 3:00 P.M. It appeared that the frequency and duration of getting up and moving around increased from the beginning to the end of both time intervals. There are significant positive correlations between these parameters and the duration of school tasks. It can be suggested that the general activity level is increased as a consequence of restraining children's general body activity and/or imposing on them sustained mental investment in school tasks.     

The duration and strength of postvaccinal measles immunity

A prolonged immunoepidemiological follow-up of a large group of children immunized against measles revealed a high epidemiological efficacy of a single vaccination. Cases of measles were registered only among those vaccinees in whose blood sera no specific hemagglutinins were detectable by titration with 4 hemagglutinating units of measles antigen prior to the disease. The study showed that groups of children seronegative with respect to measles appeared, as a rule, after unsatisfactory immunization and not due to loss of postvaccinal immunity with time. Properly immunized children in whom the formation of antimeasles antibodies had occurred in response to the injection of live measles vaccine retained postvaccinal immunity for more that 15 years (the term of observation).