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At least 217 records · Page 12Linked to original sources
PubMed2002

Physiologic characteristics of cold perfluorocarbon-induced hypothermia during partial liquid ventilation in normal rabbits.

UNLABELLED: Because perfluorocarbon (PFC) liquid contacts closely with the alveolar capillaries during partial liquid ventilation (PLV), PLV with cold PFC may be used for the induction of hypothermia. Twenty rabbits were randomized to PFC-induced hypothermia (PH) (n = 7; core temperature 35 degrees +/- 1 degrees C), surface hypothermia (SH) (n = 7; 35 degrees +/- 1 degrees C), or normothermia (n = 6; 39 degrees +/- 1 degrees C). We induced PH by repeated in situ exchanges of 0 degrees C perfluorodecalin during PLV. At the establishment (0 min) of hypothermia in the PH group, oxygen consumption (P = 0.04) and oxygen extraction ratio (P = 0.01) decreased from normothermic condition. Metabolic (oxygen consumption, oxygen extraction ratio, serum lactate level) and hemodynamic variables (heart rate, blood pressure, cardiac output, pulmonary artery pressure) of the PH group were not different from those of the SH group at 0, 30, 60, 90, and 120 min of hypothermia. The difference in temperature between the pulmonary artery and rectum during the hypothermic period was smaller in the PH group compared with the SH group (P = 0.033). In conclusion, hypothermia may be induced during PLV by using cold PFC. This "pulmonary method" of cooling was comparable to a systemic method of cooling with regard to a few important physiologic variables, while maintaining a narrower interorgan temperature difference. IMPLICATIONS: The induction of moderate hypothermia was feasible in rabbits by administrating cold perfluorocarbon liquid into the lung. Physiologic changes induced by this pulmonary cooling were comparable to those induced by systemic cooling. Our method may be regarded as a methodological advance in the field of therapeutic hypothermia.

Animals↗
PubMed2004

Psychological and physiological characteristics of a proposed object-referral/self-referral continuum of self-awareness.

This research extends and confirms recent brainwave findings that distinguished an individual's sense-of-self along an Object-referral/Self-referral Continuum of self-awareness. Subjects were interviewed and were given tests measuring inner/outer orientation, moral reasoning, anxiety, and personality. Scores on the psychological tests were factor analyzed. The first unrotated PCA component of the test scores yielded a "Consciousness Factor," analogous to the intelligence "g" factor, which accounted for over half of the variance among groups. Analysis of unstructured interviews of these subjects revealed fundamentally different descriptions of self-awareness. Individuals who described themselves in terms of concrete cognitive and behavioral processes (predominantly Object-referral mode) exhibited lower Consciousness Factor scores, lower frontal EEG coherence, lower alpha and higher gamma power during tasks, and less efficient cortical preparatory responses (contingent negative variation). In contrast, individuals who described themselves in terms of an abstract, independent sense-of-self underlying thought, feeling and action (predominantly Self-referral mode) exhibited higher Consciousness Factor scores, higher frontal coherence, higher alpha and lower gamma power during tasks, and more efficient cortical responses. These data suggest that definable states of brain activity and subjective experiences exist, in addition to waking, sleeping and dreaming, that may be operationally defined by psychological and physiological measures along a continuum of Object-referral/Self-referral Continuum of self-awareness.

Adolescent↗
PubMed1994

Physiological characteristics of inferior vena cava pulse waveform during foetal development.

Non-invasive measurements of pulsatile diameter changes (pulse waveform) in the foetal inferior vena cava (IVC) during foetal development using an ultrasonic phase-locked echo tracking system with high sampling frequency (3000 Hz) are described. Successful human foetal IVC pulse waveform recording was achieved cross-sectionally in 56 out of 68 (82%) women at 20-23, 24-27, 28-31, 32-35, and 36-39 weeks' gestation. The pulse waveform in the foetal IVC consisted of four waves (A, X, V, and Y waves). An increase in the depth of the X and Y descents was observed during the second trimester. It was considered that this was due to the decrease in placental resistance. A slightly decreased foetal heart rate during the third trimester affected the time for right ventricular diastolic filling. Our findings indicate that the alterations in resistance to right ventricular afterload produced by growth in the placenta and right atrioventricular filling patterns with advancing gestational age are reflected in the foetal IVC pulse waveform. In addition, foetal systemic and placental vascular resistance profoundly influence right atrioventricular filling patterns. It is possible to record the foetal IVC pulse waveform simply, using a quite different ultrasound methodology (phase-locked echo tracking) from that used for normal pulse echo or Doppler measurements. Such studies provide important physiological information about the normal foetus.

