Superoxides from mitochondrial complex III: the role of manganese superoxide dismutase

In this report we show that ubiquinone cytochrome c reductase (complex III) from isolated rat heart mitochondria when inhibited with antimycin A, produces a large amount of superoxide as measured by the chemiluminescent probe coelenterazine. When mitochondria are inhibited with myxothiazol or stigmatellin, there is no detectable formation of superoxide. The antimycin A-sensitive free radical production can be dramatically reduced using either myxothiazol or stigmatellin. This suggests that the antimycin A-sensitive generation of superoxides originates primarily from the Q(o) semiubiquinone. When manganese superoxide dismutase depleted submitochondrial particles (SMP) were inhibited with myxothiazol or stigmatellin, a large superoxide signal was observed. These two inhibitors likely increase the concentration of the Q(i) semiquinone at the N center. The antimycin A-sensitive signal can, in the case of both the mitochondria and the SMP, be dissipated by the addition of copper zinc superoxide dismutase, suggesting that the measured coelenterazine signal was a result of superoxide production. Taken together, this data suggests that free radicals generated from the Q(i) species are more effectively eliminated by MnSOD in intact mitochondria.     

Determination of cardamonin using a chemiluminescent flow-injection method

A sensitive and selective flow injection chemiluminescence method for the determination of cardamonin over the range 1.0 x 10(-8) to 8.0 x 10(-6) g/mL is described. The method is based on the enhancement by cardamonin of the chemiluminescence of the reaction between cerium (IV) and rhodamine 6G in sulphuric acid medium. The optimised flow injection procedure yielded a detection limit for cardamonin of 8.8 x 10(-9) g/mL, whilst the relative standard deviations of intraday and inter-day precision were below 2.5%. The method has the advantages of high sensitivity and a wide linear range. It was successfully applied to the determination of cardamonin in Alpinia katsumadai Hayata. The mechanism of the chemiluminescence reaction is proposed.     

Visual signals in an optomotor reflex: systems and information theoretic analysis

Compensatory optomotor reflexes were examined in crayfish (Procambarus clarkii) with oscillating sine wave gratings and step displacements of a single stripe. A capacitance transducer was used to measure the rotation of the eyestalk about its longitudinal axis. System studies reveal a spatial frequency response independent of velocity and stimulus amplitude and linear contrast sensitivity similar to that of neurons in the visual pathway. The reflex operates at low temporal frequencies (<0.002 Hz to 0.5 Hz) and exhibits a low-pass temporal frequency response with cut-off frequency of 0.1 Hz. Eyestalk rotation increases as a saturable function of the angular stimulus displacement. When compared to the oscillatory response, transient responses are faster, and they exhibit a lower gain for large stimulus displacements. These differences may reflect system nonlinearity and/or the presence of at least two classes of afferents in the visual pathway. Our metric for information transmission is the Kullback-Leibler (K-L) distance, which is inversely proportional to the probability of an error in distinguishing two stimuli. K-L distances are related to differences in responsiveness for variations in spatial frequency, contrast, and angular displacement. The results are interpreted in terms of the neural filters that shape the system response and the constraints that the K-L distances place on information transmission in the afferent visual pathway.     

Mesenchymal stem cell conditioned medium increases glial reactivity and decreases neuronal survival in spinal cord slice cultures

Ex vivo spinal cord slice cultures (SCSC) allow study of spinal cord circuitry, maintaining stimuli responses comparable to live animals. Previously, we have shown that mesenchymal stem/stromal cell (MSC) transplantation in vivo reduced inflammation and increased nerve regeneration but MSC survival was short-lived, highlighting that beneficial action may derive from the secretome. Previous in vitro studies of MSC conditioned medium (CM) have also shown increased neuronal growth. In this study, murine SCSC were cultured in canine MSC CM (harvested from the adipose tissue of excised inguinal fat) and cell phenotypes analysed via immunohistochemistry and confocal microscopy. SCSC in MSC CM displayed enhanced viability after propidium iodide staining. GFAP immunoreactivity was significantly increased in SCSC in MSC CM compared to controls, but with no change in proteoglycan (NG2) immunoreactivity. In contrast, culture in MSC CM significantly decreased the prevalence of βIII-tubulin immunoreactive neurites, whilst Ca²⁺ transients per cell were significantly increased. These ex vivo results contradict previous in vitro and in vivo reports of how MSC and their secretome may affect the microenvironment of the spinal cord after injury and highlight the importance of a careful comparison of the different experimental conditions used to assess the potential of cell therapies for the treatment of spinal cord injury.     

