Aggregation features of partially unfolded bovine serum albumin modulated by hydrogenated and fluorinated surfactants: Molecular dynamics insights and experimental approaches.

Protein aggregation plays important roles in life science as, for instance, those associated to neurodegenerative diseases. Although extensive efforts have been done to elucidate all the possible variables related to the aggregation process, much has yet to be done to unveil the main pathways governing protein assembling. In the current work, we induce bovine serum albumin (BSA) association, at pH 3.7, by adding sodium dodecyl sulfate (SDS) and sodium perfluorooctanoate (SPFO) surfactants to BSA solution as promoters of protein aggregation. Firstly, we combine molecular dynamic simulations (MD) to obtain a partially unfolded state of BSA's monomer at the acid pH and small angle X-ray scattering (SAXS) to validate the model. Interestingly, we found by SAXS that at pH 3.7 BSA monomers coexist with dimers in surfactant-free solution. Upon SDS and SPFO addition, the partial unfolded BSA may evolve to large aggregates depending on surfactant concentration. The threshold occurs at 30:1 and 45:1 SDS:BSA and SPFO:BSA molar ratio, respectively, according to turbidity, Thioflavin (ThT) fluorescence, synchrotron radiation circular dichroism (SRCD), SAXS and scanning electron microscopy (SEM) experiments. BSA aggregates are larger in the presence of SDS and structurally more defined upon SPFO binding. Isothermal titration calorimetry (ITC) results give support to infer that both surfactants initially bind to the BSA macromolecule forming a complex. Then, these complexes self-associate towards supramolecular aggregates. Taking into account the physicochemical characteristics of both surfactants and also MD simulations we may suggest that the higher rigidity of the fluorinated chains in respect to hydrogenated ones is crucial to induce more ordered and smaller BSA's aggregates. Our results thus evidence that the ligand structural flexibility might be of a key importance in the pathway of protein aggregation and may pave the way to better understand the early steps of neurodegenerative disorders.

Pleasure: The missing link in the regulation of sleep.

Although largely unrecognized by sleep scholars, sleeping is a pleasure. This report aims first, to fill the gap: sleep, like food, water and sex, is a primary reinforcer. The levels of extracellular mesolimbic dopamine show circadian oscillations and mark the "wanting" for pro-homeostatic stimuli. Further, the dopamine levels decrease during waking and are replenished during sleep, in opposition to sleep propensity. The wanting of sleep, therefore, may explain the homeostatic and circadian regulation of sleep. Accordingly, sleep onset occurs when the displeasure of excessive waking is maximal, coinciding with the minimal levels of mesolimbic dopamine. Reciprocally, sleep ends after having replenished the limbic dopamine levels. Given the direct relation between waking and mesolimbic dopamine, sleep must serve primarily to gain an efficient waking. Pleasant sleep (i.e. emotional sleep), can only exist in animals capable of feeling emotions. Therefore, although sleep-like states have been described in invertebrates and primitive vertebrates, the association sleep-pleasure clearly marks a difference between the sleep of homeothermic vertebrates and cool blooded animals.

Comments on evolution of sleep and the palliopallial connectivity in mammals and birds.

This commentary is referred to the review signed by Rattemborg [N.C. Rattenborg, Evolution of slow wave sleep and palliopallial connectivity in mammals and birds. A hypothesis. Brain Res. Bull. 69 (2006) 20-29]. We propose that the review missed important aspects in relation to the characteristics of sleep in poikilotherm vertebrates and in the evolution of sleep. Poikilotherms continuously show an EEG dominated by slow waves, but its highest amplitude appears not during sleep, but during active waking. In addition, they show an arousal reaction which consists in an increase in EEG amplitude and synchrony, opposite to mammals and birds. As a consequence, most of the conclusions proposed in the review should be rejected.

Antioxidant response analysis in the brain after pilocarpine treatments.