Adult↗
PubMed2003

A recombinant polymeric hemoglobin with conformational, functional, and physiological characteristics of an in vivo O2 transporter.

With the objective of developing a recombinant oxygen carrier suitable for therapeutic applications, we have employed an Escherichia coli expression system to synthesize in high-yield hemoglobin (Hb) Minotaur, containing alpha-human and beta-bovine chains. Polymerization of Hb Minotaur through S-S intermolecular cross-linking was obtained by introducing a Cys at position beta9 and substituting the naturally occurring Cys. This homogeneous polymer, Hb Polytaur, has a molecular mass of approximately 500 kDa and was resistant toward reducing agents present in blood. In mice, the circulating half-time (3 h) was fivefold greater than adult human Hb (HbA). The half-time of autooxidation measured in blood (46 h) exceeded the circulating retention time. Hypervolemic exchange transfusion resulted in increased arterial blood pressure similar to that with albumin. The increase in pressure was less than that obtained by transfusion of cross-linked tetrameric Hb known to undergo renovascular extravasation. The nitric oxide reactivity of Hb Polytaur was similar to HbA, suggesting that the diminished pressor response to Hb Polytaur was probably related to diminished extravasation. Transfusion of 3% Hb Polytaur during focal cerebral ischemia reduced infarct volume by 22%. Therefore, site-specific Cys insertion on the Hb surface results in uniform size polymers that do not produce the large pressor response seen with tetrameric Hb. Polymerization maintains physiologically relevant oxygen and heme affinity, stability toward denaturation and oxidation, and effective oxygen delivery as indicated by reduced cerebral ischemic damage.

Animals↗
PubMedDate not supplied

[Physiological characteristics of the smooth muscles vessels of the small circle of blood circulation].

Now sireos problem of pulmonology there are the diseases connected with infringement of coordinated regulation of a tone of smooth muscles of vessels and airways of ways that conducts to dissociation of parameters haemodinamyc and ventilation of lungs and as consequence, to infringement airwave-perfusion attitudes. In the review features humoral regulation contractile activity of smooth muscles of vessels of a small circle of blood circulation, a role of endocellular alarm systems in these mechanisms, and endothelium, as the local modulator endocrine functions are considered. Disgusting muscles of a small circle are distinguished from the main vessels of the big circle of blood circulation with predisposition to the raised mechanical pressure. In spite of the fact that endothelium renders modulating relaxe influence on contractile answers of smooth muscles of vessels of a venous and arterial small circle of blood circulation at action corresponding vasoconstriction, pulmonary veins are capable to endothelium-dependent dilatation to a lesser degree, in comparison with pulmonary arteries. And, on the contrary, in absence endothelium, they are characterized with high sensitivity to vasopression to substances--serotonin, histamine, phenylephrine. Features of regulation smooth muscle pressure pulmonary an artery are shown in contractile reactions of its isolated segments in reply to influence beta-adreno agonist--isoprotherenol and phosphoesterase inhibitors. Though, increase in endocellular concentration cyclic nucleotides (cAMP and\or cGMP), on the standard representations, cannot explain growth of a mechanical pressure of smooth muscles, apparently, in contractile reactions of a pulmonary artery to influence biologically and physiologically active substances interfere more complex mechanisms in which basis processes of interaction of smooth muscles cells lay, endothelium and cells of a microenvironment. Finding-out of the contribution cyclic nucleotides in these processes demands the further researches.

Animals↗
PubMed2004

Subdivision of essential tremor patients according to physiologic characteristics.

OBJECTIVE: To test the effect of different forearm postures on tremor characteristics. We hypothesized that changes in tremor characteristics in relation to posture can subclassify essential tremor (ET) patients. METHODS: Fourteen ET patients were tested while seated and holding a full cup in three well-defined arm postures: 15 cm above the armrest, elbow at 90 degrees flexion and when the cup was near the mouth. Hand movements were recorded using a triaxial accelerometer. Concomitantly, we recorded surface electromyogram (EMG) signals from the wrist extensor muscles. Hand acceleration and the primary tremor frequency from the power spectrum were calculated for each posture in two independent trials. The coherence at the primary tremor frequency between the EMG and the accelerometry signals was calculated. RESULTS: ET patients could be classified into two groups: ET-1 (nine patients) had position-dependent peak frequencies while ET-2 (five patients) had position-independent peak frequencies. The latter group had significantly higher coherencies between EMG and accelerometry of tremor and insignificantly higher tremor amplitudes compared with ET-1. In both groups tremor amplitude increased when the hand was near the mouth. CONCLUSION: The results suggest that ET patients can be classified based on the position dependence of frequency and other physiologic properties.

