Relation between vibratory sensibility and electric signal of living body

The paper presents psychological experiments carried out using a vibrometer as an acoustical calibration apparatus for triangular, sawtooth, square and pulse waves. The study has shown the relationship between the vibratory sensibility and the electric signal generated in a living body. The threshold curve for square waves is lower by 12·3dB than that for sine waves at about 30 Hz. We consider that the evaluation of vibratory sensibility should be performed by a physical measurement, which also relates to subjective evaluation It is necessary to find the new physical measurement. We have observed that subjective vibratory sensibility and potential variations take place linearly with the vibratory level.     

Estimation of the distribution of intramuscular current during electrical stimulation of the quadriceps muscle

Electrical stimulation is commonly used for strengthening muscle but little evidence exists as to the optimal electrode size, waveform, or frequency to apply. Three male and three female subjects (22–40 years old) were examined during electrical stimulation of the quadriceps muscle. Two self adhesive electrode sizes were examined, 2 cm × 2 cm and 2 cm × 4 cm. Electrical stimulation was applied with square and sine waveforms, currents of 5, 10 and 15 mA, and pulse widths of 100–500 μs above the quadriceps muscle. Frequencies of stimulation were 20, 30, and 50 Hz. Current on the skin above the quadriceps muscle was measured with surface electrodes at five positions and at three positions with needle electrodes in the same muscle. Altering pulse width in the range of 100–500 μs, the frequency over a range of 20–50 Hz, or current from 5 to 15 mA had no effect on current dispersion either in the skin or within muscle. In contrast, the distance separating the electrodes caused large changes in current dispersion on the skin or into muscle. The most significant finding in the present investigation was that, while on the surface of the skin current dispersion was not different between sine and square wave stimulation, significantly more current was transferred deep in the muscle with sine versus square wave stimulation. The use of sine wave stimulation with electrode separation distances of less then 15 cm is recommended for electrical stimulation with a sine wave to achieve deep muscle stimulation.     

Frequency dependence of the cardiac threshold to alternating current between 10 Hz and 160 Hz

It is still unclear what fundamental criteria influence the ability of alternating current (AC) to induce ventricular fibrillation (VF) in vivo. As the VF threshold has a bowl-shaped relationship with frequency (showing a minimum threshold at some frequency), similar to the nervous system, one proposed model has assumed that the mechanisms underlying AC stimulation of nerves are at work for VF induction. More recent work has suggested a second approach, whereby a simple RC-like model is sufficient to understand the cardiac AC stimulation threshold's frequency dependence, suggesting that some unarticulated mechanism is at work for VF. The paper directly tests these two models. In 12 intact dogs and 20 intact guinea pigs, DC pulses were used to stimulate AC square and AC sine waves at 10, 20, 40, 80 and 160 Hz. All electrodes were endocardial, with the return electrode being on a paw or thorax. It was found that, for square and sine wave stimulation in both dogs and guinea pigs, the stimulation threshold increased monotonically with frequency from 10 Hz up to 160 Hz (p<0.01 for dogs and guinea pigs). Between 80 and 160 Hz, the AC stimulation threshold doubled, exactly as predicted by an RC model. It was concluded that the AC stimulation threshold is not bowl-shaped and is best understood with an RC model. As the VF threshold does exhibit a bowl-shape with frequency, as opposed to the stimulation threshold which does not, the VF induction frequency dependence must have different origins.     

Ontogenesis of electroencephalographic seizure patterns in developing chick embryos during recovery from hypothermic hypoxia

Chick embryos between the 15th and 20th day of incubation were subjected to hypothermia of 20°C followed by nitrogenous hypoxia until the cerebral EEG showed no fluctuations of potential. The embryos were exposed to air 15 or 30 min later. Body temperature was raised to 30°C and maintained there for 1 hr before being raised to 36°C, during which time 2 types of seizure episodes of rhythmic waves appeared. Type I was characterized by an ontogenetically later appearance (after the 15th day), larger amplitude, spike and slow wave patterns, a frequency of .3-3.5 Hz with the slowest in the younger embryos, and a duration of 1 to several minutes. Type II was characterized by an earlier ontogenetic appearance, small amplitude, a frequency of 1-30 Hz, and a duration of a few seconds to several minutes. None of these seizure episodes was observed after body temperature had reached 36°C. About the 17th day of incubation, the physiological components responsible for producing EEG patterns during episodes seem to undergo an abrupt maturational change indicated by the increase in percentage of embryos undergoing Type I episodes, and by changes in frequency of waves and duration of episodes.     

