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L Quevedo

Publications and source records attributed to L Quevedo.

At least 19 recordsLinked to original sources
PubMed2001

Some particularities of sodium nitroprusside stimulatory effects on food intake.

It was previously shown that sodium nitroprusside (NP) stimulates food (FI) and water (WI) intakes when injected intraperitoneally (i.p.) in male rats deprived for 1-h of both food and water during day time. The present work shows that: 1) intramuscular NP increased only water intake; 2) when NP was i.p. injected simultaneously without 1-h deprivation it slightly reduced both intakes in the first 30 min but stimulated significantly FI between 30 and 60 min, and 3) it increased significantly FI even in absence of available water, while WI in absence of food was practically not affected. In conclusion NP effect on FI does originate mainly in the splanchnic area, it requires a latency of about 30 min, and stimulation of FI by NP triggers an increase in WI and not the other way around.

Animals↗
PubMed1998

Effect of intraperitoneal nitroprusside and adrenergic agonists on food and water intake.

In previous works it was shown that catecholamine-induced hypodipsia is mediated by alpha1-adrenergic receptors while food intake (FI) inhibition supposes also beta-adrenergic participation. We used sodium nitroprusside (N) as a vasodilator, alone or mixed with various adrenergic agonists and measured FI and water intake (WI) in rats either deprived food and water overnight or in postprandial conditions after only 1 hour of deprivation in day time. N injected alone had no effect after overnight deprivation but diminished significantly norepinephrine (NE)-induced inhibition of both intakes, while epinephrine (E) inhibited only FI. In day time, N stimulated 30 min FI by 60% and WI by 84% in male but not in female rats. Isoproterenol (I) stimulated only WI (by 155%), while phenylephrine (P) and E inhibited it by 55%. In the presence of N, I increased WI even more (by 220%) but reduced FI. P + N and E + N increased FI by 41% and 128% as compared with P and E, respectively. Only P-induced inhibition of WI was canceled in presence of N. The results show that N, probably due to nitric oxide production, may induce hyperphagia and hyperdipsia in 1 hour-deprived male rats and also that catecholamine effects on FI and WI are differently modulated by N.

Adrenergic Agonists↗
PubMed1998

Cu2+ ions interact with cell membranes.

The influence of Cu2+ ions on the physical properties of resealed human erythrocyte membranes was studied by fluorescence spectroscopy. A net ordering effect was observed at the hydrophobic-hydrophilic interface both in the bulk as well as in the lipid-protein boundary. The explanation for this result was found by X-ray diffraction performed in multilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. Cu2+ did not significantly affect the structure of DMPE; however, DMPC polar head and hydrocarbon chain arrangements were perturbed at low but reordered at high Cu2+ concentrations. These effects were respectively explained in terms of a limited and extended interaction between Cu2+ ions and DMPC PO4 groups. Thus, the ordering effect in the erythrocyte membrane could be based on the interaction of this cation with phosphatidylcholine phosphate groups located in its outer leaflet. This binding, besides producing a decrease of membrane fluidity, might also induce a change in its electric field. These two effects should affect the activity of membrane proteins, particularly of ion channels. In fact, it was found that increasing concentrations of Cu2+ ions applied to either the mucosal or serosal surface of the isolated toad skin elicited a dose-dependent decrease of the short-circuit current (SCC) and of the potential difference (PD). These results lead to the conclusion that Cu2+ ions inhibited Na+ transport across the epithelial cell membranes.

Animals↗
PubMed1998

The organochlorine herbicide chloridazon interacts with cell membranes.

Chloridazon is a widely used organochlorine herbicide. In order to evaluate its perturbing effect on cell membranes it was made to interact with human erythrocytes, frog adrenergic neuroepithelial synapse and molecular models. These consisted in multilayers of dimyristoylphosphatidylethanolamine (DMPE) and of dimyristoylphosphatidyltidylcholine (DMPC), representative of phospholipid classes located in the inner and outer monolayers of the erythrocyte membrane, respectively. X-ray diffraction showed that chloridazon interacted preferentially with DMPC multilayers. Scanning electron microscopy revealed that 0.1 mM chloridazon induced erythrocyte crenation. According to the bilayer couple hypothesis, this is due to the preferential insertion of chloridazon in the phosphatidylcholine-rich external moiety of the red cell membrane. Electrophysiological measurements showed that nerve stimulation was followed immediately by a transient increase in short-circuit current (SCC) and in the potential difference (PD) of the neuroepithelial synapse. Increasing concentrations of chloridazon caused a dose-dependent and reversible decrease of the responses of both parameters to 76% of their control values. The pesticide induced a similar (28%) significant time-dependent decrease in the basal values of the SCC and of PD. These results are in accordance with a perturbing effect of chloridazon on the phospholipid moiety of the nerve fibre membrane leading to interference with total ion transport across the nerve skin junction.