Acceleration↗
PubMed1996

[A complex mathematical model of decompression based on biophysical and physiological characteristics].

In the devised integral mathematical model of decompression body tissues are expressed as sets of spectra of specific body tissue semi-saturation periods calculated from tissue circulation and corrected for gas diffusion through the skin. Values of permissible oversaturation were determined as a sum of critical and permissible supercritical oversaturations. The critical oversaturation of tissues is proportional to the cubic root from the ambient pressure, whereas the permissible supercritical oversaturation is a function of time constant of tissue desaturation and critical oversaturation. This decompression model incorporates specific models of tissue saturation and desaturation asymmetry due to difference in physical activities, ambient temperature and oxygen partial pressure in the breathing mixture during exposure and decompression. Besides, an equation to evaluate and control oversaturation in the combined venous blood was established and used in the model. Experiments showed that following decompression regimes calculated with this model, the level of gas formation in the combined venous blood was significantly lower than after application of decompression following similar regimes in the Diving Service Rules-85.

Biophysical Phenomena↗
PubMed1985

Thyroxine, triiodothyronine, reverse-triiodothyronine, and other physiological characteristics of periparturient cows fed restricted energy.

Eighty-six cows were assigned to two equal groups with group A fed according to National Research Council recommendations for total digestible nutrients for the 8 wk before parturition and group B was fed 21% higher energy in the first 6 wk and 15% higher in the last 2 preparturient wk. Thyroxine in blood serum decreased in both groups 14 days before and on the day of delivery. It was significantly lower in group A. Findings were similar with triiodothyronine. Blood serum concentrations of reverse-triiodothyronine of group A was significantly higher in group A on day 28 and 14 than group B before delivery. Energy intake had little influence on the serum concentrations of other constituents (albumin, total protein, immunoglobulin G, total and free cholesterol, nonesterified fatty acids). Restricted energy intake that does not alter thyrotropin-thyrotropin-releasing hormone secretion results in higher rate of production of reverse-triiodothyronine and in decreased serum concentration of triiodothyronine. Slight changes of energy balance might be indicated readily by reverse-triiodothyronine concentration in blood serum.

Animal Nutritional Physiological Phenomena↗
PubMedDate not supplied

[Behavioral and physiological characteristics of nonagouti mutation in gray rats during selection for aggressiveness].

The goal of this work was to find out to which degree the black coat color mutation nonagouti that appears in wild Norway rat in the course of breeding for the maintenance and enhancement of aggressiveness towards a human affects selected and other behavioral traits as well as stress reactivity and brain neurochemistry. Nonagouti rats displayed increased emotionality in the open-field and forced-swimming tests as compared to agouti animals, whereas there were no differences in anxiety estimated in the elevated plus-maze. Neither were there any differences in glucocorticoid reactions to a combined stressful procedure such as forced swimming. The dopamine content in the frontal cortex and striatum and noradrenaline content in the frontal cortex were increased in black rats as compared to gray rats. The result suggest that the nonagouti mutation in gray aggressive rats enhances the effects of selection for aggressiveness on some behavioral traits and brain catecholamine level.

Aggression↗
PubMed2005

Isolation by genetic and physiological characteristics of a fuel-ethanol fermentative Saccharomyces cerevisiae strain with potential for genetic manipulation.

Fuel ethanol fermentation process is a complex environment with an intensive succession of yeast strains. The population stability depends on the use of a well-adapted strain that can fit to a particular industrial plant. This stability helps to keep high level of ethanol yield and it is absolutely required when intending to use recombinant strains. Yeast strains have been previously isolated from different distilleries in Northeast Brazil and clustered in genetic strains by PCR-fingerprinting. In this report we present the isolation and selection of a novel Saccharomyces cerevisiae strain by its high dominance in the yeast population. The new strain, JP1 strain, presented practically the same fermentative capacity and stress tolerance like the most used commercial strains, with advantages of being highly adapted to different industrial units in Northeast Brazil that used sugar cane juice as substrate. Moreover, it presented higher transformation efficiency that pointed out its potential for genetic manipulations. The importance of this strain selection programme for ethanol production is discussed.

Acids↗
PubMed1972

Initiation of antibody responses by different classes of lymphocytes. V. Fundamental changes in the physiological characteristics of virgin thymus-independent ("B") lymphocytes and "B" memory cells.