Time-based prediction in motor control: evidence from grip force response to external load perturbations

An object held in precision grip creates predictable load forces on the hand during voluntary hand movement and these are associated with anticipatory modulation of grip force. Conflicting results have been obtained over whether predictable external load perturbations result in anticipatory grip force responses (e.g. Blakemore et al. in J Neurosci 18(18):7511–7518, 1998; Weeks et al. in Exp Brain Res 132:404–410, 2000). This paper investigated whether the discrepancies reflect differences in the methods used in estimating the time delay. Subjects held a manipulandum that delivered load force perturbations in the form of pulses of variable duration and interval or periodic 0.5 and 1 Hz square waves or sinusoids. The grip forces exerted by the subjects were measured. Two methods were used to assess the time delay of the grip force in relation to the load force: (1) cross-spectral analysis, (2) a single threshold method applied on time-locked averaged data. Despite a phase lag shown by the cross-spectral analysis, the threshold method revealed grip force increased 264.8±40.2 ms before the onset of the load force when 0.5 Hz square waves were used as the load force perturbation and 70.2±17.0 ms before the load force when 1 Hz square waves were used. Computer simulations indicated that the single threshold method gives a more sensitive estimate of the onset time than the cross-spectral analysis. We conclude that discrepancies in previous studies reflect differences in the methods used to assess the time-delay and that there is an anticipatory component in the grip force response to predictable external load perturbation.     

Dependence of stretch reflexes on amplitude and bandwidth of stretch in human wrist muscle

The tonic stretch reflex was investigated using small-amplitude displacements (<4.2°) of the wrist while subjects maintained average contraction levels of 25% of maximum in flexor carpi radialis. The wrist displacements were designed to preclude voluntary following but at the same time were confined to the frequency range most relevant to voluntary movements. They included a broad-frequency band (0–12 Hz) signal as well as sets of narrow-band signals spanning the range from 0 to 10 Hz. The maximum frequency was set so as to remain within the linear encoding bandwidth of the reflex system and thereby minimize distortion. The effects of frequency bandwidth and amplitude of the displacement perturbations were tested in separate experiments. The coherence square, gain and phase between the EMG and angular displacement were calculated in order to characterize the stretch reflex under these conditions. It was found that the phase of the reflex response was dependent on both bandwidth and amplitude. For narrow-band displacements, the phase advance was about 30° greater over the frequency range tested than for broad-band displacements, suggesting that the reflex response may be influenced by the predictability of the perturbation. At the smallest amplitude of 0.3°, the peak phase advance was about 20° greater than at the largest amplitude of 4.2°. The gain was also higher and rose more steeply with frequency at smaller amplitudes. In the frequency range up to 12 Hz, the tonic stretch reflex responds most effectively to smaller-amplitude, more regular, higher-frequency inputs and this is consistent with a role for the reflex in counteracting small-amplitude oscillations, tremors and errors of voluntary movement. Received: 19 October 1998 / Accepted: 23 May 1999     

Paramphistomum daubneyi and Fasciola hepatica: influence of temperature changes on the shedding of cercariae from dually infected Lymnaea truncatula

