Spectral analysis on fluctuation of heat period in paralyzed,vagotomized, and unanesthetized decerebrate cats

Spectral analysis was performed on the heart period fluctuation in vagotomized, paralyzed, and unanesthetized decerebrate cats. The heart period was measured as the time interval between successive R waves of the electrocardiograms. When end-tidal P_CO2 was set at the same level as that before immobilization, the power spectral density plot of the heart period fluctuation showed several distinct peaks: one peak corresponded to the frequency of the artificial ventilator and the others to its harmonics. In addition, the spectral density plot had another peak centered at the intrinsic respiratory frequency evaluated by recording efferent phrenic neural discharges. The amplitude of these spectral peaks tended to become greater when the end-tidal P_CO2was increased by adding CO₂ to the input gas. Our results, therefore, provide evidence that the heart period is modulated not only by the artificial ventilation rhythm but also by the centrally generated respiratory rhythm, and suggested that the strength of such central interactions between cardiac and respiratory rhythms varies depending on the end-tidal P_CO2 level.     

Spectral analysis of the cardiac rhythm of fishes

Spectral analysis of the rhythmograms in the cod Gadus morhua callarias, plaice Pleuronectes platessa, herring Clupea harengus membras and trout Salmo gairdneri revealed complex wave structure of their cardiac rhythm. In all the species investigated, slow (0.01-0.06 Hz), intermediate (0.06-0.25 Hz) and fast (0.25-0.5 Hz) waves were recorded. It is suggested that the wave structure of cardiac rhythm reflects rather complicated relationships between functional systems regulating cardiac activity.     

Spectral analysis of respiratory parameters in defensive respiratory reflexes

A detailed analysis of respiratory signals in normal breathing and defensive respiratory reflexes was performed to obtain maximum information that can be used for modelling of respiratory processes. Physiological interpretation of the problem is difficult and requires further measurements to achieve convincing conclusions. We suggest therefore that the search for appropriate methodological backgrounds should contribute to further clarification of the problems concerned with reciprocal linkage of the respiratory signals. Appropriate attention must be paid to investigations aimed at explaining the regulatory mechanisms of breathing.     

昼夜节律对呼吸功能的影响

昼夜节律是生物以24小时左右为基本时间单位而发生的生理、行为的周期变化。人类血压、体温、激素分泌等都存在昼夜节律,调节人类的基本活动。研究发现,人类的呼吸功能存在日间和夜间的差异。那么,呼吸是否也存在昼夜节律?呼吸的昼夜节律是否受睡眠、觉醒状态的影响?本文对上述问题进行初步阐述。     

Medullary raphe neuron activity is altered during fictive cough in the decerebrate cat.

Chemical lesions in the medullary raphe nuclei region influence cough. This study examined whether firing patterns of caudal medullary midline neurons were altered during cough. Extracellular neuron activity was recorded with microelectrode arrays in decerebrated, neuromuscular-blocked, ventilated cats. Cough-like motor patterns (fictive cough) in phrenic and lumbar nerves were elicited by mechanical stimulation of the intrathoracic trachea. Discharge patterns of respiratory and nonrespiratory-modulated neurons were altered during cough cycles (58/133); 45 increased and 13 decreased activity. Fourteen cells changed firing rate during the inspiratory and/or expiratory phases of cough. Altered patterns in 43 cells were associated with the duration of, or extended beyond, the cough episodes. The different response categories suggest that multiple factors influence the discharge patterns during coughing: e.g., respiratory-modulated and tonic inputs and intrinsic connections. These results suggest involvement of midline neurons (i.e., raphe nuclei) in the cough reflex.     

The effect of intraspinal microinjection of dopamine on the C-fiber reflex in the acute decerebrate spinal cat.

Dopamine microinjection (10 μg) into the ventral spinal cord gray matter of the L₇ segment of the spinal cord facilitated the C-fiber reflex; however, facilitation occurred after a latency of 15 min. In contrast norepinephrine (10 μg) microinjections facilitated the C-fiber reflex after a shorter latency (2 min). Treatment of the cat with a dopamine ß-hydroxylase inhibitor prevented the facilitatory effect of dopamine. These observations indicate that microinjected dopamine facilitates C-fiber reflexes by serving as a precursor for norepinephrine.     

Unraveling the mechanism for respiratory rhythm generation

Breathing is generated by a neuronal network located within the caudal brainstem. One area of particular significance for respiratory rhythm generation is the pre-B?tzinger (preBotC) complex in the ventrolateral medulla. An important step towards understanding the cellular and network basis by which neurons within this region generate the respiratory rhythm was made in a recent study by Koshiya and Smith.(1) Using simultaneous image analysis and electrophysiological techniques these authors identified a discrete population of synaptically-coupled pacemaker neurons within the preBotC. They postulated that these neurons constitute the minimal essential network component (kernel) for generating the respiratory rhythm. BioEssays 22:6-9, 2000.     

Slow respiratory stimulant effect of hyperoxia in chemodenervated decerebrate cats.

