Volatile fatty acids as indicators of process imbalance in anaerobic digestors

In continuously stirred tank reactor experiments, with manure as substrate at thermophilic temperatures, the use of volatile fatty acids (VFA) as process indicators was investigated. Changes in VFA level were shown to be a good parameter for indicating process instability. The VFA were evaluated according to their relative changes caused by changes in hydraulic loading, organic loading or temperature. Butyrate and isobutyrate together were found to be particularly good indicators. Butyrate and isobutyrate concentrations increased significantly 1 or 2 days after the imposed perturbation, which makes these acids suitable for process monitoring and important for process control of the anaerobic biological system. In addition it was shown in a batch experiment that VFA at concentrations up to 50 mM did not reduce the overall methane production rate. This showed that VFA accumulation in anaerobic reactors was the result of process imbalance, not the cause of inhibition, thus justifying the use of VFA as process indicators.     

Evidence indicating that pig renal phosphate-activated glutaminase has a functionally predominant external localization in the inner mitochondrial membrane

Phosphate-activated glutaminase in intact pig renal mitochondria was inhibited 50-70% by the sulfhydryl reagents mersalyl and N-ethylmaleimide (0.3-1.0 mM), when assayed at pH 7.4 in the presence of no or low phosphate (10 mM) and glutamine (2 mM). However, sulfhydryl reagents added to intact mitochondria did not inhibit the SH-enzyme beta-hydroxybutyrate dehydrogenase (a marker of the inner face of the inner mitochondrial membrane), but did so upon addition to sonicated mitochondria. This indicates that the sulfhydryl reagents are impermeable to the inner membrane and that regulatory sulfhydryl groups for glutaminase have an external localization here. The inhibition observed when sulfhydryl reagents were added to intact mitochondria could not be attributed to an effect on a phosphate carrier, but evidence was obtained that pig renal mitochondria have also a glutamine transporter, which is inhibited only by mersalyl and not by N-ethylmaleimide. Mersalyl and N-ethylmaleimide showed nondistinguishable effects on the kinetics of glutamine hydrolysis, affecting only the apparent Vmax for glutamine and not the apparent Km calculated from linear Hanes-Woolf plots. Furthermore, both calcium (which activates glutamine hydrolysis), as well as alanine (which has no effect on the hydrolytic rate), inhibited glutamine transport into the mitochondria, indicating that transport of glutamine is not rate-limiting for the glutaminase reaction. Desenzitation to inhibition by mersalyl and N-ethylmaleimide occurred when the assay was performed under optimal conditions for phosphate activated glutaminase (i.e. in the presence of 150 mM phosphate, 20 mM glutamine and at pH 8.6). Desenzitation also occurred when the enzyme was incubated with low concentrations of Triton X-100 which did not affect the rate of glutamine hydrolysis. Following incubation with [14C]glutamine and correction for glutamate in contaminating subcellular particles, the specific activity of [14C]glutamate in the mitochondria was much lower than that of the surrounding incubation medium. This indicates that glutamine-derived glutamate is released from the mitochondria without being mixed with the endogenous pool of glutamate. The results suggest that phosphate-activated glutaminase has a functionally predominant external localization in the inner mitochondrial membrane.     

Interrelations between sympathetic adrenal and opioid systems--regulatory mechanism determining cardiac resistance to stress damage]

The present paper has analyzed relationship between sympatico-adrenal and opioid systems in the pathogenesis of stress heart damage. Based on the our own results and other investigator data the authors make a conclusion that namely relationship between opioid and sympatico-adrenal systems both on the level of the brain and on the periphery determines a degree of the heart resistance to the injury action of severe stress. Myocardial protection by opioids at stress was found to be mediated by the peripheral mu-opioid receptors and was associated with decrease in an activity of sympatico-adrenal system and a inhibition of its effector part. On contrary central opioid system activation leads to an increase in stress heart damage via an increase in sympathetical influence on the myocardium.     

The lagena (the third otolith endorgan in vertebrates)

In this review, the structure and functions of the lagena (the third otolith organ) in an evolutionary lineage of the vertebrates are described and discussed. The lagenar macula appears first in the posterior part of the sacculus of elasmobranchs; in these animals, the lagena is considered to be involved in the balance support (orientation with respect to the gravitation force). The lagena as a separate endorgan has been described in teleost fishes; in some species, the lagena is connected with the sacculus, while in other species the interrelations of these structures can be dissimilar. The lagena supplements the functions of the sacculus; in fishes (animals with no special organ of hearing), it is involved in discrimination of sound oscillations, identification of the gravitation vector, and orientation in the course of movements within the vertical plane. In amphibians, the lagena is localized in the posterior part of the sacculus, near the auditory structures; it performs mostly vestibular and (to a much lesser extent) auditory functions. In amniotes, the lagena was first separated from the sacculus; it is localized in the cochlear canal, distally with respect to the hearing organ. Information on the functions of the lagena in amniotes is rather limited and contradictory. Central projections of this organ have been examined practically only in birds. Lagenar afferents project to the vestibular nuclei and cerebellum, while some fibers come to the auditory nuclei of the medulla. The lagena in birds can be related to their navigation abilities (birds are supposed to be capable of orienting within the magnetic field of the Earth due to the magnetic properties of the lagenar otoconia; this structure can also provide detection of movements along the vertical axis. The close proximity between the otolithic and auditory endorgans in the cochlear canal of amniotes can be indicative of the functional significance of these interrelations. This aspect, however, remains at present undiscovered. In mammals (except Monotremata), there is no lagena as an independent endorgan. Neirofiziologiya/Neurophysiology, Vol. 40, No. 2, pp. 160–178, March–April, 2008.