Cholinergic and gabaergic systems play an important role generating electroencephalographic activity and regulating vigilance states. Pilocarpine is a cholinergic agonist commonly used to induce seizures and an epilepticus-like state in rodents. A relationship between status epilepticus and reactive oxygen species has been also suggested which could result in seizure-induced neurodegeneration. The aim of this study was to evaluate the existence of oxidative damage as well as the antioxidant enzyme response in cortex and hippocampus after the administration of an intraperitoneal (350 mg/kg) and an intracerebroventricular (360 microg, 1 microl) pilocarpine injection in rats. The GABA agonist muscimol (1 mg/kg, i.p.), with described neuroprotective properties, was used as a negative control. Only systemic pilocarpine induced oxidative damage. Malondialdehyde levels, as a marker of lipid peroxidation (LP), increased in both regions (55-56%). Catalase (52-80%) and superoxide dismutase (53-60%) activities also rose in both regions but glutathione peroxidase activity only increased in cortex (45%). Glutathione reductase and caspase-3 activity did not change. In conclusion, systemic pilocarpine produced oxidative brain damage, whereas local pilocarpine brain injection had no effects. Moreover, the enzymatic determinations performed in this study are a good tool to study brain injury in pharmacological manipulations such as the ones used in short recording EEG studies.

Why we sleep: the evolutionary pathway to the mammalian sleep.

The cause of sleep is a complex question, which needs first, a clear distinction amongst the different meanings of a causal relationship in the study of a given behavior, second, the requisites to be met by a suggested cause, and third, a precise definition of sleep to distinguish behavioral from polygraphic sleep. This review aims at clarifying the meaning of the question and at showing the phylogenetic origin of the mammalian and avian sleep. The phylogenetic appearance of sleep can be approached through a study of the evolution of the vertebrate brain. This began as an undifferentiated dorsal nerve, which was followed by the development of an anterior simplified brain and ended with the formation of the multilayered mammalian neocortex or the avian neostriate. The successive stages in the differentiation of the vertebrate brain produced, at least, two different waking types. The oldest one is the diurnal activity, bound to the light phase of the circadian cycle. Poikilotherms control the waking from the whole brainstem, where their main sensorymotor areas lie. Mammals developed the thalamocortical lines, which displaced the waking up to the cortex after acquiring homeothermy and nocturnal lifestyle. In order to avoid competence between duplicate systems, the early waking type, controlled from the brainstem, was suppressed, and by necessity was turned into inactivity, probably slow wave sleep. On the other hand, the nocturnal rest of poikilotherms most probably resulted in rapid eye movement sleep. The complex structure of the mammalian sleep should thus be considered an evolutionary remnant; the true acquisition of mammals is the cortical waking and not the sleep.

Improved circadian sleep-wake cycle in infants fed a day/night dissociated formula milk.

On the basis of the circadian nutritional variations present in breast milk, and of the implications for the sleep/wake cycle of the nutrients present in infant formula milks, we designed a formula milk nutritionally dissociated into a Day/Night composition. The goal was to improve the bottle-fed infant's sleep/wake circadian rhythm. A total of 21 infants aged 4-20 weeks with sleeping difficulties were enrolled in the three-week duration study. The sleep analysis was performed using an actimeter (Actiwatch) placed on an ankle of each infant to uninterruptedly record movements during the three weeks. The dissociated Day milk, designed to be administered from 06:00 to 18:00, contained low levels of tryptophan (1.5g/100g protein) and carbohydrates, high levels of proteins, and the nucleotides Cytidine 5 monophosphate, Guanosine 5 monophosphate and Inosine 5 monophosphate. The dissociated Night milk, designed to be administered from 18.00 to 06.00, contained high levels of tryptophan (3.4g/100g protein) and carbohydrates, low levels of protein, and the nucleotides Adenosine 5 monophosphate and Uridine 5 monophosphate. Three different milk-feeding experiments were performed in a double-blind procedure covering three weeks. In week 1 (control), the infants received both by day and by night a standard formula milk; in week 2 (inverse control), they received the dissociated milk inversely (Night/Day instead of Day/Night); and in week 3, they received the Day/Night dissociated formula concordant with the formula design. When the infants were receiving the Day/Night dissociated milk in concordance with their environment, they showed improvement in all the nocturnal sleep parameters analyzed: total hours of sleep, sleep efficiency, minutes of nocturnal immobility, nocturnal awakenings, and sleep latency. In conclusion, the use of a chronobiologically adjusted infant formula milk seems to be effective in improving the consolidation of the circadian sleep/wake cycle in bottle-fed infants.

