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Biomedical subjects

L M Vera

Publications and source records attributed to L M Vera.

8 recordsLinked to original sources
PubMed2006

Feeding entrainment of locomotor activity rhythms, digestive enzymes and neuroendocrine factors in goldfish.

The existence of food anticipatory activity (FAA) in animals subjected to daily feeding schedules seems to be mediated by a feeding-entrainable oscillator (FEO). Such an FEO may help in anticipating meal time and so optimizing food acquisition and nutrient utilization. In this study we investigated the existence of FAA and whether digestive enzymes, plasma cortisol, hypothalamic NPY and gastrointestinal tract (GIT) and plasma melatonin were entrained by periodic feeding in goldfish. We observed that periodically fed goldfish showed FAA in locomotor activity as well as in amylase and NPY. Alkaline protease and GIT melatonin were higher after feeding, whereas plasma cortisol levels were reduced. Plasma melatonin remained unmodified before and after meal time. These results suggested that scheduled feeding entrained both behavioral and certain physiological patterns in goldfish, FAA being of adaptive value to anticipate a meal and prepare the digestive physiology of fish.

Activity Cycles↗
PubMed2006

Locomotor, feeding and melatonin daily rhythms in sharpsnout seabream (Diplodus puntazzo).

Sharpsnout seabream is a marine teleost of increasing interest for Mediterranean aquaculture, but there is still a lack of information regarding its circadian organization. In this study, we have investigated sharpsnout seabream locomotor activity, feeding and plasma melatonin daily rhythms under a 12:12-h LD cycle, as well as the persistence of locomotor activity circadian rhythmicity under constant light (LL) conditions. When submitted to an LD cycle, most sharpsnout seabream displayed a diurnal locomotor pattern, with an average 74% of activity recorded during daytime. However, along the experiment 40% of fish spontaneously changed their locomotor rhythm phasing and became nocturnal. Feeding behaviour, nevertheless, remained strictly diurnal in all cases, with 97% of food demands being made during the light period. Free-running locomotor rhythms were recorded in one third of the fish kept under LL. Daily plasma melatonin levels displayed a rhythmic profile, with low daytime values (111 pg/ml) and high nighttime concentrations (791 pg/ml). Taken together, these results evidence a high degree of plasticity for sharpsnout seabream activity patterns, as well as phasing independence of locomotor and feeding rhythms. Finally, the existence of a well-defined daily rhythm of plasma melatonin was found.

Animals↗
PubMed2005

Independent association between inflammatory markers (C-reactive protein, interleukin-6, and TNF-alpha) and essential hypertension.

High blood pressure (HBP) has been associated with elevated C-reactive protein (CRP), a marker of chronic mild inflammation. However, the association between HBP and other inflammatory markers, particularly interleukin 6 (IL-6) and tumour necrosis alpha (TNF-alpha), has not been evaluated in well-controlled studies. We examined the cross-sectional relationship between IL-6, TNF-alpha, and CRP and HBP in a random sample of 196 healthy subjects. All markers were measured in duplicate with high-sensitivity ELISA tests. Three blood pressure (BP) measurments were averaged for the analysis, and subjects with systolic BP >or=140 and/or diastolic BP >or=90 mmHg were considered hypertensive. Log binomial regression was used to estimate multivariate-adjusted prevalence ratios (PR) of HBP. Of the subjects, 40% (79) were hypertensive (mean age: 44 years; range 30-64). After adjustment for age, sex, body mass index, family history of HBP, and the level of the other inflammatory markers, subjects in the second (PR: 3.10, P=0.003), third (PR: 2.32; P=0.031), and fourth quartiles (PR: 2.30; P=0.036) of IL-6 were more than twice as likely to be hypertensive than those in the first quartile. Corresponding PR estimates for TNF-alpha levels were 1.41 (P=0.014) for the second; 1.59 (P=0.001) for the third; and 1.61 (P=0.025) for the fourth quartile. The CRP-HBP association was not statistically significant. Our results suggest that TNF-alpha and IL-6 could be independent risk factors for HBP in apparently healthy subjects. Nevertheless, the temporal relationship between elevated inflammation markers and HBP should be ascertained in prospective cohort studies.

Adult↗
PubMed2005

Influence of light intensity on plasma melatonin and locomotor activity rhythms in tench.

