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Biomedical subjects

I Baciu

Publications and source records attributed to I Baciu.

At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

Undersea psychophysiologic reactions of human organism.

The determinations carried out on 12 divers during the immersion into the sea to a depth between 7 and 29 m, as well as on controls in immersions at 4 m revealed a significant prolongation of the visual reaction time and a marked tachycardia. The changes were more marked at great depths and if exercise was superimposed over hyperbaric stress. A rise in the urinary excretion of 17-HOCS and vanillylmandelic acid and an impairment of the manual dexterity were also found during immersions. The results stress the importance of divers' monitoring during their underwater activity and the necessity of improving their physical training.

17-Hydroxycorticosteroids↗
PubMedDate not supplied

Renal mechanisms in erythropoiesis regulation.

The kidneys, which a high content of renal erythropoietic profactor, represent an important organ in the formation of erythropoietin in hypoxia. There is, however, an extrarenal mechanism, too, for its formation. The mechanism of erythropoietin secretion could be a central nervous action of hypoxia and a direct cellular one. In the first situation, moderate hypoxia acts upon the nervous centers, whose connexions with the effector cells are made by the beta-adrenergic sympathetic nerves, determining the release in certain kidney cells and in structures outside this organ, of the proerythropoietic factor of lysosomal nature. In the second situation, long-term intense hypoxia would exert its action directly on the cells, releasing the profactor participating in the formation of erythropoietin from the kidney lysosomes or those of other organs.

Animals↗
PubMedDate not supplied

Influence of bilateral olfactory bulbectomy on the circadian rhythm of phagocytic activity and phagocytic response in mice.

The bilateral olfactory bulbectomy (OB) has been proposed as an animal model of depression. The present study, carried out on NMRI adult male mice kept on a natural LD 12:12 regimen, aimed to assess the influence of OB on the circadian rhythm of blood neutrophils phagocytosis. The results show that OB mice present an about 20% reduction of the basal phagocytic activity at 09.00 hrs, 15.00 hrs. and 21.00 hrs. and a 40% reduction at 03.00 hrs., leading to a flattened circadian phagocytic curve. The results indicate that bilateral olfactory bulbectomy depresses phagocytosis, alters its circadian rhythm and consequently increases susceptibility to infections.

Animals↗
PubMedDate not supplied

Circadian rhythm of phagocytosis in mice.

There has been reported, in some diurnal or equivocal species (man, respectively guinea pig), a circadian rhythm of the phagocytic activity of blood neutrophils, with an acrophase occurring at the end of the light span. The present study, carried out on NMRI adult male mice kept on a LD 12:12 regimen, aimed to assess any circadian variation in the blood neutrophils' phagocytosis level. Basal phagocytic activity was tested against E. coli, every three hours of a 24 h cycle. The results show that phagocytosis in mice's blood neutrophils also presents a rhythmic circadian variation, whose acrophase is delayed with about eight hours compared to that in man, occurring in the second half of the dark period (3:00 h). The occurrence of high circadian phagocytic levels appears to be correlated with the activity type of the species and, of this point of view, mice cannot be used as a model for chronotherapeutical approaches in humans, without keeping in mind the differences between the time structure of the two species.

Animals↗
PubMedDate not supplied

High glucose concentrations increase the tumor necrosis factor-alpha production capacity by human peripheral blood mononuclear cells.

The proinflammatory cytokines tumor necrosis factor-a (TNF) and interleukin-1b (IL-1) play an important role in the pathogenesis of insulin-dependent diabetes mellitus, while TNF is also involved in promoting insulin resistance. It has been recently shown that glucose can induce the synthesis of TNF and IL-6 in human monocytes. The aim of the present study was to investigate the effect of glucose on unstimulated and lipopolysaccharide (LPS)-induced TNF and IL-1 production by human peripheral blood mononuclear cells (PBMC). No effect of glucose on spontaneous release of TNF or IL-I could be observed. The LPS-stimulated production of TNF was enhanced when cells were preincubated with increasing glucose concentrations. In contrast, no effect of glucose preincubation on LPS-induced IL-I synthesis was found. In conclusion, high glucose concentrations can increase the stimulated TNF production capacity, with possible important consequences for patients with diabetes mellitus.

Diabetes Mellitus, Type 1↗
PubMedDate not supplied

The brain and other sites of erythropoietin production.

