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Biomedical subjects

Z Tomori

Publications and source records attributed to Z Tomori.

At least 37 records · Page 2Linked to original sources
PubMed1999

Interaction of sleep apnoea syndrome with various diseases.

Sleep disordered breathing (SDB), particularly their clinically most serious and at the same time common form-sleep apnoea syndrome-caused by structural or functional abnormalities in the area of upper airways, are frequently linked with other diseases. The accompanying respiratory, cardiovascular, neuropsychic, sympathoadrenal and endocrine-metabolic disorders and their variable intensity determine the character and severity of patients complaints. The coincidence of SDB with alteration in one or another system produces mutual potentiation of their negative effects appearing as serious, not rarely even life threatening acute complications or chronic consequences manifesting exactly in the area of the afflicted system. The paper illustrates on several examples the development of pathological signs of SDB concerning practically all medical branches and at the same time demonstrating the multidisciplinary character of sleep medicine. (Fig. 1, Ref. 27.)

Humans↗
PubMed1998

Mechanisms and clinicophysiological implications of the sniff- and gasp-like aspiration reflex.

Mechanical stimulation of the pharyngeal mucosa in cats and some other mammals evokes the 'aspiration reflex' (AR) characterized by rapid and strong inspiratory efforts not followed by active expirations. It resembles other spasmodic inspiratory acts such as the sniff, the gasp, and the sigh in several aspects, e.g. reflex or semireflex triggering from the upper airways, the sudden onset and termination of such inspirations, the massive recruitment, steep rise and high-peak amplitude of inspiratory unit activity, analogous ventilatory pattern, and contribution to arousal. The similarity of these spasmodic acts is manifested mainly in enhanced speed and volume of inhalation, although of different intensity, which is determined by the varying degree of forced inspiratory activity and a concomitant inhibition of expiratory activity. The extent of the inspiratory dilation of the glottis and the timing and range of late-inspiratory and/or postinspiratory glottal narrowing modulate the depth of aspiration. Thus, the inhalation can be moderate as in sniffing, which provides a transfer of odorants to the olfactory mucosa. In AR the airstream is presumably strong enough to tear off the mechanical particles from the naso- and oropharynx and to convey them into the hypopharynx to allow their subsequent elimination by reflex swallowing or coughing. Prolonged glottal opening allows either the transfer of some additional air to the bronchi by sighing to prevent the development of atelectasis, or redistribution of a larger amount of fresh air into the lungs by gasping to support autoresuscitation. Should aspiration be a common effective component in these spasmodic processes, then the easily elicitable AR could be beneficial as a simple model for studying their properties in health and disease.

Animals↗
PubMed1998

The interfacial behavior of cytochrome c studied by pendant-drop technique.

The adsorption properties of cytochrome c (cyt c) were characterized by surface tension measurements using the pendant-drop method employing the digital image analysis of the drop shape. The method was applied to the study of the protein conformation change due to acidification at low ionic strength. The observation of the saturated steady-state surface tension shows that decrease in pH induces its cooperative change centered around pH 2.5. This value is equal to the value of apparent pK of the acid-induced transition of the horse ferricyt c from a native state to the unfolded conformation. This indicates that the saturated steady-state surface tension is sensitive to the conformation of cyt c in bulk phase, and the pendant-drop method might be used to monitor changes in the tertiary structure of proteins.

Adsorption↗
PubMed1997

Effect of polyglutamate on the thermal stability of ferricytochrome c.

The effect of saturated solutions of polyglutamate on the thermal stabilities of the Met-80-heme iron bond and of the ferricytochrome c as a whole were studied by absorption spectroscopy and differential scanning calorimetry at pH 7.0. According to spectral data the midtransition temperature of the cleavage of the sulfur-iron bond was 57.4 +/- 0.5 degrees C and 66.8 +/- 0.5 degrees C for cytochrome c and cytochrome c-polyglutamate complex, respectively. Addition of polyglutamate to cytochrome c at pH 7.0 alters the denaturation properties of the protein. As follows from DSC scans, the denaturation temperature for cytochrome c is decreased from 85.4 +/- 0.2 degrees C to 68.7 +/- 0.2 degrees C in the presence of the saturated amount of polyglutamate. The protein stability in terms of Gibbs energy change at protein unfolding amount to delta G(25 degrees C) = 22.7 +/- 2.7 and 32.0 +/- 2.2 kJ/mol, for cytochrome c and cytochrome c-polyglutamate complex, respectively, at pH 7.0. It is evident that polyglutamate increases the thermal stability of the sulfur-iron bond and decreases the denaturation temperature of the cytochrome c molecule as a whole. The complex thermal stability in terms of Gibbs energy is not lower than that of cytochrome c in the range of physiological temperatures.