[The evolution of sleep: birds at the crossroads between mammals and reptiles]. / La evolución del sueño: las aves en la encrucijada entre mamíferos y reptiles.

INTRODUCTION: The evolution of sleep is one of the mysteries surrounding the sleep. Since the discovery of the two phases in the mammalian sleep, NREM and REM, the sleep researchers have unsuccessfully tried to understand their origin and the causes of the sleep duality. Looking for an answer to these questions, the sleep of reptiles (the parental group of mammals) and birds (also descending from reptiles) has been studied. As a result, NREM and REM were found in birds but not in reptiles, and the question remains thus unresolved. DEVELOPMENT AND CONCLUSIONS: This review presents a critical analysis of the published sleep studies developed in birds and points to a possible cause of the conflict: considerable doubts can be cast on the existence of the two sleep phases in birds. If birds turn to have only one sleep phase, they would have a very similar sleep to that of reptiles. As a consequence, the two phases, REM and NREM, would be exclusive of mammals, and both would have appeared as a consequence of the evolutionary changes in the development of the brain from reptiles to mammals.

[Interrelations between sleep and the immune status]. / Interrelaciones entre el sueño y el estado inmune.

INTRODUCTION: The idea of the healing effects of the sleep over the disease is quite extended. Besides, the sleep and the circadian rhythms cause deep changes on the immune function. Reciprocally, the sleep also suffers deep changes when the immune system is challenged during an external aggression. DEVELOPMENT: This review shows some of the data supporting both observations. From the relationships between the sleep and the immune system, it has been proposed that one function of sleep is just to support the immune defense. However, an important fraction of the relationships between sleep and immune function might be a response to the stress produced both during the sleep disorders and when the organism activates the immune defense. Moreover, the epidemiological evidence only shows negligible results when contrasting the amount of sleep and the life expectancy. CONCLUSION: It seems thus probable that the relationships between sleep and immune function are only a reflect of additional factors, such as stress, which cause deep changes in sleep and immunity.

[The work of Santiago Ramón y Cajal in the Revista Trimestral Micrográfica (Trabajos del Laboratorio de Investigaciones Biológicas)]. / La obra de Santiago Ramón y Cajal en Revista Trimestral Micrográfica (Trabajos del Laboratorio de Investigaciones Biológicas).

AIM: This paper is based on a study of Revista Trimestral Micrografica (Trabajos del Laboratorio de Investigaciones Biologicas) between its creation by Santiago Ramon y Cajal in 1896 and his death in 1934. DEVELOPMENT: The journal Revista Trimestral Micrografica was the main way in which Santiago Ramon y Cajal and his school published their work since its creation. Ramon y Cajal created the journal for two main reasons: first, he needed a rapid system to publish his own work; second, the journal could serve to encourage his pupils. The journal published many important reports defending the neuronal theory which expanded the cellular one to include the nervous system.

Temperature drop and sleep: testing the contribution of SWS in keeping cool.

Sleep and body temperature characteristics were studied in man in baseline (B), 24 h-constant routine (CR) and recovery (R) after the CR. The sleep advanced and deepened the trough of the minimum temperature when compared with CR. No relevant difference in minimum body temperature, or in the slope of temperature decrease was found, however, between B and R sleeping nights. No correlation was found between the amount of slow wave sleep and body cooling. The results do not support a homeostatic role of slow wave sleep in brain and/or body cooling.

A new precise microcomputer based rotometer.

The rotometer described here consists of a data acquisition system made of several reed relays which are activated by a small moving magnet when the animal performs rotations. The apparatus has an angular discrimination which is dependent on the number of reed relays used. A simple interface is used to normalize the pulses produced when the reed relay contacts are closed. This normalized output closes key contacts in the keyboard of a microcomputer resulting in ASCII strings. A simple BASIC program is used for computation of various turn fractions. The program also calculates the total number of movements over time, allowing the assessment of activity vs. time.