Ischemic hypoxia of the head induced in dogs by carotid compression produces EPO secretion, upon direct cerebral stimulation, and adaptive carotid-respiratory reflexes via sino-carotid stimulation. During hypoxic hypoxia, there also occurs extrarenal EPO production, as shown in binephrectomized rats compared to controls. Ischemic hypoxia of a single kidney transplanted in the neck area (the other kidney being removed) does not induce EPO secretion. An additional factor, of extra-renal origin, is required for the renal production of EPO in a non-hypoxic organism. Section of the spinal cord at C6 level in rats does not abolish EPO secretion induced by hypobaric hypoxia, a fact that suggests that there is no nervous center to control EPO release into a peripheral organ, but EPO might be produced in the brain itself, possibly crossing the blood-brain barrier to reach the blood flow. Stereotactical attempts to locate nervous centers of erythropoiesis regulation also failed. EPO secretion obtained by electrical stimulation of different brain areas suggests the existence of widespread secretory cells, which might be the astrocytes. EPO production along the lymph-forming territories and the involvement of the lining macrophages is reported.

Animals↗
PubMedDate not supplied

Phagocytic response in rats following chemical sympathectomy with 6-hydroxydopamine.

Wistar rats were injected i.p. at 2, 4 and 7 days after birth with 6-OHDA (50 mg/kg). At maturity the phagocytic response of neutrophils was elicited by Escherichia coli (EC) lipopolysaccharide (LPS). Before and at 3 and 24 hours after the injection of LPS (1 mg/kg i.v.) the leucocyte (L) and neutrophil (N) counts and the phagocytic activity of N in blood against EC have been tested. In controls (6 female and 7 male rats) the number of N increases significantly after 3 h. The L and N responses were similar in controls and in treated (SyX) animals. In controls the percentage of phagocytic active N(PA) and the number of bacteria incorporated by 100 n(IB) shows significant rises at 3 h. In the SyX groups (7 females and 7 males) PA does not increase; the IB decreases significantly in females at 3 and 24 h. In conclusion chemical sympathectomy depresses the PR to LPS in rats; this suggests a stimulatory action of the sympathetic system on the phagocytic immune reaction. An immunological sexual dimorphism exists.

Animals↗
PubMedDate not supplied

The role of nervous mechanisms in the immune response.

This review presents the results of experimental researches performed in the last decades by Cluj-Napoca physiologists, concerning the role of hypothalamic nervous centers in the triggering of the nonspecific (phagocytic reaction) and specific (primary and secondary) immune response. The following methods aiming to explore the involvement of the hypothalamic vegetative nervous centers have been applied: section of the spinal cord, somatoencephalic humoral isolation with preservation of spinal cord, stimulation or lesions under stereotaxic control of some hypothalamic areas, conditioned reflexes, electroconvulsant shocks. The results show that nervous centers from the tuberal area and from the posterior hypothalamus are involved in the regulation and integration of the immune response considered as a homeostatic function, in connexion with a preoptic, anterior and lateral hypothalamic area, with a receptive function to antigens and their endogenous products. The activation of phagocytosis (phagocytic response) can be elicited in dogs by electrical stimulation of the tuberal area and inhibited by section of the spinal cord, or by barbiturates. The specific immune response is moderately neuromodulated for antigens, as heterospecific red cells and more intensely for Salmonella and especially for the influenza virus. These results could allow an integration of other analytical data of cellular and molecular biology of immunity wider functional concept.

Animals↗
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The sympatho-adrenal response and erythropoietin production in adaptation to hypoxia.

The research activity upon erythropoiesis regulation carried out by the team in the Physiology Department and in the Institute of Medical Research of the Romanian Academy in Cluj-Napoca developed continuously after 1950. Our studies contributed to the isolation, identification and characterization of erythropoietin (Epo) and also to a better understanding of the nervous adaptation mechanisms to hypoxia. At present, it is well known that hypoxia acts upon erythropoiesis through Epo production. Direct central nervous stimulation through hypoxia induces, via a neuro-humoral mechanism, a sympatho-adrenal response and release of Epo. Adaptive polyglobulia as a response to hypoxia increases the capacity of oxygen binding and transport. In this paper we attempted to identify the role of the sympathetic nervous system in adaptation to hypoxia correlated with Epo secretion. Experiments were carried out in three groups of rats, respectively, with cervical, thoracic, and lumbar (without celiac) sympathectomy. The sympathectomized animals were submitted to hypobaric or to hemorrhagic hypoxia, in parallel with control groups. Erythrocytic parameters (red blood cells, reticulocytes, hematocrit, and haemoglobin) were repeatedly assayed during the following 2-4 weeks. The results showed that animals with cervical sympathectomy adapt in a deficient manner to hypoxia; lacking the adaptive sino-carotid reflexes, adaptation occurs through increased Epo secretion, animals with cervical sympathectomy having higher counts of reticulocytes and of red blood cells at the end of experiment than intact animals. Thoracic sympathectomy has little influence upon the erythrocytic response, as the largest part of the respiratory and circulatory sympathetic reactions occur via the cervical sympathetic nerve. Lumbar sympathectomy without removal of the celiac ganglion does not decrease the erythrocytic response as expected; on the contrary, the erythrocytic response is increased as compared to controls.