A direct stimulating action of oxygen on the CO2 respiratory control system was determined from steady-state and dynamic observations in unanesthetized decerebrate cats. In peripheral nerve-intact animals, inhalation of oxygen (1 atm) produced a small but significant shift to the left as well as a decrease in slope in the steady-state VT vs. log PACO2 relationship. Carotid sinus neurotomy more than doubled the shift, to the extent that the mean PACO2 apneic point was lowered by 6.5 mmHg. Neither vagotomy nor chronic ablation of the area postrema had any detectable influence on the stimulating effect of oxygen on CO2 responsiveness. The arterial-alveolar PCO2 difference, prior to and following carotid chemo-denervation, remained unchanged or was increased by a negligible amount during oxygen inhalation. The oxygen threshold for respiratory stimulation, obtained isocapnically, occurred between 115 and 200 mmHg; VT then increased exponentially tending to level off as PAO2 approached 1 atm. The dynamic response to sudden presentation of oxygen after carotid chemodenervation consisted of a monotonic rise in VT, starting after 20-30 s with a t 1/2 of about 75 s.     

The effect of weak variable extremely low frequency magnetic fields on the infra-day rhythm of the rat sympathoadrenal system]

It was found in open test that changing magnetic fields with 8 Hz frequency and 5 mcTl induction in daily 3 hours exposition on rats with a middle level of the mobile activity move the phase of diuresis daily rhythms and epinephrine and norepinephrine yield as well. In rats with desinchronosis provoked by hypokinesia the changing magnetic fields restore the synchronism of the studied processes.     

Fictive respiratory rhythm in the isolated brainstem of frogs

Spontaneous rhythmically bursting activity was recorded from the trigeminal, vagal and hypoglossal nerve roots of the isolated brainstem from the frogsRana catesbeiana andRana pipiens superfused with a bicarbonate-free HEPES-buffer solution. Burst frequency, burst duration and the activity profile of the spontaneous neural discharges in vitro resembled those of a less radical preparation, the decerebrate, fictively breathing frog. After complete midsagittal section, each half of the isolated brainstem generated its own rhythmic neural activity which resembled that of the intact isolated brainstem. The spontaneous activity generated within each half of the brainstem is probably coordinated by decussating axons or by groups of neurons located along the midline of the brainstem. Our results suggest that these coordinating entities extend the length of the brainstem (in a rostro-caudal dimension) and the degree of contact rather than the location of the contact between the two halves of the brainstem determines the synchronization of the right and left halves. Burst frequency of both the intact and hemisected brainstem preparation was decreased by alkaline challenge and increased by acid challenge. We conclude that this endogeneous rhythmic activity represents the efferent motor output underlying lung ventilation in these animals.Abbreviations EMG electromyogram - ENG electroneurogram - V trigeminal nerve - Vmd mandibular branch of trigeminal nerve - X vagal nerve - X1 laryngeal branch of vagal nerve - H hypoglossal nerve - Hsh sternohyoid branch of hypoglossal nerve - Hm main branch of hypoglossal nerve     

Correlation between the kinematics of hindlimb movement and efferent activity in the decerebrate cat during scratching

The statistical relationship was investigated between temporal and amplitude parameters of scratching motion performed by the hindlimb and those of muscular activity during naturally-occurring scratching in the course of experiments on decerebrate cats. The factors mainly determining movement parameters, such as amplitude or the speed and duration of a specific phase were found to be the intensity of EMG activity displayed by scratching and aiming muscles and the duration of aiming muscle activity. Findings from experiments involving limb deafferentation showed that the statistical relationship between the parameters of motion and muscular electrical activity reflect certain patterns of scratch generator operation. Certain relationships linking parameters of electrical activity changed due to the effects of afferent signals.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 525–533, July–August.     

Impact of meal timing and frequency on the twenty-four-hour leptin rhythm

OBJECTIVE: To study the influence of changes in meal timing and frequency on the diurnal rhythm of leptin and on the 24-hour profile of insulin and glucose. PATIENTS AND METHODS: Five obese women were studied twice during a weight-maintaining diet in either 3 daily or 8 day and night equal portions. Blood was sampled for 24-hour profiles of leptin and insulin. RESULTS: During the 8-meal intervention, the 24-hour rhythm of leptin changed significantly: the amplitude decreased (p = 0.0089) and the acrophase was delayed by 168 min (p = 0.021). Also, 8 small insulin secretion peaks occurred instead of the 3 postprandial high insulin peaks. CONCLUSION: The dispersion of food intake over 24 h affects the diurnal leptin rhythm. These changes could not be attributed to changes in circadian timing or energy balance. Instead, changes in daily insulin secretion profiles might play a role.     

Responses of nucleus z neurons to vibration of hindlimb extensor muscles in the decerebrate cat.

1. Small sinusoidal changes of length, applied longitudinally to the ddifferented GS muscle, were uused as a specific stimulus to activate the muscle spindle receptors in precollicular decerebrate cats. In order to determine the relative contribution of the primary and secondary endings of muscle spindles to the response of the nucleus z neurons, the effects of muscle vibration on this unit activity were studied under conditions in which the segmental monosynaptic reflexes produced by stimulation of the primary endings of muscle spindles were continuously monitored. 2. Vibration of the GS muscle (at 180-200/sec and amplitudes up to 250-320 mu) affected the frequency and pattern of discharge in 50 out of 168 units recorded from the lower medulla...