Dual infections of Lymnaea truncatula with Paramphistomum daubneyi and Fasciola hepatica were performed to determine whether temperature changes in snails (daily water change with spring water at 6°–8 °C, which subsequently increased to room temperature at 20 °C) would influence snail infection and the production of cercariae by both trematodes. At day 30 postexposure the surviving snails were individually placed in petri dishes to constitute two groups. Snails from the first group were maintained at a temperature of 20 °C, and the water in the petri dishes was changed daily. The protocol was identical for the second group of snails except that the water temperature was 6°–8 °C when changed. The interval between exposure and the first shedding of cercariae in snails immersed in cold water for a short period was longer (67–69 days instead of 48–50 days in the 20 °C group). In both groups, snails infected only with F. hepatica or P. daubneyi or with both trematodes were detected. In snails infected only with F. hepatica the frequency of cercaria-shedding snails and the total number of metacercariae were significantly greater in the 20 °C group. Inversely, in snails infected only with P. daubneyi the frequency of cercaria-shedding snails and the number of metacercariae were significantly greater in the 6°–8 °C group. In snails harboring both trematode larval forms, no significant difference in the frequencies of cercaria-shedding snails between the two groups was noted. Metacercariae of both trematodes were obtained from these snails. In the 20 °C group, F. hepatica metacercariae were more numerous, whereas in the 6°–8 °C group the number of P. daubneyi metacercariae was greater. From these results it appears that greater activity of P. daubneyi cercariae occurs in snails subjected to daily temperature changes (from 6° to 20 °C). Received: 24 March 1999 / Accepted: 1 April 1999     

The dynamics of vertical vergence

 We measured the gain and phase of vertical vergence in response to disjunctive vertical oscillations of dichoptic textured displays. The texture elements were m-scaled to equate visibility over the area of the display and were aperiodic and varied in shape so as to avoid spurious binocular matches. The display subtended 65° and oscillated through peak-to-peak amplitudes from 18 arc min to 4° at frequencies from 0.05 to 2 Hz – larger ranges than used in previous investigations. The gain of vergence was near 1 when the stimulus oscillated at 18 arc min at a frequency of 0.1 Hz or less. As the amplitude of stimulus oscillation increased from 18 arc min to 4°, vergence gain decreased at all frequencies, which is evidence of a nonlinearity. Gain declined with increasing stimulus frequency but was still about 0.5 at 2 Hz for an amplitude of 18 arc min. Phase lag increased from less than 10° at a stimulus frequency of 0.05 Hz to between 100° and 145° at 2 Hz. Overall, the dynamics of vertical vergence resemble the dynamics of horizontal vergence and cyclovergence. Received: 11 September 1996 / Accepted: 28 January 1997     

Development of a non-invasive treatment system for urinary incontinence using a functional continuous magnetic stimulator (FCMS)

A system composed of a functional continuous magnetic stimulator (FCMS) and a saddle-type coil has been developed for non-invasive treatment of urinary incontinence, especially stress incontinence and urge incontinence. The FCMS conditions were as follows: 2 kW maximum electrical power consumption, 800 V maximum capacitor voltage, 720 μs pulsewidth (180 μs rise time), and 5–30 Hz frequency. A frequency between 5 and 10 Hz is used to treat urge incontinence and a frequency between 25 Hz and 30 Hz is used to treat urge incontinence. The coil (120 mm long, 90 mm wide and 50 mm thick) fits the most suitable region for this treatment, the region from the anus to the perineum. The coil is cooled to maintain a coil temperature between 20 and 25°C so that it can be used efficiently and safely. In experiments with anaesthetised dogs, it was confirmed that the urethral pressure increased when the circumference of the perineum received continuous magnetic stimulation of 720 μs pulsewidth (180 μs rise time), 10Hz frequency and about 520 V capacitor voltage. This result suggests that magnetic stimulation can be effective as a urinary incontinence therapy.     

