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C Tejero

Publications and source records attributed to C Tejero.

At least 37 records · Page 2Linked to original sources
PubMed1990

Thermic and pH modulation of phosphofructokinase during trout (Salmo gairdneri R.) haemopoiesis: influence of fructose 6-phosphate.

Thermic and pH modulation of phosphofructokinase (EC 2.7.1.11) activity with respect to fructose 6-phosphate has been studied comparatively in trout (Salmo gairdneri R.) haemopoietic cells and erythrocytes. Phosphofructokinase of both cellular populations displays a biphasic kinetic behaviour with respect to fructose 6-phosphate at two values of pH and temperature. In haemopoietic cells, when pH decreases the enzyme-substrate affinity increase while an opposite effect is found in erythrocytes. Decreases in temperature act as a positive modulator in haemopoietic cells while in erythrocytes this effect is observed only at low fructose 6-phosphate concentrations. Therefore a different pH and temperature modulation of phosphofructokinase during trout haemopoiesis has been established.

Animals↗
PubMed1990

Phosphofructokinase during haemopoiesis of the rainbow trout ("Salmo gairdneri R."): its isoenzymatic forms.

Phosphofructokinase (EC 2.7.1.11) from trout haemopoietic cells and erythrocytes exhibits biphasic behaviour, with respect to fructose 6-phosphate and MgATP in extracts filtered through Sephadex G-25. Two different values of Hill coefficient and S0.5 have been found for each cellular population. Two forms of the enzyme with high and low affinity for the substrates, were obtained after affinity chromatography in each cellular population. The kinetic behaviour of these forms is different and may be due to a distinct composition and/or proportion and contribution of phosphofructokinase isoenzymes in both types of cells.

Adenosine Triphosphate↗
PubMed1990

Production of humoral factors that stimulate spleen colony-forming units in mice irradiated with moderate doses of X rays.

The production of humoral factors that stimulate spleen colony-forming units (CFU-S) has been studied in irradiated mice using an in vivo diffusion chamber assay. The experiments show that a significant release of factors that stimulate CFU-S takes place in the first few days after irradiation with moderate doses of 1.5 or 5 Gy. In contrast, the release of significant amounts of these humoral factors was not seen in animals irradiated with either low (0.75 Gy) or high (10 Gy) doses of X rays. The correlation observed between the production of factors that stimulate the CFU-S and the hemopoietic regeneration kinetics of the irradiated mice suggests that these factors represent part of the physiological regulators controlling the proliferation of CFU-S.

Animals↗
PubMed1989

Pyruvate kinase during in vitro differentiation of GM-CFC haemopoietic precursor in mice: modulation by L-alanine and L-phenylalanine.

Pyruvate kinase modulation by L-alanine and L-phenylalanine was studied in cells obtained from in vitro culture of GM-CFC at different stages of development. L-Alanine and L-phenylalanine exhibit different inhibition behaviour at both differentiation stages and at various PEP concentration ranges. Therefore, a change in PK expression during granulocyte-macrophage development is suggested.

Alanine↗
PubMed1988

Persistent dose-dependent increases in cycling of haemopoietic precursor cells after irradiation.

Between 3 weeks and 36 months after irradiation of mice, there was a dose-dependent increased level of cycling in haemopoietic stem cells (CFU-S) and in granulocyte-macrophage precursor cells (GM-CFC). For CFU-S the percentage kill measured using the thymidine suicide technique increased from about 10% in controls to a high and persistent average level of about 45% after 10 Gy gamma-rays, and for GM-CFC the increase was from about 30% to about 50%.

Animals↗
PubMed1988

Long-term haemopoietic injury in mice after repeated irradiation: precursor-cell cycling and its regulation.

The cycling rate of haemopoietic stem cells (day 9 CFU-S) and granulocyte-macrophage colony forming cells (GM-CFC) in mouse femora was, in response to reduced numbers, elevated at all times of sampling between 3 weeks and 10 months after 4 repeated doses of 4.5 Gy X-rays (3 wk between doses). The level of a stimulator of CFU-S cycling was also elevated, and this was observed in both axial and marginal regions of the marrow inside the shaft. However, the rate of production of the stimulator was low; lower than previously reported in marrow regenerating after a single dose of 4.5 Gy, indicating damage to the regulatory stromal cells. The distribution of CFU-S across the axial and marginal zones of femoral marrow was changed from that in normal mice, where higher concentrations were found near the bone surface, to a more uniform distribution.