Melatonin production by the pineal organ is influenced by light intensity, as has been described in most vertebrate species, in which melatonin is considered a synchronizer of circadian rhythms. In tench, strict nocturnal activity rhythms have been described, although the role of melatonin has not been clarified. In this study we investigated daily activity and melatonin rhythms under 12:12 light-dark (LD) conditions with two different light intensities (58.6 and 1091 microW/cm2), and the effect of I h broad spectrum white light pulses of different intensities (3.3, 5.3, 10.5, 1091.4 microW/cm2) applied at middarkness (MD) on nocturnal circulating melatonin. The results showed that plasma melatonin in tench under LD 12:12 and high light conditions displayed rhythmic variation, where values at MD (255.8 +/- 65.9 pg/ml) were higher than at midlight (ML) (70.7 +/- 31.9 pg/ml). Such a difference between MD and ML values was reduced in animals exposed to LD 12: 12 and low light intensity. The application of 1 h light pulses at MD lowered plasma melatonin to 111.6 +/- 3.2 pg/ml (in the 3.3-10.5 microW/cm2 range) and to 61.8 +/- 18.3 pg/ml (with the 1091.4 microW/cm2 light pulse) and totally suppressed nocturnal locomotor activity. These results show that melatonin rhythms persisted in tench exposed to low light intensity although the amplitude of the rhythm is affected. In addition, it was observed that light pulses applied at MD affected plasma melatonin content and locomotor activity. Such a low threshold suggests that the melatonin system is capable of transducing light even under dim conditions, which may be used by this nocturnal fish to synchronize to weak night light signals (e.g., moonlight cycles).

Animals↗
PubMed2004

Daily locomotor activity and melatonin rhythms in Senegal sole (Solea senegalensis).

The daily locomotor and melatonin rhythms of the Senegal sole, a benthonic species of increasing interest in aquaculture, are still unknown, despite the fact that such knowledge is of prime importance for optimising its production. The aim of the present research was therefore to investigate the daily rhythms of locomotor activity and melatonin in the Senegal sole. For this purpose, the individual locomotor activity rhythms of fish were registered using a photocell. Plasma and ocular melatonin rhythms were studied in animals reared in circular tanks placed in earth under an LD 12:12 light regime and 16-18 degrees C temperature range (spring equinox). Blood and eye samples were taken every 3 h during a complete 24-h cycle. The impact of a light pulse in the middle of the dark period (MD) on plasma melatonin was also studied. Locomotor activity was mainly nocturnal, with 84.3% of the total activity occurring during darkness. The levels of plasma melatonin were higher at night (55 pg/ml) than during the day (2 pg/ml), while ocular melatonin levels appeared to be arrhythmic. Both weight and melatonin content were found to be significantly higher in the left eye in relation to the right eye. A light pulse in MD provoked a significant decrease in plasma melatonin levels. In summary, photoperiod is a key factor in synchronizing locomotor activity and melatonin rhythms in the Senegal sole, whose nocturnal habits should be taken into account for their rearing by aquaculture.

Animals↗
PubMed2001

Is C-reactive protein an independent risk factor for essential hypertension?

CONTEXT: C-reactive protein (CRP), predicts coronary heart disease incidence in healthy subjects and has been associated with decreased endothelium-dependent relaxation, a potential risk factor for hypertension. However, the relationship between CRP and hypertension has not been studied. OBJECTIVE: To assess whether circulating levels of CRP are independently related to essential hypertension. DESIGN: Cross-sectional population survey. We measured circulating levels of CRP, blood pressure and cardiovascular risk factors among participants. Binomial regression was used to calculate the adjusted effect of CRP on the prevalence of hypertension. SETTING: General community of Bucaramanga, Colombia. PARTICIPANTS: A random sample of 300 subjects > or = 30 years old. MAIN OUTCOME MEASURE: Arterial blood pressure. RESULTS: Overall hypertension prevalence was 46.0%. The unadjusted prevalence of hypertension was 58.7% in the highest quartile of CRP, but only 34.7% in the lowest quartile. After adjustment for age, sex, body mass index, family history of hypertension, fasting glycemia, sedentary behaviour, and alcohol consumption, the prevalence of hypertension was 1.14 [95% confidence interval (CI), 0.82, 1.58; P= 0.442], 1.36 (95% CI, 0.99, 1.87; P= 0.057) and 1.56 (95% CI, 1.14, 2.13; P = 0.005) times higher in subjects in the second, third and fourth quartiles of CRP, as compared to subjects in the first quartile. CONCLUSIONS: Our results suggest, for the first time, that CRP level may be an independent risk factor for the development of hypertension. However, because of the cross-sectional nature of our study, this finding should be confirmed in prospective cohort studies, aimed at elucidating the role of CRP in the prediction, diagnosis and management of hypertension.

Aged↗
PubMed1978

[Temperature effects on the EEG and evoked potentials in Reptilia (Lacerta galloti) (author's transl)].

The effect of temperatures from 5 degrees to 40 degrees C on EEG amplitude, evoked potentials amplitudes to optical stimuli and latencies of components of evoked potential in lizard Lacerta galloti, have been studied, by means of chronically implanted electrodes in dorsal and medial telencephalic cortex. Evoked responses show with greater amplitude in the medial cortex, although latencies were closely similar for both regions.

Animals↗