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Biomedical subjects

M C Nicolau

Publications and source records attributed to M C Nicolau.

13 recordsLinked to original sources
PubMed1999

Interhemispheric differences in awake and sleep human EEG: a comparison between non-linear and spectral measures.

Interhemispheric differences in the EEG of nine healthy right-handed human subjects (C3 vs. C4 derivations) were investigated during resting wake with closed eyes (CE) and sleep stages I, II, III, IV and REM. The harmonic power spectral density within the EEG main spectral bands, the fractal (Dr) and the correlation (D2) dimension as well as the largest Lyapunov exponent (lambda1) of both hemispheres were compared. In addition, the relationships between non-linear and spectral measures were analyzed. Dr, D2, lambda1 and the power in alpha band exhibited interhemispheric differences during waking, the values from the right hemisphere (RH) being higher than those of the left (LH) except for lambda1. During slow wave sleep (SWS), non-linear parameters detected opposite EEG asymmetries (D2 in stage III and lambda1 in stage IV) to those found in the other behavioural stages. In addition, both D2 and lambda1 were correlated (negatively) with the power in the delta band, but lambda1 was also correlated (positively) with the power in the alpha and beta bands. In conclusion, RH appears to be more complex though more predictable than the LH during CE and sleep stages I and II, these characteristics changing to the LH during SWS.

Alpha Rhythm↗
PubMed1999

Nonlinear, fractal, and spectral analysis of the EEG of lizard, Gallotia galloti.

Electroencephalogram (EEG) from dorsal cortex of lizard Gallotia galloti was analyzed at different temperatures to test the presence of fractal or nonlinear structure during open (OE) and closed eyes (CE), with the aim of comparing these results with those reported for human slow-wave sleep (SWS). Two nonlinear parameters characterizing EEG complexity [correlation dimension (D2)] and predictability [largest Lyapunov exponent (lambda(1))] were calculated, and EEG spectrum and fractal exponent beta were determined via coarse graining spectral analysis. At 25 degrees C, evidence of nonlinear structure was obtained by the surrogate data test, with EEG phase space structure suggesting the presence of deterministic chaos (D2 approximately 6, lambda(1) approximately 1. 5). Both nonlinear parameters were greater in OE than in CE and for the right hemisphere in both situations. At 35 degrees C the evidence of nonlinearity was not conclusive and differences between states disappeared, whereas interhemispheric differences remained for lambda(1). Harmonic power always increased with temperature within the band 8-30 Hz, but only with OE within the band 0.3-7.5 Hz. Qualitative similarities found between lizard and human SWS EEG support the hypothesis that reptilian waking could evolve into mammalian SWS.

Animals↗
PubMed1997

Main trends in rectal temperature during sleep. Hypnogram and thermogram.

Changes in sleep state and night-time body temperature were studied in 13 healthy young men. Temperature data showed serial dependence that was removed when considering three main segments of the thermogram: an initial rapid drop between 60 and 140 min after lights off, followed by a slower decrease to the thermal minimum and a final temperature increase until waking. The first segment was fitted by a two-term function, while the other two segments were fitted by linear regression. Temperature data obtained after fitting these models were stationary and used to calculate the fast Fourier transformation and the cross-correlation functions between the hypnogram and the thermogram of each subject. Attaining stationarity has unmasked short oscillations during sleep and some temperature series showed the presence of ultradian oscillations with a period of 90-100 min. Significant cross-correlations between sleep stages and body temperature were found, and the parameters of the two-term function fitted to the first temperature drop were related to the sign of the correlation and to that time series (sleep or temperature) which preceded the other during the night.

Adult↗
PubMed1993

Histaminergic drugs in the rat caudate nucleus: effects on learned helplessness.

The effect of pharmacological manipulation of histaminergic receptors in the caudate nucleus (CN) has been examined in rats previously submitted to inescapable electric shock to produce learned helplessness (LH). Histamine H1 agonist 2-tiazolylethyl amine (TEA) microinjection produced protective effects, preventing the activity and cognitive loss typical in LH. Injection of the H1 antagonist astemizole (AZ) produced effects symmetrical to those produced by TEA, further reducing activity and impairing cognitive functions. The histamine H2 agonist 4-methyl-histamine (4MH) produced a shift on the side preference for rotation that interfered in the learning tests and obscured the effects of this drug on LH. Injection of the H2 antagonist cymetidine (CYM) caused LH-like effects in control animals. Thus, brain histamine seems to play a relevant role in the control of motor and cognitive functions of the CN.