Animals↗
PubMed1997

[Sleep-related breathing disorders--an interdisciplinary topic in undergraduate and postgraduate medical education].

Sleep-related breathing disorders (SRBD) include several disorders gradually developing from simple and loud snoring through upper airway resistance syndrome and sleep apnoea up to the Pickwickian syndrome. They are manifestant as a respiratory distress and apnoeic episodes, desaturation of oxygen in the blood and interruption of sleep. These symptoms are demonstrated in a case of a patient with the Pickwickian syndrome. SRBD may result in severe secondary life-threatening cardiovascular complications (nocturnal arrhythmias, sudden cardiac death, stroke and pulmonary oedema). They may contribute also to the development of important disorders of public health such as hypertension, obesity, and traffic accidents resulting from hypersomnolence and fatigue. (Tab. 1, Fig. 3, Ref. 46.)

Adult↗
PubMed1997

[Disorders of heart rhythm and ECG changes in experimental apneic states].

BACKGROUND: Apnoeic events are often accompanied by various disturbances in electric cardiac activity, the character and development as well as mechanism of which remain broadly unknown suggesting both direct metabolic defects as well as neurogenous autonomic influences. METHODS: Changes in ECG and heart rate induced by repeated short-lasting inhalation of hypoxic poikilocapnic mixtures (100% N2 and/or 0.5-1% CO2 or 6% CO2 in N2) were analyzed in 17 spontaneously breathing cats anaesthetized with sodium pentobarbitone (40 mg.kg-1i.p.). RESULTS: N2 inhalation evokes hypoxaemic hyperventilation progressing into apnoea and bradycardia with secondary low-level atrioventricular conduction block and ischaemic changes in ECG. Contrary to this reversible respiratory failure, hypoxaemic hypercapnic hyperventilation and apnoea evoked by inhalation of 6% CO2 in N2 or 100% CO2 were accompanied by very marked additional effects of hypercapnia and acidosis. They appeared earlier and were more severe (high-level AV conduction block and premature contractions) suggesting direct myocardial alteration due to acidosis. CONCLUSIONS: The results provide experimental data for better understanding the dynamics, intensity and development of dysrhythmias and ECG changes occurring in two different types of cardiorespiratory failure in animal experiments as well as in central and obstructive types of sleep apnoea and other apnoeic events in humans. (Fig. 3, Ref. 27.)

Animals↗
PubMed1995

Power spectral analysis of respiratory responses to pharyngeal stimulation in cats: comparisons with eupnoea and gasping.

1. Based on similarities between properties of gasping and the aspiration reflex, we hypothesized that this reflex activates the central pattern generator for gasping. To evaluate this hypothesis, we have analysed high-frequency oscillations in phrenic and hypoglossal neural activities. These oscillations, analysed by power and coherence spectra, are considered as signatures of the central pattern generators for automatic ventilatory activity. 2. In decerebrate, vagotomized, paralysed and ventilated cats, the aspiration reflex was elicited in eupnoea and gasping by mechanical stimulation of the pharynx and electrical stimulation of the glossopharyngeal nerve. 3. Compared with eupnoeic values, the peaks in the power spectra occurred at higher frequencies in spontaneous gasping. Peaks in the coherence spectra showed identical changes. 4. Power and coherence spectra of inspiratory neural activities during the aspiration reflex differed markedly from those of eupnoea, but were similar to those in gasping. 5. We conclude that mechanical stimulation of the pharynx or electrical stimulation of the glossopharyngeal nerve activates a reflex by which the central pattern generator for eupnoea is depressed, and that for gasping is activated. Our results also support the concept that separate brainstem mechanisms generate ventilatory activity in eupnoea and gasping.

Animals↗
PubMed1995

Medullary neuronal activities in gasping induced by pharyngeal stimulation and hypoxia.