Characterization of sarcoplasmic reticulum Ca2+ ATPase nucleotide binding domain mutants using NMR spectroscopy

T-type Ca²⁺ channels have been implicated in tremorogenesis and motor coordination. The α1 subunit of the Ca_V3.1 T-type Ca²⁺ channel is highly expressed in motor pathways in the brain, but knockout of the Ca_V3.1 gene (α1G^-/-) per se causes no motor defects in mice. Thus, the role of Ca_V3.1 channels in motor control remains obscure in vivo. Here, we investigated the effect of the Ca_V3.1 knockout in the null genetic background of α1 GABA_A receptor (α1^−/−) by generating the double mutants (α1^−/−/α1G^-/-). α1^−/−/α1G^-/- mice showed severer motor abnormalities than α1^−/− mice as measured by potentiated tremor activities at 20 Hz and impaired motor learning. Propranolol, an anti-ET drug that is known to reduce the pathologic tremor in α1^−/− mice, was not effective for suppressing the potentiated tremor in α1^−/−/α1G^-/- mice. In addition, α1^−/−/α1G^-/- mice showed an age-dependent loss of cerebellar Purkinje neurons. These results suggest that α1^−/−/α1G^-/- mice are a novel mouse model for a distinct subtype of ET in human and that Ca_V3.1 T-type Ca²⁺ channels play a role in motor coordination under pathological conditions.     

Mate availability affects female choice in a fish with paternal care: female counterstrategies against male filial cannibalism

Theory predicts that individuals should adopt counterstrategies against intersexual conflict with their mating partners if the counterstrategies are effective and cost-efficient. In fishes, males with parental care often cannibalize their own offspring, which reduces the female’s fitness and creates intersexual conflicts. Males of the goby Rhinogobius flumineus cannibalize more eggs in the nest when they have access to additional females prior to spawning. Thus, it is predicted that females will strategically avoid spawning with males that have high mate availability. In the present study, we experimentally tested this prediction. When sexual pairs were placed in tanks, most females (control females; 21/22) successfully spawned inside the nest. In contrast, when a gravid female (stimulus female) that was housed in a small transparent cage was shown to the experiment pairs prior to spawning, only about half of the females (experiment females; 16/29) spawned inside the nest; the remaining females released unfertilized eggs outside of the nest. Moreover, experiment females infrequently accepted and followed males into nests, and delayed spawning more often than control females. R. flumineus females prefer males that court frequently. Indeed, experiment females that infrequently received courtship tended to spawn outside of the nest. However, infrequent courtship alone could not explain outside-nest spawning, delay in spawning, or the shorter stay of females in nests. These results imply that the presence of a stimulus female dampens female spawning with males. We suggest that R. flumineus females may strategically reject or hesitate to spawn with males that have high mate availability, and that this spawning avoidance may be a counterstrategy against male filial cannibalism.     

Socio demographic and lifestyle factors of metabolic syndrome among adult rural indigenous Malaysian population from Perak State,Malaysia

Metabolic syndrome (MetS) is defined as a cluster of known disorders that increase the risk for morbidity and mortality from cardiovascular diseases (CVD) and type 2 diabetes mellitus. This cross sectional study was carried out to estimate the prevalence of MetS using Adult Treatment Panel 3 (ATP 3) classification and socio-demographic and lifestyle factors contributing to metabolic syndrome among rural indigenous Malaysian population from Perak state, Malaysia which included 148 rural Malay and 145 Orang Asli(OA) individuals. This community based cross-sectional study revealed that the prevalence of MetS was significantly higher among Malays (27.7%) as compared to Orang Aslis (13.8%). Overall Prevalence of Metabolic syndrome in the rural indigenous Malaysian population was 20.8%. Prevalence of abdominal obesity and high blood pressure were significantly higher among Malays as compared to OA population. Metabolic syndrome was significantly higher among those above 45 years of age group in overall rural indigenous Malaysian population and among OA. The prevalence of MetS was significantly higher among those who were obese and overweight and among Malays who were regularly taking snacks between meals. There was no significant association between other dietary risk factors, smoking, alcohol use or physical activity with metabolic syndrome.