Lower body negative pressure enhances oxygen availability in the knee extensor muscles during intense resistive exercise in supine position.

PURPOSE: During exercise in supine posture or under microgravity in space, the gravity-dependent component of local blood pressure in leg muscles at upright posture can be simulated by lower body negative pressure (LBNP). We hypothesized that during resistive exercise LBNP favors oxygen availability in lower extremities, benefiting energy levels and performance of working muscles. METHODS: In permutated crossover design, nine subjects performed a series of fifteen slow-paced concentric (4 s) and eccentric contractions (4 s) without or with 40 mmHg LBNP and 4 s pause between repetitions. The force at knee flexion was 6% of the one repetition maximum (1-RM) and gradually increased to 60% 1RM in the first half of the individual range of motion, subsequently remaining constant until full extension. RESULTS: During the low force periods of continuous exercise, LBNP enhanced the refill of capillary blood measured by near infrared spectroscopy, amplifying the increase of total haemoglobin by about 20 µmol/l (p < 0.01) and oxyhaemoglobin by about 10 µmol/l (p < 0.01). During continuous exercise, LBNP induced a trend towards a lower EMG increment. This LBNP effect was not found when the periods of low forces at knee flexion were extended by 4 s pauses. Increased respiratory oxygen uptake (+ 0.1 l/min, p < 0.05) indicated overall enhanced muscle energy turn-over. CONCLUSIONS: Our results suggest stimulation of oxidative metabolism through LBNP enables working muscles to meet the energy demands of intense exercise. Further research is needed on the consequences for energy metabolism and the molecular control of growth and differentiation.

When neuroscience gets wet and hardcore: neurocognitive markers obtained during whole body water immersion.

Neutral buoyancy facilities are used to prepare astronauts and cosmonauts for extra vehicular activities e.g. on-board of the International Space Station. While previous studies indicated a decrease in cognitive performance in an under water setting, they have only provided behavioural data. This study aimed to review whether recording of electro cortical activity by the use of electroencephalography (EEG) is possible in an under water setting and if so, to identify the influence of water immersion at a depth of 4 m on neurocognitive markers. Ten male subjects performed a cognitive choice-reaction times (RT) task that progressed through five levels of increasing difficulty on land and when submerged 4 m under water. N200 latency and amplitude in the occipital and frontal areas were measured, and baseline cortical activity was measured during rest in both conditions. Neither RT nor amplitude or latency of the N200 showed any significant changes between the land and the under water conditions. Also theta, alpha and beta frequencies showed no differences between the two conditions. The data provided in this study demonstrate the possibility of recording EEG even under the extreme conditions of full body water immersion. The lack of cognitive impairment in RT and N200 in the under water condition may be explained by the fact that only experienced divers participated in the study. As a proof of principle, this study generates many new experimental possibilities that will improve our understanding of cognitive processes under water.

Tautomerization in naphthalenediimines: a keto-enamine Schiff base macrocycle.

[reaction: see text] A new [3 + 3] Schiff base macrocycle incorporating naphthalene groups has been prepared. By examination of its properties, X-ray crystallography of model compounds, and calculations, it has been determined that the macrocycle exists predominantly as the keto-enamine tautomer. This unexpected tautomerization presents an unusual hexaketo interior in the macrocycle.

Highly stable keto-enamine salicylideneanilines.

[reaction: see text] Highly stable NH salicylideneanilines have been prepared by reaction of 1,3,5-triformylphloroglucinol with aniline derivatives. The NH form was confirmed by X-ray crystallographic data, as well as by NMR studies. A convenient one-step synthesis of triformylphloroglucinol is also reported.

N-salicylideneanilines: tautomers for formation of hydrogen-bonded capsules, clefts, and chains.

[structure: see text] The synthesis, characterization, and solid-state structures of new salicylaldimines are reported. Bis(N-salicylideneaniline)s (BSANs) and tris(N-salicylideneaniline)s (TSANs) are sterically encumbered compounds featuring a central six-membered ring in the keto-enamine tautomer. When extended with additional functional groups, these molecules may form hydrogen-bonded capsules, clefts, and extended structures. A TSAN with N-(t)()BOC-o-phenylenediamine groups has been structurally investigated. The complementary hydrogen-bonding motif in this molecule leads it to form dimers in solution and in the solid state. A BSAN with N-(t)()BOC-o-phenylenediamine substituents forms a hydrogen-bonded cleft in solution but forms an extended hydrogen-bonded ladder assembly of cofacial dimers in the solid state. When N-(t)()BOC-1,8-naphthalenediamine was utilized to extend the cleft, an unusual perimidine structure was obtained with the central core in the enol tautomer. In addition, ab initio calculations have been used to support the assignment of the keto-enamine or enol-imine tautomers of the BSANs and TSANs and to predict tautomerization in related BSANs and TSANs.

Virus-assisted loading of polymer nanocontainer.

We present a DNA-containing polymeric nanocontainer using the self-assembled superstructure of amphiphilic block copolymers in aqueous solutions. To demonstrate that DNA translocation is possible across a completely synthetic block copolymer membrane, we have used a phage transfection strategy as a DNA-transfer model system. For this purpose the bacterial channel forming protein LamB was reconstituted in ABA-triblock copolymer vesicles. The outer membrane protein LamB is a specific transporter for maltodextrins but also serves as a receptor for lambda phage to trigger the ejection of lambda phage DNA. We demonstrate that the functionality of the LamB protein is fully preserved despite the artificial surrounding. This leads to a type of polymeric vehicle for DNA that could be useful for gene therapy.