Spectral analysis of heart rate fluctuations and optimum thermal management for low birth weight infants

Spectral analysis of heart rate variability is studied in 10 healthy growing premature infants to investigate the changes in autonomic balance achieved as a function of changes in skin temperature. Heart rate is obtained from ECG recordings and the power spectrum of beat-to-beat heart rate fluctuations is computed. The infants maintain mean rectal temperature within 36.3–37.2°C, while skin temperature changes. The respiratory rate does not change at the different servocontrol set points. Heart rate is found to increase slightly, but consistently. The low-frequency band (0.02–0.2 Hz), reflecting the interplay of the sympathetic and parasympathetic tone and known to be maximum at the thermoneutral zone, is maximum at 35.5 and 36°C and decreases gradually to a lower level at a servocontrol temperature of 36.5–37°C. The high-frequency band (0.2–2.0 Hz), coinciding with the respiratory peak and reflecting parasympathetic activity, is significantly elevated at 36°C (p<0.01). The minimum low: high ratio, indicating the minimum sympathetic-parasympathetic balance and possibly reflecting the most comfortable conditions, occurs at 36°C, although the differences are not statistically significant. Servocontrol skin temperature may thus be adapted, and possibly selected at 36°C for growing premature infants in an attempt to achieve thermal comfort and more balanced autonomic activity.     

Thermal Regulation of Spontaneous Spike Frequency and Concomitant Changes in the Amplitude of Spikes from Cortical Neurons

Studies using living slices of guinea pig sensorimotor cortex showed that changes in temperature from 24°C to 37°C produced stepwise increases in neuron spike frequency at two temperature zones: 27–29°C and 34–36°C. Changes in spontaneous activity were accompanied by decreases in spike amplitude at t < 27°C and t > 34°C. After cooling to 24°C, spike amplitude generally recovered completely when the temperature was increased to 32–34°C. The decrease in spike amplitude at t > 35°C could not be restored by decreasing the temperature. It is suggested that these effects are associated with the K⁺ permeability of neuron membranes.     

Comparative Nuclear Magnetic Resonance Studies of Diffusional Water Permeability of Red Blood Cells from Different Species. XII. Dog (<Emphasis Type="BoldItalic">Canis familiaris</Emphasis>) and Cat (<Emphasis Type="BoldItalic">Felis domestica</Emphasis>)

The diffusional water permeability (P _d ) of dog and cat red blood cell (RBC) membrane has been monitored by a doping nuclear magnetic resonance (NMR) technique on control cells and following inhibition with p-chloromercuribenzene sulphonate (PCMBS). The values of P _d were in the case of cat RBC ∼3.0 × 10⁻³ cm/s at 15 °C, 3.5 × 10⁻³ cm/s at 20 °C, 4.2 × 10⁻³ cm/s at 25 °C, 4.4 × 10⁻³ cm/s at 30 °C and 5.9 × 10⁻³ cm/s at 38 °C. In case of dog RBC the values of P _d were higher ∼3.8 × 10⁻³ cm/s at 15 °C, 4.6 × 10⁻³ cm/s at 20 °C, 5.0 × 10⁻³ cm/s at 25 °C, 5.9 × 10⁻³ cm/s at 30 °C and 7.9 × 10⁻³ cm/s at 37 °C. Systematic studies of the effect of PCMBS on water diffusion indicated that in the case of dog RBCs the maximal inhibition was reached in 15–30 min with 1 mm PCMBS, whereas in the case of cat RBCs in 60 min with 1 mm PCMBS or in 30 min with 2 mm PCMBS. The values of maximal inhibition in the case of cat RBC were in the range of 55–60% at 15 °C, 60–68% at 20 °C and 25 °C, 50–60% at 30 °C and 50–55% at 37 °C. In the case of dog RBC the corresponding values were higher, 75–80% at 15 °C, 70–80% at 20 °C and 25 °C, 65–70% at 30 °C and 55–60% at 37 °C. The basal permeability to water was estimated to be ∼1 × 10⁻³ cm/s −2 × 10⁻³ cm/s in the range of temperatures of 25–37 °C. The activation energy of water diffusion E _a,d was ∼19 kJ/mol for the dog RBC and ∼23 kJ/mol for the cat RBC. After incubation with PCMBS the values of E _a,d increased, reaching 40 kJ/mol in conditions of maximal inhibition of water exchange. The membrane polypeptide electrophoretic pattern of dog and cat RBCs has been compared with its human counterpart. Dog and cat RBCs contained higher amounts of spectrin (band 1 and 2) and lower amounts of bands 4.4, 4.2, band 5 and band 7 compared to human RBCs. Band 4.9 was decreased only in the cat RBCs, whereas band 6 was decreased only in the dog RBCs. Correspondence and offprint requests to: Gheorghe Benga, Department of Cell and Molecular Biology, ‘Iuliu Haţieganu’ University of Medicine and Pharmacy, 6 Pasteur St, 3400 Cluj-Napoca, Romania. Tel:/Fax: 40–64–194373; e-mail: GBenga@personal.ro; gbenga@umfcluj.ro     