We examined the hypothesis that medullary respiratory-related and non-respiratory-related neuronal activities are similarly altered with the "aspiration reflex", induced by mechanical stimulation of the epipharyngeal mucosa, and gasping, induced by severe hypoxia. Extracellular neuronal activities were recorded in decerebrate, paralyzed and ventilated cats. Phrenic activity and neuronal activities were monitored in eupnea and gasping. Seventy-one unit activities were recorded in the lateral medulla including the nucleus tractus solitorii (NTS), lateral tegmental field (LTF) and the nucleus ambiguus (NA). The respiratory modulation of a neuronal activity was quantified by a eta 2 statistic (Orem, J. and Dick, T., 1983, J. Neurophysiol. 50: 1098-1107). The eta 2 values of the units ranged from 0.02 to 0.93. Inspiratory-related activities with relative high eta 2 values (n = 16) were recorded in the region closed to the NTS. Phase-spanning (n = 7) and expiratory-related activities (n = 10) were recorded in the ventral medullary region. Units with low eta 2 values (n = 29) and with no spontaneous activity (n = 9) in eupnea were recorded in the region of the LTF. In both "aspiration reflex" and gasping, inspiratory-related activities were augmented and expiratory-related activities were suppressed. Tonic units were activated and additional activities were recruited. The modulation of the neuronal activities to gasping induced by anoxia was identical to that induced by pharyngeal stimulation in either hyperoxia or severe hypoxia. We concluded that medullary gasping mechanism is recruited by pharyngeal stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

The sniff-like aspiration reflex evoked by electrical stimulation of the nasopharynx.

Forced inspiratory efforts resembling the sniff-like aspiration reflex (AR) were evoked by single-shocks or trains of electrical impulses to the dorsal pharyngeal and nasal mucosal surfaces in 12 anaesthetized spontaneously breathing cats. The strongest ARs determined by diaphragmatic (DIA) EMG and peak-inspiratory flows were elicited from the dorsolateral nasopharyngeal wall close to the torus tubalis. Highly responsive sites were also detected in the posterolateral nasal cavity and in the rostrolateral oropharynx. Repetitive stimulation at threshold strength evoked ARs exclusively in the late inspiration and early expiration. Suprathreshold responses abolished and replaced the tidal respiration. ARs exhibited a two-phase response in DIA EMG: a short latency (25.2 +/- 2.4 msec, M +/- SD) powerful excitation (69.7 +/- 10.7 msec) followed by an voltage-dependent inhibition (63.9 +/- 11.3 msec). Irrespective of voltage repetitive ARs were attenuated at rates above 7-9 Hz. In conclusion, electrical stimulation within the large receptive area of the nasal-pharyngeal airway evokes sniff-like efforts with biphasic inspiratory pattern and marked phase-dependent properties.

Animals↗
PubMed1995

Reflex reversal of apnoeic episodes by electrical stimulation of upper airway in cats.

Respiratory effects of electrical stimulation of the upper airways (UAW) before and during apnoeic episodes induced by nitrogen inhalation were studied in 9 anaesthetized cats. In eupnoeic animals these electrically-evoked reflexes comprise rapid and powerful inspiratory efforts characterized by strong maximal airway occlusion pressures (Pmax = 635 +/- 39 mm H2O) and rapid peak inspiratory flow rates (PIF = 536 +/- 36 ml.sec-1) similar to the sniff-like aspiration reflex elicited mechanically. Electrical stimulation of the UAW mucosa can elicit reflex inspirations and sniff-like aspiration reflexes even during reversible hypoxic apnoea but their intensity and reproducibility are transiently reduced. When repeated adequately, the electrically-induced reflexes can increase the reactivity of respiratory centre and interrupt or terminate apnoeic episodes as do other types of UAW stimulation. Reflex mechanisms and respiratory centre activations seem to be involved in these effects. The results suggest that electrical stimulation of UAW could be useful for testing the respiratory centre reactivity as well as for reflex reversal of apnoeic episodes and restoration of normal breathing in animal experiments and clinico-physiological studies. Such investigation of the role of UAW reflexes in the pathogenesis and therapy of apnoeic syndromes might also be possible by using a cardiostimulator adapted as respiratory pacemaker.

Animals↗
PubMed1994

Reflex recruitment of medullary gasping mechanisms in eupnoea by pharyngeal stimulation in cats.