Animals↗
PubMed1993

On the evolution of waking and sleeping.

1. The aim of this paper is to present a new hypothesis to explain the evolution of the sleeping and waking states. 2. We propose that the reptilian waking state and the mammalian slow wave sleep are homologous states. 3. We also propose that instead of looking at the polygraphic sleep as a new evolutive acquisition of mammals and birds, it seems more convenient to look at the full waking state; the "advanced wakefulness" as the true new evolutionary acquisition of these animals. 4. These conclusions are reached after examining some available reports of slow wave electroencephalogram in waking reptiles, some other reports showing signs of rapid eye movement sleep in this same group and the coevolution between sleep states and thermoregulation. Finally, a clear parallelism between sleep ontogeny and phylogeny is shown under the light of the proposed hypothesis.

Aging↗
PubMed1992

Morphofunctional changes in gastrointestinal tract of rats due to cafeteria diet.

Female rats fed a cafeteria diet from birth developed obesity at 60 days of age and their stomach, small intestine and caecum were enlarged when compared with controls, i.e. these regions had greater food storage capacity. In spite of the enlargement, these regions had similar or reduced weight and linear density, which is seen as proof of reduced mechanical performances. Cafeteria diet produced increased glucose duodenal absorption in older animals unlike the typical reduction known in controls. Tryptophan absorption was maintained high in adulthood, compensating for the low structural nutritive properties of the cafeteria diet. The results are interpreted as an adaptation to the cafeteria diet effects and properties: the characteristic overeating of foodstuffs with greater energy density, lower mechanical requirements and lower structural nutritive value than pelleted chow.

Adaptation, Physiological↗
PubMed1986

[Effect of intracerebroventricular injection of histamine on the behavior of the white rat].

Previous references showed that the histamine injected peripherically produced a deterioration of the learning in experimental animals. The effects of 100 and 200 micrograms of histamine administered in the cerebral lateral ventricle, have been tested using an experimental paradigm which isolated attentional, motivational, and motor factor from the complex learned behavior. The obtained results showed to be similar to those produced by peripheric injection, and demonstrated a worsening in attentional, motivational, and motor parameters.

Animals↗
PubMedDate not supplied

A simple thin-layer chromatographic method for the analysis of buprenorphine in urine.

A simple and sensitive (at the ng/mL level) method for buprenorphine assay in urine is described. Buprenorphine is extracted by a C18 cartridge, derivatized with dansyl chloride, resolved by a uni-dimensional, two developing mobile phase high-performance thin layer chromatography system and quantified by fluorescence densitometry at 340 nm.

Analgesics, Opioid↗
PubMedDate not supplied

A simple method for plasma cannabinoid separation and quantification.

A sensitive (up to nanogram level) method for resolving a cannabinoid mixture in plasma is described. Cannabinoids were extracted with a C-18 Sep Pak cartridge and derivatized with dansylchloride. Then the derivatives were resolved on thin layer HPTLC silica plates which were developed and quantified by fluorescence densitometry at 340 nm.

Cannabinoids↗
PubMedDate not supplied

Thin-layer chromatographic determination of brain catecholamines and 5-hydroxytryptamine.

A simple and sensitive (up to nanogram level) method to determine norepinephrine, serotonin and dopamine in rat brain is described. The amines are acetylated and the derivatives are resolved by thin layer chromatography (TLC) on silica high performance thin layer chromatography (HPLC) plates. Quantification is achieved by fluorescence densitometry at 415 nm excitation wavelength.

Animals↗
PubMedDate not supplied

Thin-layer chromatographic determination of catecholamines, 5-hydroxytryptamine, and their metabolites in biological samples: a review.

A review of methodology for separation, detection, and quantitative determination of catecholamines, 5-hydroxytryptamine, and their acidic metabolites in biological tissue and fluids by thin-layer chromatography is presented. Selected procedures, including fluorometric scanning densitometry for catecholamine acetyl derivatives and color scanning densitometry for acids, are described.

Biogenic Amines↗