Animals↗
PubMed1998

[Clinical characterization of patients with multiple sclerosis defined in Cuba].

INTRODUCTION: Since 1975 no studies have been done in Cuba defining the clinical characteristics of patients with multiple sclerosis (MS). OBJECTIVE: To describe the characteristics of a group of Cuban patients with definite clinical MS. MATERIAL AND METHODS: Fifty eight patients with definite clinical MS were studied (Poser et al) with normal motor (VCM) and sensory (VCS) conduction velocities. Tests were done on them: clinical scale (Scripps), incapacity (EDSS) and quality of life (Steps), together with various complementary tests. Each patient was classified according to the way in which the disease evolved. Also the two commonest clinical types were compared and we applied the difference test between percentages of non-paired samples with an alfa level of 0.05. RESULTS: Onset of the illness in most cases was before the age of 40 (86.1%), 75.9% were women and 82.8% were white. In 15.3% there was a family history of MS. In 25.9% there were psychiatric disorders and trigger factors (43.1%. The most frequent initial symptoms were pyramidal (48.3%) sensorial (41.4%) and cerebellar (39.7%). Scripps scale scores were < 80 in 60.2%, in EDSS < 5 (61.9%) and in the Clinical Steps < 3 in 65.4%). Motor potentials (81.9%) somatosensory potential (PESS) (72.3%) and magnetic resonance imaging (MR) (76.4%) were the most abnormal results. Exacerbation-remission (ER) was the most frequent type of evolution (53.4%) generally affecting patients aged under 40 years old (p = 0.02), EDSS < 5 (64.4%), Scripps > 80 (61.2%), Steps < 3 (95.6%), pyramidal system involvement (58.5%), cerebellar (29.2%) and MRI abnormality (80%). The progressive primary form (PP) was the second most frequent (29.3%); 29.4% were under 40 years of age, had more marked changes in all functional system (100%), degree of incapacity and quality of life (100%). PESS (92.5%); the urodynamic tests 58.85%) were less positive on MRI (54.5%) as compared with the ER form. CONCLUSIONS: The differences found between the clinical forms ER and II indicate that there is greater deterioration in the PP form, probably due to age and more cerebellar and spinal cord involvement.

Adolescent↗
PubMed1995

Norepinephrine inhibition of water and food intake: comparison with vasopressin effects.

UNLABELLED: In a previous publication we showed that intraperitoneally (IP) injected norepinephrine (NE) induces hypodipsia (hD) in rats by an alpha 1-adrenergic effect which might be due to splanchnic vasoconstriction. In the present work we administered two vasoconstrictive hormones: NE 250 ug/kg and arginine vasopressin (VP) 550 mU/kg either by IP or intramuscular (IM) route to fasted rats in two different thirst-inducing conditions: (a) water-deprivation; or (b) induced hyperosmolarity. IP NE inhibited significantly food and water intake under both conditions. IM NE did not affect food intake and elicited significantly less hD and this only in (a). VP did not affect food intake but induced hD regardless of the route of administration in (a) but not in (b). NE administrated to anesthetized rats after food and water deprivation increased arterial pressure by both routes while VP effect was weaker and more variable. IN CONCLUSION: blood pressure elevation may be implicated in the hD effect but IP NE elicits a specific splanchnic action; splanchnic-induced hypophagia is not necessarily related to water intake inhibition.

Animals↗
PubMed1995

Potentiation of the immobility response elicited by bandaging and clamping in mesencephalic rats.

In earlier work, we showed that adult rats exhibit immobility response (IR) if a clamp is fastened to the skin of the nape of the neck, but not at other areas of the body, and not by bandaging. The present study characterizes IR in adult rats with complete mesencephalic transections. In the mesencephalic rats, the duration of the IR not only increased, but the stimuli capable of eliciting it were more diverse. All head and body areas clamped or bandaged were capable of inducing a profound IR. In contrast, the IR in intact rats was of shorter duration, and was only induced by clamping the neck, or by bandaging the upper or the lower torso. Furthermore, unlike the mesencephalic rats the ability of the bandaging to induce IR is reduced after the first trial and finally disappears. Only clamping the neck was able to persistently induce IR in intact rats. These data support the hypothesis that the IR control system is in the midbrain, hindbrain or spinal cord, and that systems above the mesencephalon modulate the IR. Such modulation appears to involve the ability to discriminate amongst tactile stimuli, and to integrate previous experience.