Discharge of pursuit-related neurons in the caudal part of the frontal eye fields in juvenile monkeys with up–down pursuit asymmetry

The smooth-pursuit system uses retinal image-slip-velocity information of target motion to match eye velocity to actual target velocity. The caudal part of the frontal eye fields (FEF) contains neurons whose activity is related to direction and velocity of smooth-pursuit eye movements (pursuit neurons), and these neurons are thought to issue a pursuit command. During normal pursuit in well-trained adult monkeys, a pursuit command is usually not differentiable from the actual eye velocity. We examined whether FEF pursuit neurons signaled the actual eye velocity during pursuit in juvenile monkeys that exhibited intrinsic differences between upward and downward pursuit capabilities. Two, head-stabilized Japanese monkeys of 4 years of age were tested for sinusoidal vertical pursuit of target motion at 0.2–1.2 Hz (±10°, peak target velocity 12.5–75.0°/s). Gains of downward pursuit were 0.8–0.9 at 0.2–1.0 Hz, and peak downward eye velocity increased up to ~60°/s linearly with target velocity, whereas peak upward eye velocity saturated at 15–20°/s. The majority of downward FEF pursuit neurons increased the amplitude of their discharge modulation almost linearly up to 1.2 Hz. The majority of upward FEF pursuit neurons also increased amplitude of modulation nearly linearly as target frequency increased, and the regression slope was similar to that of downward pursuit neurons despite the fact that upward peak eye velocity saturated at ~0.5 Hz. These results indicate that the responses of the majority of upward FEF pursuit neurons did not signal the actual eye velocity during pursuit. We suggest that their activity reflected primarily the required eye velocity.     

Effect of atropine,propranolol, and atenolol on wave structure of heart rate oscillations in rats

Were studied the effects of atropine and β-adrenoblockers on the power of very low (<0.25 Hz), low (0.25–0.70 Hz), and high frequency (0.7–1.8 Hz) waves of the heart rhythm in wakeful rats. Atropine reduced the power of all waves in 100% cases. Propranolol on average decreased the power of very low frequency waves and increased the power of low and high frequency waves, although opposite effects were observed in many cases. Atenolol produced similar effects. Some animals demonstrated spontaneous moderation of respiratory rate to a level corresponding to low-frequency oscillations of the heart rhythm accompanied by elevation of the relative power of low frequency waves. Inconsistency of the effects of β-adrenoblockers in rats can be related to variability of sympathetic tone and spontaneous deceleration of respiration with the corresponding changes of low frequency waves. Augmentation of the high frequency waves during application of β-adrenoblockers is not related to their action on CNS. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 145, No. 4, pp. 364–367, April, 2008     

Magnetophosphenes: a quantitative analysis of thresholds

Low-frequency and transient magnetic fields of moderate flux densities are known to generate visual phenomena, so-called magnetophosphenes. In the present study, time-variable very low frequency (10–50 Hz) electromagnetic fields of moderate flux density (0–40 mT) were used to induce magnetophosphenes. The threshold values for these phosphenes were determined as a function of the frequency of the magnetic field both in normal subjects and colour defective ones. Maximum sensitivity occurred at a frequency of approximately 20–30 Hz, and with broad-spectrum light the threshold flux density was 10–12 mT. The threshola values were found to be dependent upon the intensity and the spectral distribution of the background light. Sensitivity decreased during dark adaptation. In certain respects deutans differed from subjects with normal colour vision. Possible mechanisms for generation of magnetophosphenes are discussed. The present magnetic threshold curves show a close resemblance to corresponding curves obtained by electric stimulation at various frequencies provided the electric thresholds are divided by the a.c. frequency. These problems are under current investigation in our laboratory. This is in full agreement with the assumption that the fluctuating magnetic field affects retinal neurons by inducing currents which polarise synaptic terminals.     