Non-linear behaviour of human EEG: fractal exponent versus correlation dimension in awake and sleep stages.

The question of whether the finite values of the correlation dimension (D2), used as an index of EEG complexity are due to its chaotic nature or they reflect its behaviour as linearly-correlated noise, remains open. This report aims at clarifying this by measuring D2 and analysing the non-linear nature of EEG through the method of surrogate data as well as by calculating the fractal exponent (beta) via coarse graining spectral analysis (CGSA) in nine adult subjects during waking and sleep states. The results show that even if it is possible to get an estimation of D2 in all states, non-linear structure appears to be present only during slow wave sleep (SWS). EEG exhibits random fractal structure with 1/f(-beta) spectrum (1 < beta < 3) and a negative linear correlation between D2 and beta in all states except during SWS. In consequence, in those states, finite D2 values could be attributed to the fractal nature of EEG and not to the presence of low-dimensional chaos, and therefore, it the use of beta would be more appropriate to describe the complexity of EEG, due to its lower computational cost.

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.

Altered responsiveness to ambiental stimuli in altered thyroidal states.

Hypothyroidal rats produced by low iodine diet or propylthiouracyl (PTU) were less active in the open field and received fewer food reinforcements than controls in a lever press situation at both 22 degrees C and 1 degree C. The hypothyroid rats also pressed less when heat was the reinforcer. On the other hand, hyperthyroidal rats produced by thyroid powder ingestion showed reduced emotionality in the open field. Acute exposure to cold failed to increase their alimentary or heat reinforced behavior. The results suggest that hypothyroidism produces a general inattention to the environment. This is found whether the environmental stimulus is an opportunity to explore, access to food or the availability of external heat.

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.

A simple method for pharmacological separation of motivation attention and learning.

A simple 2 X 2 factorial analysis provides separation of drive and learning aspects in a bar press escape learning. In addition, attentional measure is given considering the dispersion of results. This experimental design has been proved with Diazepam, a drug of rather well known effects, to assert the validity of the method.

Phenol red as indicator of the digestive tract motility in chickens.

Phenol red has been shown to produce no effects on intestinal motility of 24-hour-old chickens, allowing for quantitative measures of gastrointestinal transit and emptying. The results show that 1 hr after ingestion, the main digestive contents are stored in the crop with lesser amounts in the muscular part of the stomach, in the ileum, and in the rectum and caeca.

Polidocanol foam stability in terms of its association with glycerin.

OBJECTIVES: Foam sclerotherapy effectiveness mainly depends on the concentration of the sclerosing agent and foam stability. The objective of this study was to determine if the addition of glycerol at different concentrations contributes to the stability of polidocanol foam. CONTROL GROUP: 3% polidocanol. Group 1: polidocanol 3% + glycerin 1.66%. Group 2: polidocanol 3% + glycerin 3.3%. Group 3: polidocanol 3% + Glycerin 5%. Tessari standard method. Five recordings were made for each mixture. Early visual liquefaction time and half liquid time decay were recorded in seconds. Microscopic measurement of the foams. Mixtures surface tension measurement (N/m). RESULTS: Early visual liquefaction: CONTROL GROUP: 27 (±3.11); Group 1: 67.8 (±6.49); Group 2: 48.6 (±8.2); and Group 3: 35.8 (±4.49). Half-liquid time: CONTROL: 129.2 (±11.00); Group 1: 260.4 (±18.99); Group 2: 224.6 (±13.03); and Group 3: 189.2 (±8.52). Bubbles/mm(2)-diameter-wall thickness: CONTROL: 68-98 µm-7 µm; Group 1: 189-60 µm-9 µm; Group 2: 76-92 µm-12 µm; and Group 3: 49-112 µm-20 µm. Surface tension: CONTROL = 5.54 N/m; Group 1 = 5.45 N/m; Group 2 = 5.35 N/m; and Group 3 = 5.21 N/m. CONCLUSIONS: Small amounts of glycerin highly increase the stability and quality of polidocanol foam. This simple chemical method is easily reproducible and applicable.