Adaptation, Physiological↗
PubMedDate not supplied

Circadian phagocytic activity in rats under light-dark and constant light regimens.

The phagocytic function was proved to be a periodic, circadian process. Its acrophase appears to be differently timed in species with different activity type, occurring in the evening in diurnal species and at night in nocturnal ones. The main pineal hormone melatonin, whose secretion occurs strictly at dark, has been shown to play a role in the control of inflammation and to exert a certain stimulatory effect upon phagocytosis in vitro. The aim of the present study was to assess whether the phagocytic activity of neutrophils in the blood of rats exhibits a circadian rhythmicity similar to that of other nocturnal rodents (mice) and also if a constant light regimen alters its amplitude and/or chronostructure. Wistar rats were submitted to either an artificial light-dark 12/12 regimen (LD) or to constant light (LL), for 15 days. In vitro phagocytosis of the neutrophils in whole blood against E.coli was assessed at 10:00, 16:00, 22:00, and 04:00 hours. In LD, phagocytosis appears to be a rhythmical function, with statistically significant differences between the highest value at 04:00 hrs and the lowest at 10:00 hrs. Constant light induces a 30% depression of the phagocytic ability throughout the whole 24 hours cycle, without altering its oscillations. The darkness period appears to play the role of a synchronizer; in its absence the rhythm tends to free-run. It may be stated that rhythmical melatonin secretion is responsible only for maintenance of the phagocytic level, probably via the anterior hypothalamic area and thymus, while it cannot account directly for the nocturnal increase of phagocytosis.

Animals↗
PubMedDate not supplied

Neutrophil adherence in rats submitted to light-dark alternance and to constant light.

A good amount of experimental data suggests the existence of a circadian control of the inflammatory process. It was shown that migration of neutrophils in chemotactic gradient, ingestion of particles, vascular permeability etc. are rhythmical circadian functions. Melatonin, the pineal hormone secreted during the darkness phase, has been shown to be involved in the control of inflammation. The present study aims to assess whether neutrophil adherence to nylon fibers exhibits circadian rhythmicity and also if its amplitude and/or chronostructure are altered in a constant light regimen. Wistar rats were submitted to either an artificial light-darkness 12/12 regimen (LD) or to constant light (LL), for 15 days. Adherence of the neutrophils in whole blood was assessed at 10:00, 16:00, 22:00, and 04:00 hrs. In LD. neutrophil adherence appears to be a rhythmic, biphasic function, with the acrophase at 10:00, a secondary peak at 22:00 and trough values in the late dark hours. Constant light induces a depression of the adherence ability by about 10%, except for the 04:00 hrs point, where the value in LL is higher than in LD. The fact that adherence and phagocytic activity do not oscillate in phase suggests that the physiological relevance of neutrophil adherence goes beyond that of a first stage of the phagocytic process.

Animals↗
PubMedDate not supplied

A metaanalysis of certain erythropoietin characteristics established before recombinant EPO was obtained.

Beginning with 1975, our group has performed some studies using an erythropoietin (EPO ) extract prepared according to an original technique from sera of anemic rabbits. Our results have contributed to the understanding of the glycoproteinic nature of this extract as well as of some of its biological features. These results were confirmed only after 1985, when recombinant EPO was obtained. The aim of this study is to emphasize some of our priorities, controversial at that time. We have shown the radioprotective effect of an EPO extract, in correlation with red cell proliferation and with an increased rate of nucleic acid metabolism and bone marrow blood flow. Consequently, we proposed the investigation of the bone marrow function using EPO. Our results are correlated with recent data obtained with recombinant EPO. They refer to the ability of EPO to prevent apoptosis, its antioxidant effects, and its ability to modulate the sympathoadrenal response to hypoxia.

Animals↗
PubMedDate not supplied

Erythropoietin binding to the red cell membranes.

Some characteristics of Epo binding to the red cell membranes were investigated in a system in which the hormone was added to a suspension of cells in a mixture of normal serum phosphate buffered saline (1:7 (V/V)), testing the unbound Epo. Epo binding shows a gradual decrease during the maturation of red cells (0.15 U/ml packed erythrocytes, 0.285 U/ml reticulocytes and 0.375 U/ml erythroblasts from a total of 1.4 U/ml). The binding is also time- and pH-dependent. The amounts of Epo bound within 60 min are independent of temperature, but after 120 min a dissociation of the hormone-receptor complex occurred at 23 and 37 degrees; at 4 degrees C the binding continue, although at a very low rate. RBC membranes bound the hormone at pH 7.8-8 and release it at pH 6.5. The "in vivo" stimulation of beta receptors with isoproterenol increases the erythropoietic response caused by Epo, suggesting a possible relation with the adenylcyclase system.

Anemia↗