Facilitation of the withdrawal reflex by repeated transcutaneous electrical stimulation: an experimental study on central integration in humans

In the present human study, we aimed to investigate the facilitation of both the subjective pain responses, and the withdrawal reflex to consecutive transcutaneous electrical stimuli as measures of temporal summation. The frequency (0.5–20 Hz) and intensity (0.4–0.8 times the reflex threshold,  ×RT) of the electrical stimuli were systematically varied. When using repeated stimulation, the stimulus intensity that evoked pain was lower than that required by a single stimulus (temporal summation). Temporal summation leading to pain was found to depend significantly upon both frequency and intensity (e.g. stimulation at 1 Hz caused summation at 0.8 × RT, whereas stimulation at 20 Hz caused summation at 0.6 × RT). The strongest reflex facilitation, and hence the strongest pain intensity was obtained for stimulation at 10–20 Hz at an intensity of 0.8 × RT. In conclusion, the results of the present human study demonstrate clearly that a stimulus that is perceived as a localised, repetitive tactile tap can be integrated and cause severe pain. This suggests that pathologically generated sparse nociceptive afferent activity causes strong pain by central integration. This might be one mechanism to explain why clinical conditions can become excruciatingly painful despite the fact that the pathophysiological changes seem to be marginal (e.g. minor nerve trauma). Received: 26 April 1999 / Accepted: 12 August 1999     

Magneto- and electrophosphenes: A comparative study

The purpose of this study was to compare the threshold values for magnetophosphenes and electrophosphenes under identical experimental conditions. Such comparisons between the phosphene types would increase our knowledge of the mechanism of the interaction between magnetic fields and electric current, respectively, and excitable tissue. The phosphenes were generated in the frequency range 10–45 Hz at moderate magnetic flux densities [up to 40 mT (400 G)] and electric currents up to 0.3 mA, respectively. The first part of the study was devoted to the problem of how electrode location and consequent current directions influence the threshold values of electrophosphenes. In the second part a comparison was made of the threshold values for electrophosphenes and magnetophosphenes under identical experimental conditions apart from the stimulation method. With electric-current stimulation in different directions no great differences were obtained with regard to the mean value for the threshold values within the frequency range 10–30 Hz. However, from 30 Hz upwards a significant difference developed between the threshold values for some of the curves. When generating electrophosphenes and magnetophosphenes we found significant differences in the threshold values between approximately 25 and 45 Hz. Both types of phosphenes had a concurring sensitivity maximum at 20 Hz. The deviations between the curves may be due, among other factors, to the generation of different current paths in electrical and magnetic stimulation, respectively.     

Analysis of the dielectric properties of keratin in the α-dispersion electric field region

The dielectric method has been applied to study the relaxation mechanisms of non-irradiated and γ-irradiated keratin-water systems in the electric field frequency range of 10¹–10⁵ Hz and at temperatures from 22 to 190°C. Measurements were performed for keratin samples containing 3% water by mass at room temperature. The doses of γ-irradiation were 5, 50 and 200 kGy. The influence of water and γ-irradiation on the dielectric behaviour of keratin was negligible up to 120°C but significant in the temperature range of 140–190°C. In the first temperature range, the motion of polar side chains was characterised by a low activation energy of 11 kJ mol⁻¹, while longer relaxation times varied from 418 to 155 ms. In the range 140–190°C, the release of the strongly bound water in keratin samples irradiated with doses of 0–50 kGy was evidenced by the high value of the activation energy of 84 kJ mol⁻¹ and shorter relaxation times varying from 43 to 3 ms. The value of the activation energy decreased to 55 kJ mol⁻¹ for keratin samples irradiated with 200 kGy as a result of degradation of the hydrogen bond between the water and polar groups of the main chain of the macromolecule. The results presented may be useful in bio-electrical impedance analysis, for physiological and clinical research. The method applied in vivo should permit detection of changes in the stratum corneum induced by water, ionising radiation, cosmetics and diseases such as fibromyalagia or diabetic foot ulcers.     