1. Mechanical stimulation of the naso- and oropharynx causes the replacement of the eupnoeic ventilatory pattern by a brief, but large, burst of activity of the phrenic nerve. Our purpose was to define whether these changes in phrenic activity represent a switch to gasping. 2. In decerebrate, vagotomized, paralysed and ventilated cats, mechanical stimulation of the pharynx was performed during eupnoea, apneusis and gasping. The latter two ventilatory patterns were produced by ventilating the experimental animal with 1.0% carbon monoxide in air or with 100% nitrogen. Eupnoea could be re-established by a recommencement of ventilation with oxygen. 3. The rate of rise of phrenic activity and its peak height were much greater following mechanical stimulation of the pharynx than the phrenic bursts of eupnoea or apneusis. The durations of phrenic burst and the period between these were much less following pharyngeal stimulation. In contrast, these variables of phrenic activity were the same during pharyngeal stimulation and in gasping. 4. Previous studies had established that activity within a region of the lateral tegmental field of medulla is critical for the manifestation of gasping. Hence, electrical stimulation of this region during gasping elicits premature gasps whereas its ablation irreversibly eliminates gasping. 5. We positioned a multibarrelled pipette in the critical medullary region for gasping. Its location was verified, once gasping was established in hypoxia or anoxia, by the elicitation of premature gasps following electrical stimulation. Neurons in this region were destroyed by microinjections of the neurotoxin kainic acid; in a few experiments the region was destroyed by electrolytic lesions. 6. Following destruction of the region of the lateral tegmental field, gasping could no longer be provoked in anoxia. In contrast, the eupnoeic pattern of phrenic activity continued. However, mechanical stimulation of the pharynx no longer caused any changes in the on-going pattern of phrenic activity. 7. We conclude that mechanical stimulation of the pharynx elicits a powerful reflex by which eupnoea is suppressed and gasping is elicited. Stated differently, the changes in phrenic activity during this pharyngeal stimulation in fact represent gasps. 8. Gasps are dependent upon activity within a region of the lateral tegmental field of the medulla. This region plays no role in the neurogenesis of eupnoea. Hence, our results provide additional support for the concept that there are multiple sites for ventilatory neurogenesis in the mammalian brainstem.

Animals↗
PubMed1994

Sniff-like aspiration reflex evoked by pressure pulses from the upper airways in cats.

Respiratory effects of single positive and negative pressure pulses (PPP, NPP) applied to the functionally isolated upper airways (UA) were studied in 11 anaesthetized cats breathing spontaneously through a tracheal tube. The UA pressure and the changes of tracheal airflow were recorded and the blood pressure and electrocardiogram were occasionally monitored. Sniff-like aspiration reflexes comprising powerful spasmodic inspirations could be elicited by PPP or NPP of 20 to 110 cm H2O or -14 to -140 cm H2O. The responses to NPP but also to PPP characterized by high peak inspiratory flow, mean inspiratory flow and tidal volume (PIF = 312.5 +/- 64.3 and 231.1 +/- 21.7 ml.sec-1; VTI = 178.3 +/- 46.7 and 110.1 +/- 14.4 ml.sec-1; VT = 40.9 +/- 8.3 and 22.5 +/- 1.7 ml) resembled closely the aspiration reflex elicited by mechanical stimulation of the pharyngeal wall. Occasionally, sneezing, minor modifications of breathing pattern and solitary forced inspirations could be induced by lower pressures. The results indicate that sudden pressure stimulation of the UA evokes vigorous respiratory responses including the aspiration reflex. These reflexes and their alterations may contribute to development or release of both UA obstruction and apnoea, at least in cats.

Animals↗
PubMed1993

[Computer evaluation of respiratory changes during acute hypoxia in an experimental model].

Experiences are presented concerning the use of a computer system in analyzing the dynamics of respiratory changes during reversible respiratory failure induced by inhalation of nitrogen in anesthetized cats. The main focus is on semiautomatic evaluation of the air flow signal during experimentally induced hypoxia in model experiment. On the basis of experience with computer aided evaluation of respiratory changes in over 40 animals and regarding the analysis of actual data obtained from 29 hypoxic episodes leading to reversible respiratory failure in 9 cats, advantages and pitfalls of evaluating respiration parameters by the breath-by-breath method are highlighted. Besides demonstrating the applied computer processing of data, the paper evaluates the most important of the 30 respiratory parameters studied, i.e. tidal volume (VT), minute ventilation (VE), inspiratory time (TI), and the ratios VI/TI and TI/TTOT. The results allow to quantify well the dynamics of development of changes of the respiratory model particularly during the first phase of acute hypoxic hypoxia. (Tab. 1, Fig. 5, Ref. 21).

Acute Disease↗
PubMed1993

Comparison of inspiratory effort in sniff-like aspiration reflex, gasping and normal breathing in cats.