Animals↗
PubMed1987

In vitro and in vivo production of CFU-S-stimulating activities after 5-Gy total body irradiation.

In vitro and in vivo production of CFU-S-stimulating activities have been described after 5-Gy irradiation of mice using a diffusion chamber-incubation technique. The experimental results showed that bone marrow obtained 15 min after 5 Gy total body irradiation did not present detectable CFU-S stimulating activity, but was able to produce such activity in vitro within 20 h. Once the activity had been produced, 2.5 h was enough to stimulate the proliferation of CFU-S. When CFU-S were incubated for 20 h in the peritoneal cavities of mice that had been irradiated with 5 Gy immediately prior to the insertion of the chambers, or five days earlier, a marked stimulation of CFU-S turnover was observed, demonstrating the in vivo production of some humoral activity capable of stimulating CFU-S.

Animals↗
PubMed1984

The cellular specificity of haemopoietic stem cell proliferation regulators.

The range of specificity of the CFU-S proliferation inhibitor and stimulator which are produced endogenously in the bone marrow has been investigated by measuring their effects on the proportion of cells killed by tritiated thymidine in mixed colony- (CFC-mix), erythroid burst- (BFU-E) and granulocyte/macrophage colony- (GM-CFC) forming cells as well as spleen colony forming units (CFU-S). Both CFU-S and CFC-mix were triggered by the stimulator into DNA-synthesis but BFU-E and GM-CFC were unaffected. The range of activity of the inhibitor was confined solely to the CFU-S population. This defined the specificity of both inhibitor and stimulator for the multipotent cells. The differential sensitivity of CFU-S and CFC-mix to the inhibitor and the lack of it for the stimulator suggested (a) that the CFC-mix is a relatively mature subpopulation of the CFU-S compartment and (b) that the relative sensitivity of a CFU-S to these factors changes as it matures from the early stem cell stage (Inhibitor-sensitive) to the more mature stages (Stimulator-sensitive) before becoming committed to a specific line of differentiation. The specificity of the inhibitor for haemopoietic stem cells suggests its potential value during chemotherapeutic procedures.

Animals↗
PubMed1983

Some comparative properties of pyruvate kinase in haematopoietic cells and erythrocytes from rainbow trout (Salmo gairdneri R).

1. Temperature acts as a pyruvate kinase regulator in haematopoietic cells and erythrocytes. 2. Fructose-1,6-biphosphate and alanine act as allosteric modulators of pyruvate kinase in haematopoietic cells, while in erythrocytes although fructose-1,6-biphosphate exerts also allosteric effect, alanine appears to be a competitive inhibitor. ATP (1.0 mM) does not exert any clear effect on pyruvate kinase of both cellular populations. 3. The level of specific activity of pyruvate kinase in haematopoietic cells is 40-fold that of PK from erythrocytes.

Adenosine Triphosphate↗
PubMed1983

Bisphosphoglycerate synthase activity in cells of the erythrocytic line of rat.

The specific activity of bisphosphoglycerate synthase (EC 2.7.5.4) is significantly higher in rat mature erythrocytes than in reticulocytes from phenylhydrazine treated animals, while 2,3-bisphosphoglycerate levels do not differ between them. The enzyme specific activity and the concentration of 2,3-bisphosphoglycerate are both negligible in the erythroid cell pool from the bone marrow of anaemic animals. Thus, a cellular specialization in the last stages of erythropoiesis is confirmed. Human bisphosphoglycerate synthase shows a lower specific activity than that of rat without a parallel decrease in 2,3-bisphosphoglycerate levels.

2,3-Diphosphoglycerate↗
PubMed1982

[Separation of cells of the erythrocyte series of birds and mammals by distribution in biphasic polyethylene glycol-dextran systems].