Artifactual changes in the haematocrit buffy coat of stored anti-coagulated blood samples of farm animals

The buffy coat percentage (BCP) of centrifuged anti-coagulated blood is routinely clinically used to estimate the total leukocyte count (TLC). There had been observations in our clinical laboratory of BCPs that do not correlate with TLC, especially in blood samples in which centrifugation were delayed. This study therefore investigated the artifactual changes that occur in the BCP of stored anti-coagulated blood samples of farm animals. The BCPs of blood samples from a total of 16 cattle, 18 goats, 15 pigs, and 16 chickens were determined immediately upon blood collection to obtain the baseline value (BV). The blood samples were then divided into three parts and stored at 5°C (3–7°C), 30°C (27.5–32.5°C), and 37°C (35.5–38.5°C). Further BCP determinations on the samples were carried out at 24-h intervals for 72 h (3 days). Results showed that there were statistically significant increases (p < 0.05) in BCP of cattle blood samples at all temperatures of storage as from the 48th hour of storage onwards, in goat blood samples stored at 5°C and 37°C at the 72nd hour of storage and as from the 48th hour of storage in the goat blood samples stored at 30°C, in pig blood samples as from the 24th hour of storage onwards for all the storage temperatures, and in chicken blood samples stored at 30°C and 37°C as from the 48th hour of storage onwards. However, clinically significant increases (BCP > 1.5%) occurred only in cattle and chicken blood samples stored at 30°C and 37°C at hour 72 of storage and in pig blood samples stored at 30°C and 37°C as from the 48th hour of storage onwards. It was concluded that statistically significant increases in BCP occur in the blood of cattle, goats, pigs, and chicken during storage, but clinically significant increases that could lead to a false notion of leukocytosis do occur in the BCP of stored anti-coagulated blood of cattle, pigs, and chicken when the blood is stored/kept at 30°C and 37°C.     

Cross-bridge kinetics of fast and slow fibres of cat jaw and limb muscles: correlations with myosin subunit composition

Mechanical properties of the jaw-closing muscles of the cat are poorly understood. These muscles are known to differ in myosin and fibre type compositions from limb muscles. This work aims to correlate mechanical properties of single fibres in cat jaw and limb muscles with their myosin subunit compositions. The stiffness minimum frequency, f_min, which reflects isometric cross-bridge kinetics, was measured in Ca²⁺-activated glycerinated fast and slow fibres from cat jaw and limb muscles for temperatures ranging between 15 and 30°C by mechanical perturbation analysis. At 15°C, f_min was 0.5 Hz for limb-slow fibres, 4–6 Hz for jaw-slow fibres, and 10–13 Hz for limb-fast and jaw-fast fibres. The activation energy for f_min obtained from the slope of the Arrhenius plot for limb-slow fibres was 30–40% higher than values for the other three types of fibres. SDS-PAGE and western blotting using highly specific antibodies verified that limb-fast fibres contained IIA or IIX myosin heavy chain (MyHC). Jaw-fast fibres expressed masticatory MyHC while both jaw-fast and jaw-slow fibres expressed masticatory myosin light chains (MLCs). The nucleotide sequences of the 3′ ends of the slow MyHC cDNAs isolated from cat masseter and soleus cDNA libraries showed identical coding and 3′-untranslated regions, suggesting that jaw-slow and limb-slow fibres express the same slow MyHC gene. We conclude that the isometric cross-bridge cycling kinetics of jaw-fast and limb-fast fibres detected by f_min are indistinguishable in spite of differences in MyHC and light chain compositions. However, jaw-slow fibres, in which the same slow MyHCs are found in combination with MLCs of the jaw type, show enhanced cross-bridge cycling kinetics and reduced activation energy for cross-bridge detachment.