The life-span and migratory characteristics of rat thoracic duct cells which initiate the adoptive primary and secondary antibody response to diphtheria toxoid (DT) and horse spleen ferritin (HSF) were investigated. The experimental results show that thoracic duct lymphocytes from normal (unimmunized) donors are able to restore the adoptive response of irradiated hosts to HSF. Thoracic duct cells passaged through an intermediate host (intravenous injection and subsequent collection in the thoracic duct lymph) showed a marked reduction in their restorative action as compared with unpassaged cells. In addition, the restorative action of cells from donors treated with thymidine-(3)H for 48 hr before cannulation of the thoracic duct was markedly decreased. This indicates that a population of lymphocytes involved in the adoptive primary response is unable to recirculate from the blood to the lymph and is turning over rapidly (short lived). The nonrecirculating, short-lived lymphocytes are proably "B" cells, since a combination of spleen cells from neonatally thymectomized rats and passaged or thymidine-(3)H-treated cells restores a vigorous response to HSF. On the other hand, passaged or thymidine-(3)H-treated thoracic duct cells from donors immunized to DT or HSF are able to restore a vigorous adoptive secondary antibody response. Experiments with the hapten-protein conjugate, DNP-DT, show that the majority of both helper ("T") and precursor ("B") cells are able to recirculate and are slowly turning over (long lived). The findings suggest that T lymphocytes involved in both the primary and secondary antibody response are recirculating, long-lived cells. However, B lymphocytes involved in the primary response are nonrecirculating, short-lived cells ("B(1)" cells) which undergo a fundamental physiological change to recirculating, long-lived cells ("B(2)" cells) involved in the secondary antibody response.

Aminocaproates↗
PubMed2005

Bt176 corn in poultry nutrition: physiological characteristics and fate of recombinant plant DNA in chickens.

A genetically modified Bt176 corn hybrid, which contains an insecticidal protein against the European corn borer, and its conventional, nonmodified counterpart were evaluated in 4 separate trials to verify substantial equivalence in feeding value and animal performance. Thirty-six individually kept laying hens and 3 replicates of 94 broiler chickens each, assigned to 12 cages, were fed 2 different hen and broiler diets containing either 60% conventional or 60% Bt176 corn. The nutrient compositions of the 2 corn hybrids and the 2 corn diets revealed no major differences. Furthermore, metabolism and performance data revealed no significant differences between the birds that received the conventional, nonmodified corn, and those that received the modified corn diets. The detection of the genetic modification, by PCR, in feed obtained from insect-resistant Bt corn, in tissues and products from animals fed Bt corn is described. In all evaluated chicken tissues of muscle, liver, and spleen, the corn-chloroplast ivr gene fragment was amplified. It can be deduced from these findings and from other studies that the transfer of DNA fragments into the body is a normal process that takes place constantly. Nevertheless, no recombinant plant DNA fragments such as recombinant bla or cry1A(b) fragments could be found. Bt-gene specific constructs from the Bt corn were not detected in any of the poultry samples, neither in organs, meat, nor eggs.

Animal Feed↗
PubMed1994

Some physiological characteristics of motor cortex neurons of aged rabbits.

Neurophysiological alterations occurring in the motor cortex of aged rabbits have been examined. Experiments were performed on rabbits of three age groups: one year old (young), four to five years old (middle-aged) and six to seven years old (aged). Extracellular unit activity was recorded in the motor projection of a forelimb. Several sessions of rhythmic (2 Hz) electrocutaneous stimulation were delivered to contralateral forelimb. The neuronal activity was recorded before and after rhythmic stimulation. We also measured the firing rate during spontaneous electromyogram activity of the extensor carpi radialis. Neurons having slow spontaneous firing activity were predominant in aged rabbits as compared with young animals. In young animals the highest values of spontaneous firing rate (15-20 impulses/s) were observed in neurons related to movement. In aged rabbits spontaneous firing rate of movement-related neurons did not exceed 16 impulses/s. During spontaneous movements of extensor carpi radialis, the level of neuronal activity in young rabbits was twice as high as that in aged ones. In young rabbits after rhythmic electrocutaneous stimulation of a forelimb, 20% of recorded neurons exhibited periodic fluctuations in firing rate with the period of preceding stimulation. The repeated stimulation sessions increased the number of rhythmic firing neurons to 40-50%. In aged rabbits, patterns of firing activity of motor cortex neurons did not change significantly after several sessions of rhythmic electrocutaneous stimulation. Decreased neuronal excitability may be the cause of functional alterations in motor cortex neurons of aged rabbits.

Aging↗
PubMed2006

Seasonal variations of physiological characteristics and thermal sensation under identical thermal conditions.