Experimental conditions for the partition, in dextran (Dx) polyethylene glycol (PEG) biphasic systems, of circulating red cells, reticulocytes and bone marrow cells from adult rats, as well as of erythrocytes from chicken embryos, young animals and adult chickens, have been studied. Once the partition coefficient (K) has been calculated under optimal experimental conditions, a counter-current distribution (CCD) apparatus has been used for the separation of cells in those populations, and the influence of different factors on the distribution of cells has been analyzed. An increase in the distribution efficiency of heterogeneous cells (those from the chicken and bone marrow of rats) is achieved by increasing the sedimentation time during the CCD procedure. The position of cells (previously labelled with 59Fe) along the rotor of the CCD apparatus is related to cells age, and thus allowed us to apply the CCD procedure for the assay of some enzyme activities in the separated cells.

Animals↗
PubMed1982

[Glycolytic regulatory enzymes in erythrocytes, reticulocytes and immature bone marrow cells of rats].

Kinetic characteristics of glycolytic kinases in cells of the erythrocytic line have been studied in rats. Erythrocyte Hexokinase (HK) shows low Km, while in reticulocytes a high Km enzyme is also found. The low Km HK is inhibited by higher than physiological concentrations of 2,3-bisphosphoglycerate. The ATP inhibition of 6-phosphofructokinase (PFK) from erythrocytes and reticulocytes, and the deinhibitory effect shown by AMP and cyclic-AMP, are lower in situ than in vitro. The sigmoidal fructose-6-phosphate saturation curve for PFK is observed in vitro but not in situ. Under this approach the enzyme shows hyperbolic kinetics, lower response to positive allosteric effectors and a decrease in activity. An antagonistic effect is shown by cyclic-AMP and cyclic-GMP on the in vitro sigmoidal behaviour of PFK. Phosphoglycerate kinase (PGK) is an hyperbolic enzyme, with similar Km values, in erythrocytes, reticulocytes and bone marrow cells. Pyruvate kinase shows sigmoidal kinetics and activation by fructose-1,6-bisphosphate (FBP) in erythrocytes; a non rectangular hyperbolic kinetics with negative cooperativity, lack of response to FBP and inhibition by ATP and L-alanine, was observed in the bone marrow enzyme.

Animals↗
PubMed1982

[Metabolism of the organic phosphate regulators of oxygenation in cells of the erythrocyte series in birds and mammals].

In mammals, bisphosphoglycerate-synthase activity, whose assay methods are previously discussed, increases gradually along erythropoiesis, leading to a consequent enhancement of 2,3-bisphosphoglycerate formation. Avian erythrocytes, on the other hand, contain inositol-pentaphosphate as major organic phosphate starting from egg eclosion, which substitutes embrionary ATP and 2,3-BPG in the regulatory function. The IHP of phytase and the disappearance of 2,3-BPG synthesis, also inhibitor of enzyme activity, should be considered responsible for IPP accumulation.

2,3-Diphosphoglycerate↗
PubMed1981

Separation by counter-current distribution of rat and chicken erythrocytes of different age, and its application to the assay of enzyme activities.

The separation of cells with different ages from erythrocyte populations of adult rats and young or adult chickens have been achieved by counter-current distribution (CCD). A thin-layer CCD apparatus has been employed. Erythrocytes from blood samples taken at different times after 59Fe i.p. injection were separated by CCD. By compilation in a "composite curve" of the hemoglobin and radioactivity CCD profiles obtained for each erythrocyte population, the distribution of cells according to age can be inferred. Young erythrocytes of rats are located at the right part of the CCD curves, while older cells are distributed towards the left. An opposite distribution has been found for erythrocytes from adult or young chickens. As a first attempt for the application of the CCD procedure to the assay of enzyme activities, it was found a decrease in phytase activity as the age of chicken erythrocytes increases and an increase in phosphoglycerate kinase and phosphofructokinase as the age of rat erythrocytes increases.

6-Phytase↗
PubMed1977

Comparative activation by AMP and cyclic-AMP of rat erythrocyte and reticulocyte glycolysis.

