Fiber reinforced hydrated networks recapitulate the poroelastic mechanics of articular cartilage.

The role of poroelasticity on the functional performance of articular cartilage has been established in the scientific literature since the 1960s. Despite the extensive knowledge on this topic there remain few attempts to design for poroelasticity and to our knowledge no demonstration of an engineered poroelastic material that approaches the physiological performance. In this paper, we report on the development of an engineered material that begins to approach physiological poroelasticity. We quantify poroelasticity using the fluid load fraction, apply mixture theory to model the material system, and determine cytocompatibility using primary human mesenchymal stem cells. The design approach is based on a fiber reinforced hydrated network and uses routine fabrication methods (electrohydrodynamic deposition) and materials (poly[ɛ-caprolactone] and gelatin) to develop the engineered poroelastic material. This composite material achieved a mean peak fluid load fraction of 68%, displayed consistency with mixture theory, and demonstrated cytocompatibility. This work creates a foundation for designing poroelastic cartilage implants and developing scaffold systems to study chondrocyte mechanobiology and tissue engineering. STATEMENT OF SIGNIFICANCE: Poroelasticity drives the functional mechanics of articular cartilage (load bearing and lubrication). In this work we develop the design rationale and approach to produce a poroelastic material, known as a fiber reinforced hydrated network (FiHy™), that begins to approach the native performance of articular cartilage. This is the first engineered material system capable of exceeding isotropic linear poroelastic theory. The framework developed here enables fundamental studies of poroelasticity and the development of translational materials for cartilage repair.

[The effect of an acoustic calling signal on the sex hormone level in the blood of white mice]. / Vliianie akusticheskogo prizyvnogo signala na uroven' polovykh gormonov v krovi belykh myshei.

The action was studied of synthesized acoustic signals, similar to the natural invocatory ones by their characteristics, on the level of sexual hormones in male and female mature laboratory mice, and also the dependence of these hormonal shifts on rhythmic organization of the artificial sound signals. As a result of the experiments it was convincingly shown that synthesized acoustic signal with the frequency of 3500 Hz (S-1) caused a functional load on the glands of internal secretion which was testified by statistically significant increase in the level of sexual hormones in the blood of males (by testosterone and extradiole) and female mice (by extradiole and progesterone). In order to clear up the role of rhythmic organization of signal studies were conducted with the application of synthetic acoustic signal (S-2), different from S-1. The analysis of the data revealed the absence of significant changes in the level of sexual hormones both in males and in females during S-2 sounding.

Impulse activity of medulla oblongata in rats in response to stimulation of taste receptors and visceral chemoreceptors.

We have recorded extracellularly the impulse activity of the rat medulla oblongata during stimulation of taste receptors of the tongue and visceral chemoreceptors with solutions of hydrochloric acid and sodium chloride. We have detected in the caudal region of the nucleus of the solitary tract, neurons that react to the chemical stimulation of either one or both the receptive zones mentioned. The response reactions of the isolated groups of units (taste, viscerochemical, and convergent neurons) are tonic and are characterized by a high level of impulse activity. We have established that the neurons of each of the groups isolated are capable of discriminating between salt and acid solutions. Using the example of sodium chloride solutions we have shown that an increase in the number of viscerochemical neurons which inhibit their own background activity on increase in the concentration of any substance in the intestine is an important index of the satiation of an animal and can serve as a starting link in the mechanism of food rejection.

[Impulse activity of the rat medulla oblongata in response to stimulation of taste receptors and visceral chemoreceptors]. / Impul'snaia aktivnost' prodolgovatogo mozga krys v otvet na razdrazhenie vkusovykh retseptorov i vistseral'nykh khemoretseptorov.

The unit activity from the medulla oblongata was extracellularly recorded during stimulation of taste receptors and visceral chemoreceptors of small intestine with the solutions of hydrochloric acid and sodium chloride. Neurons responding to the chemical stimulation are at the caudal part of nucleus tractus solitarius. Responses of taste, viscerochemical and convergence units are tonic and their discharge rates are low. The ability for chemical stimulus graduation analysis characterizes each group of units. Increased concentration of the solutions in intestine brings about the increase in the number of viscerochemical neurons with inhibited background activity. This may be the index of satiation and serve as a starting link in the mechanism of food rejection.

[Physiological analysis of food motivation in experimentally induced water-salt imbalance]. / Fiziologicheskii analiz pishchevoi motivatsii v usloviiakh éksperimental'no vyzvannogo narusheniia vodno-solevogo balansa.

Internal or motivational factors and external or signal factors were assessed to determine their role in motor-food response during conditioning in cats and dogs. Under experimental water-salt dysbalance visceral signalling was shown to be an essential factor involved in a goal-directed response. In addition to dominant motivation, a conditioned food signal seems to be this factor. In search for neurophysiological correlates of food motivation, we studied responses of n. tractus solitaris in rats to adequate chemical stimulation of the tongue receptors and viscerochemoreceptors. 3 groups of neurons were distinguished: those responding to the stimulation of only one receptive zone (taste and viscerochemical neurons) and neurons responding to the stimulation of both receptive areas ("convergence" units). Under salt deprivation, threshold concentrations of salt for responses from n. solitaris decreased and the response from a convergence neuron to viscerochemical stimulation diminished following application of sodium chloride on the tongue receptor.

[Neuronal activity of the frog medulla oblongata in response to chemical stimulation of gustatory and cutaneous chemoreceptors]. / Neironnaia aktivnost' prodolgovatogo mozga liagushki pri khimicheskom razdrazhenii vkusovykh i kozhnykh khemoretseptorov.

The unit activity of medulla oblongata extracellularly recorded during stimulation of the taste receptors and skin chemoreceptors with solutions of the hydrochloric and citric acids, sodium chloride and potassium chloride, in the majority of neurons responded at least to the solutions of one acid and one salt. The number of units which responded to all the solutions was twice as high on stimulation of taste receptors than skin chemoreceptors. The chemical stimuli graduation analysis is more suitable in the case of taste receptor stimulation. The peculiarities of the primary center unit activity response to the stimulation of the receptive fields in question may be connected with different role of taste and skin chemoreceptors in adaptive behaviour.