Seasonal variations of human thermal characteristics were inspected in thermal comfort and when constantly indoors. Metabolic rate, tympanic temperature, skin temperature, body fat, body weight and thermal sensation were measured under identical thermal conditions in a chamber over the course of one year. Experiments were carried out for each subject in both summer and winter. Six subjects were measured 35 times in summer and 45 times in winter. one subject was measured weekly for 14 months. Measurements for analyses were taken 40-60 min after entrance into the chamber. Results revealed the following. 1) For all subjects, the metabolic rate, tympanic temperature and body fat were lower in summer than in winter; thigh skin temperatures were higher in summer than in winter. The averaged individual ratio of seasonal difference was 11.9% for metabolic rate, 14.9% for body fat, 1.8% for thigh temperature and 0.53% for tympanic temperature. Seasonal differences of about 10% in metabolic rate were maintained in this study. 2) Seasonal variations of the variables were examined for phase relationships against the outdoor temperature. 2-1) Metabolic rate, thermal sensation, body weight and body fat changed in reverse phase, whereas skin temperature was in-phase. 2-2) Skin temperature lagged by about one month in both summer and winter. Body fat also lagged by about one month in summer, but corresponded to the phase in winter. Metabolic rates were also in-phase in winter but led about three months in summer. Thermal sensations lagged by about three months in winter but were in-phase in summer. Body weight was in-phase in summer and winter. 2-3) Summer disorders were observed particularly in seasonal variations of metabolic rates, tympanic temperature, skin temperatures, and thermal sensation, thereby suggesting that the effect of temperature exposure was altered by air-conditioner use.

Adipose Tissue↗
PubMed1987

Anatomical and physiological characteristics of vestibular neurons mediating the horizontal vestibulo-ocular reflex of the squirrel monkey.

The anatomical characteristics of vestibular neurons, which are involved in controlling the horizontal vestibulo-ocular reflex, were studied by injecting horseradish peroxidase (HRP) into neurons whose response during spontaneous eye movements had been characterized in alert squirrel monkeys. Most of the vestibular neurons injected with HRP that had axons projecting to the abducens nucleus or the medial rectus subdivision of the oculomotor nucleus had discharge rates related to eye position and eye velocity. Three morphological types of cells were injected whose firing rates were related to horizontal eye movements. Two of the cell types were located in the ventral lateral vestibular nucleus and the ventral part of the medial vestibular nucleus (MV). These vestibular neurons could be activated at monosynaptic latencies following electrical stimulation of the vestibular nerve; increased their firing rate when the eye moved in the direction contralateral to the soma; had tonic firing rates that increased when the eye was held in contralateral positions; and had a pause in their firing rate during saccadic eye movements in the ipsilateral or vertical directions. Eleven of the above cells had axons that arborized exclusively on the contralateral side of the brainstem, terminating in the contralateral abducens nucleus, the dorsal paramedian pontine reticular formation, the prepositus nucleus, medial vestibular nucleus, dorsal medullary reticular formation, caudal interstitial nucleus of the medial longitudinal fasciculus, and raphé obscurus. Eight of the cells had axons that projected rostrally in the ascending tract of Deiters and arborized exclusively on the ipsilateral side of the brainstem, terminating in the ipsilateral medial rectus subdivision of the oculomotor nucleus and, in some cases, the dorsal paramedian pontine reticular formation or the caudal interstitial nucleus of the medial longitudinal fasciculus. Two MV neurons were injected that had discharge rates related to ipsilateral eye position, generated bursts of spikes during saccades in the ipsilateral direction, and paused during saccades in the contralateral direction. The axons of those cells arborized ipsilaterally, and terminated in the ipsilateral abducens nucleus, MV, prepositus nucleus, and the dorsal medullary reticular formation. The morphology of vestibular neurons that projected to the abducens nucleus whose discharge rate was not related to eye movements, or was related primarily to vertical eye movements, is also briefly presented.

Abducens Nerve↗
PubMed1993

Morpho-physiologic characteristics of Escherichia coli and Shigella flexneri 2a carrying the htpR15 gene.

Electron microscopic examination of the morphology of normal Escherichia coli MC4100 and Shigella flexneri cells and their htpR-defective recombinants has shown the presence in the latter of noncrystalline granules after growth at 37 degrees C. The defect of the htpR gene leads to some changes in ultrastructure of bacterial colonies and the intensification of the processes of development and aging of colonies as integral structures. These phenomena are manifested by early formation of intercellular contacts and thick surface films as well as the enhanced destruction of microorganisms. The recombinant Shigella strain grown at 30 degrees C retained its ability to provoke keratoconjunctivitis.

Escherichia coli↗