The changes in airway occlusion pressure and airflow, occurring during two spasmodic breathing patterns, were studied and compared with normal breathing pattern in 12 anaesthetized cats. The inspiratory effort developed during the sniff-like aspiration reflex elicited by mechanical stimulation of the nasopharynx under control conditions proved to be very similar in character and intensity to the activity observed during gasping which occurred on resuscitation, of the same cats, from hypoxic apnoea. The starting (P50) and maximum (Pmax) airway occlusion pressure developed in these two spasmodic breathing patterns were very high. Extremely rapid rates of contraction and relaxation were detected by computer-assisted measurements of dynamic changes in both the pressure values and the slopes of pressure curves. The results suggest common effector mechanisms, reflecting similar forceful inspiratory drives, for the aspiration reflex and gasping. These two spasmodic processes differ substantially from normal breathing. Nevertheless, the aspiration reflex differs from gasping in that it can be elicited by activation of upper airway afferents during eupnea. Moreover, as yet, there is no definitive evidence that the brainstem mechanisms responsible for generating the aspiration reflex are the same as those of the gasp. The main benefits of this reflex are its rather easy elicitability under various conditions and its capability to induce important cardiorespiratory effects (e.g.) reversal of central apnoea) owing to its powerful activity.

Airway Resistance↗
PubMed1991

Reversal of apnoea by aspiration reflex in anaesthetized cats.

Various flow and timing characteristics of breathing as well as electrocorticographic (ECoG) records were analysed in a model of reversible respiratory failure induced by N2 inhalation in 27 anaesthetized cats. During the first minute of respiratory arrest, nasopharyngeal stimulation by an elastic nylon fibre elicited a typical sniff- or gasp-like aspiration reflex (in 88.8% of cases), whilst similar tracheobronchial irritation evoked a weak cough reaction in one third of cases (34.2%). The aspiration reflex could also be evoked in progressive stages of apnoea characterized by very low and even isoelectric ECoG activity immediately before imminent irreversible respiratory failure, and it could interrupt and replace the periodic gasping sometimes occurring during apnoea. The reflex, comprising powerful inspiration efforts, could be evoked during apnoea many times in succession. Repeated aspiration reflexes alone resulted in recovery from hypoxic apnoea with gradual normalization of ECoG and subsequent restitution of spontaneous breathing even more frequently than it occurred in periodic gasping. Successful resuscitation from hypoxic apnoea by the aspiration reflex in cats suggests that nasopharyngeal stimulation can affect the mechanisms underlying the failure and restitution of breathing at least in some forms of apnoea.

Animals↗
PubMed1991

Hypoxic apnoea induced by N2 inhalation can be reversed by the aspiration reflex in anaesthetized cats.

Various cardiorespiratory and electrophysiological parameters were analysed in a model of acute respiratory failure induced by inhalation of pure nitrogen in approximately 150 anaesthetized cats. Initial hyperventilation leading to apnoea was characterized by extreme hypoxaemia, marked bradycardia and flattening of electrocortical (ECoG) activity. Artificial ventilation applied at the stage of marked mydriasis usually spontaneously prevented cardiovascular failure and normalized vital functions. Up to seven successive apnoeic attacks could be induced in the same cat. During the first 30 or 60 s of apnoea, nasopharyngeal stimulation usually elicited a typical gasp-like aspiration reflex, while tracheobronchial stimulation provoked a weak cough only in 28 and 34% of cases for 30- and 60-s apnoea, respectively. The aspiration reflex could be elicited at very low and even isoelectric ECoG activity, and its periodic provocation (without artificial ventilation) resulted, more frequently than did gasping, in recovery from hypoxic apnoea. Arousal and resuscitation induced by the aspiration reflex can provide a useful model to study the mechanisms of reversible respiratory failure and restitution of vital functions.

Administration, Inhalation↗
PubMed1991

[The effect of smoking and alcohol on decreased reaction time and mental arithmetic].

Simple reaction time to acoustic and visual signals and reaction time in combination with mental arithmetic were measured by means of an adjusted microcomputer in 16 healthy volunteers--university students. The over 1,200 tests performed yielded the following results: 1) Smoking of two consecutive cigarettes or peroral intake of 0.9 ml/kg of 48% alcohol not only failed to accelerate simple reaction time but even slowed it down. 2) Alcohol in the doses administered tended to slow down also the reaction time combined with mental arithmetic. 3) After smoking two cigarettes mental arithmetic was not significantly changed. 4) The applied method proved to be very suitable for testing psychophysiological effects of substances affecting the CNS and can be recommended for studying changes in motor and psychic functions. (Fig.3,Ref.38.).

Adult↗