Incubation of raty erythrocytes and reticulocytes in Tris-Ringer's medium with 5 mM cyclic-AMP or AMP increased lactate formation and glucose utilization. The glycolysis-stimulating effect of cyclic-AMP is very similar to that of AMP and, in both cases, it seems to be higher in reticulocytes than in erythrocytes. 0.5 mM norepinephrine produced a much higher lactate formation in reticulocytes than in erythrocytes, suggesting a greater adenylate cyclase activity in younger cells. 300 micrometer cyclic-AMP and AMP reverse inhibition produced by ATP (up to 1.5 micrometer) on phosphofructokinase from rat reticulocyte haemolysates. Both nucleotides are positive allosteric effectors of the enzyme as shown by displacement of F6P-saturation curve to hyperbolic kinetics. Similar results were previously obtained with rat erythrocytes. This deinhibitory effect is suggested to be responsible of the above glycolysis-stimulating effect.

Adenosine Monophosphate↗
PubMedDate not supplied

Clinical design and evaluation of the prototype of a new digital audioprosthesis for profound hearing loss: speech recognition aspects.

The design and implementation of the prototype of a digital hearing aid and its computerized fitting interface, followed by a basic preliminary clinical evaluation concerning speech recognition aspects, is reported. The final device is particularly destined to those patients suffering sensorineural hearing losses with recruitment and problems for speech recognition. The prototype is based on the digital signal processor TMS320C30. The host is a personal computer. The primary concept of the processing strategy is the 'integral treatment of acoustic information' within the remaining auditory field of the patient leading to minimum modification of the signal profile. The processing stages include linear amplification, specially designed AD conversion, real fast Fourier transform, 128 multiband single treatment (compression threshold and magnitude of compression), inverse fast Fourier transform, and DA conversion. Compression parameters and pure-tone audiometry data are entered by the computerized fitting interface which also provides real time information of input and output spectral profile. The preliminary clinical evaluation here reported corresponds to a series of 13 patients and it is focused on speech recognition performances. Ten patients had sensorineural hearing loss. Three subjects served as controls. All subjects were studied by an extensive audiological protocol. In 6 patients the prototype improved the maximum intelligibility with respect to unaided hearing reaching levels in the range of 90-100%. In 4 patients using conventional hearing aids, the prototype improved the maximum intelligibility with respect to the previous aided hearing. Values reached the same range as in the former 6 patients. Straightening of the speech audiometry curves was observed in those patients with recruitment. Two controls with previously normal speech recognition showed no worsening and others with conductive deafness reported additional improvement of the responses in noisy conditions with respect to the audioprosthesis in use.

Adult↗
PubMedDate not supplied

[Symptomatic epilepsy: review of 208 patients].

OBJECTIVE: To determine the main etiological mechanisms of symptomatic epilepsy and its frequency according to age. PATIENTS AND METHODS: We made a retrospective analysis of 208 patients admitted during a period of four and a half years, studying the variables: age, sex and type of seizures: simple partial, secondarily generalized partial, complex partial, tonic-clonic, generalized tonic, and also EEG and neuroimaging. RESULTS: The main etiological mechanisms found were: vascular (31.25%), alcoholic (12.01%), intracranial disorders (9.61%), traumatic (5.28%), degenerative (5.28%), infectious (2.88%) and cryptogenic (33.65%). In the last group there was an outstandingly large proportion of patients with silent infarcts. When considering vascular epilepsy, those seizures occurring during the acute phase of the stroke (24/65) are differentiated from those of late onset (41/65). In the latter there was a marked predominance of ischemic etiology (48.78% corresponded to extensive infarcts in the territory of the middle cerebral artery; 36.58% were associated with partial infarcts) probably because of the greater frequency of ischemic stroke as compared with hemorrhagic stroke. After the acute phase, the latency was of 10.68 +/- 0.43 months and the most frequent seizures were tonic-clonic (48.78%). CONCLUSION: In persons under 30 years of age, etiology is multifactorial; between 30 and 50 years of age alcoholic epilepsy (39.53%) and traumatic epilepsy (11.62%) predominate; over the age of 50 years the cause was vascular in 43.5%. In the latter age group there was a high proportion of patients with heraldic seizures.

Acute Disease↗