Animals↗
PubMed1995

Inhibitory action of hydrogen peroxide on a high-resistance epithelium.

The present study describes the action of H2O2 on active transporting epithelium, and the partial blockade of this action by antioxidants. The addition of increasing concentrations of H2O2 (0.80; 8.0 and 24.0 mmol/l) to the mucosal surface of isolated toad skin causes an irreversible and dose-dependent inhibition of the short circuit current (SCC) and potential difference (PD). Quantitative determination of the parameters of the electrical equivalent circuit of the skin, by means of Isaacson's amiloride test, shows that the most affected parameters were the SCC, PD and shunt conductance. When the skins were preincubated with mannitol and vitamin E, the inhibition elicited by H2O2 was partially blocked; on the other hand, when the skins were preincubated with superoxide dismutase or allopurinol, this inhibition remains unchanged. The thiobarbituric acid method was used as an indirect quantification of lipid peroxidation. The inhibitory action of H2O2 in terms of the equivalent electrical circuit and the parallel production of lipid peroxidation points to free-radical formation. Furthermore, the significant blockade of this action by some enzymatic antioxidants is in agreement with this hypothesis.

Allopurinol↗
PubMed1993

Pentachlorophenol (PCP) inhibits ion transport in the isolated toad cornea.

1. Active chloride transport from the stroma to the epithelial surface (tear side) accounts for 80% of the amphibian cornea short-circuit current (SCC). 2. The effect of pentachlorophenol (PCP, a wood preservative) on the bioelectric parameters of the toad Caudiverbera caudiverbera isolated cornea was studied. 3. PCP applied to the epithelial surface in the concentration range 0.3-4.3 microM caused a dose-dependent inhibition of the PD and of the SCC in 7 corneas. This inhibition was irreversible at all concentrations after several washouts. The agent had no effect when applied to the endothelial surface. 4. In 4 experiments the inhibitory effect was partly reversed by the addition of 1 microM calcium ionophore A-23187 to the epithelial surface. 5. It is concluded that PCP is an inhibitor of corneal active chloride transport and that this structure shows greater sensitivity to this agent than other tissues.

Animals↗
PubMed1992

Inhibition of the sodium transport by pentachlorophenol (PCP) in toad skin (Pleurodema thaul).

1. The effects of pentachlorophenol (PCP) were studied in vitro on an active ionic transporting epithelium. Ussing's technique was applied on the isolated Pleurodema thaul skin. 2. Concentrations of PCP in the range 0.003-0.043 mM caused an irreversible dose-dependent inhibition in both the short-circuit current and the potential difference. 3. Parameters of an electrical equivalent circuit were calculated applying the Isaacon's amiloride test. 4. It was also shown that PCP produced a significant increase in the O2 consumption of the skin. 5. The inhibitory action of PCP on active sodium transport in terms of the equivalent electrical circuit and the increased oxygen consumption points to an uncoupling action of PCP on the oxidative phosphorylation.

Animals↗
PubMed1990

The effects of pentachlorophenol (PCP) at the toad neuromuscular junction.

1. Effects of PCP at the frog neuromuscular junction were studied in vitro in sciatic nerve sartorius muscle of the toad Pleurodema-thaul. 2. Within the concentration 0.003-0.1 mM, PCP caused a dose-time-dependent block of evoked transmitter release acompanied by an increase in the rate of spontaneous quantal release. 3. PCP induced an increase in miniature endplate potential (MEPP) frequency and it was not antagonized in a Ca2(+)-free medium, indicating that it does not depend upon Ca2+ influx from the external medium, but may act by releasing Ca2+ from intraterminal stores. 4. The present data, together with previous results concerning PCP at eighth sympathetic ganglia indicate that 3,4-diaminopyridine (3,4-DAP) counteracts the effects of PCP on synaptic transmission. This result suggests that PCP interfering Ca2+ influx occurs during depolarization of motor nerve terminals.

4-Aminopyridine↗
PubMed1990

The action of progesterone on sodium transport of isolated toad skin. Further evidences of a metabolic action.

To understand the mechanism of progesterone inhibition of the sodium influx in the toad skin, the effects of the hormone on the active sodium transport and oxidative metabolism of the transporting cells were examined. A direct relationship was observed between the initial value of the short circuit current and the sensitivity of a given skin toad preparation to progesterone. Progesterone had a higher effect on the sodium potential than on any other parameter of an equivalent electrical circuit of toad skin. Direct measurement of oxygen consumption indicated that progesterone can act as a blocking agent of the respiratory chain of the sodium transporting cells of toad skin.

Animals↗
PubMed1988

[AIDS and the dentist].

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Acquired Immunodeficiency Syndrome↗