The differences between sexes and strains in the capacity to acquire a passive avoidance conditioned reflex in KLA- and KHA-strain rats

The interstrain differences in passive avoidance conditioning were studied in male and female KHA (Koltushi High Avoidance) and KLA (Koltushi Low Avoidance) rats. These strains were selected for the rate of acquisition of active avoidance in a shuttle box. It was shown that the passive avoidance was substantially better acquired in the KLA strain than in the KHA. In females KHA rats the capability for passive avoidance conditioning depended on the estrus phase: the conditioning was impossible in proestrus.     

Energy sources for glutamate neurotransmission in the retina: absence of the aspartate/glutamate carrier produces reliance on glycolysis in glia

The mitochondrial transporter, the aspartate/glutamate carrier (AGC), is a necessary component of the malate/aspartate cycle, which promotes the transfer into mitochondria of reducing equivalents generated in the cytosol during glycolysis. Without transfer of cytosolic reducing equivalents into mitochondria, neither glucose nor lactate can be completely oxidized. In the present study, immunohistochemistry was used to demonstrate the absence of AGC from retinal glia (Müller cells), but its presence in neurons and photoreceptor cells. To determine the influence of the absence of AGC on sources of ATP for glutamate neurotransmission, neurotransmission was estimated in both light- and dark-adapted retinas by measuring flux through the glutamate/glutamine cycle and the effect of light on ATP-generating reactions. Neurotransmission was 80% faster in the dark as expected, because photoreceptors become depolarized in the dark and this depolarization induces release of excitatory glutamate neurotransmitter. Oxidation of [U-14C]glucose, [1-14C]lactate, and [1-14C]pyruvate in light- and dark-adapted excised retinas was estimated by collecting 14CO2. Neither glucose nor lactate oxidation that require participation of the malate/aspartate shuttle increased in the dark, but pyruvate oxidation that does not require the malate/aspartate shuttle increased to 36% in the dark. Aerobic glycolysis was estimated by measuring the rate of lactate appearance. Glycolysis was 37% faster in the dark. It appears that in the retina, ATP consumed during glutamatergic neurotransmission is replenished by ATP generated glycolytically within the retinal Müller cells and that oxidation of glucose within the Müller cells does not occur or occurs only slowly.     

Strain dependent response of circadian rhythms during exposure to continuous illumination

Enzymes activities were measured, at three hours intervals, during 30 hours, in various tissues of C57BL/6J and A/J male mice. The measurements, were carried out on mice which were exposed for two, five and twenty one days to continuous illumination. Identical measurements were performed also on mice which were kept in alternating 14 hours light: 10 hours dark. Activity patterns of each group were analysed to test the presence, or absence, of rhythm characteristics. The results of the experiments with C57BL/6J have been previously reported. The comparison of the results, which were obtained from the two strains revealed that under exposure to alternating light: dark conditions all activity patterns exhibited a significant circadian rhythm. Except for one enzyme (thymus GAPD), the times of peak activity (acrophase) were identical for all other examined enzymes, in both strains. On the other hand when the two strains were exposed to continuous illumination they differed in their response to the effect of continuous light. The activity of the same enzyme exhibited different periodicity and/or different acrophase in each of the two strains. This variability reflects the existence of genetic differences, between the strains in the free running behavior of these enzymes' activity rhythms.     

Low dose of disulfiram and l-dopa evoked synergistic modification in behavior of Wistar and WAG/Rij rats

Comparative analysis of behaviors of two rat strains, Wistar and WAG/Rij, was performed. No behavioral differences between Wistar and WAG/Rij were found in the emotional resonance test. Disulfiram injection produced similar effects in both rat strains. Animals of the first group (with slow acquisition of emotional resonance reaction) transformed into the animals of the second group (with fast acquisition). Passive avoidance conditioning was successfully reproduced in Wistar and was significantly impaired in WAG/Rij. A low dose of disulfiram injected before or immediately after conditioning substantially improved the reproduction to a greater extent in WAG/Rij than Wistar strains thus eliminating in interstrain differences. Active avoidance conditioning was more successful in WAG/Rij than in Wistar rats However, on the next day conditioning in WAG/Rij was substantially impaired. Administration of the low dose of disulfiram or L-DOPA prior to conditioning impaired the acquisition but improved the reproduction on the following day in both strains, but disulfiram injection after conditioning improved conditioning in WAG/Rij to a greater extent than in Wistar. Thus, the pharmacologic enhancement of the reward system substantially changed animal behavior and improved memory consolidation.     

Diurnal and nocturnal functional response of juvenile Notonecta maculata considered as a consequence of shifting predation behaviour

Presence or absence of light is considered to significantly affect predation within freshwater communities. In relation to light regime, the scope of the present study is to identify proximate factors accounting for different rates of predation in juvenile Notonecta maculata. It has been shown that foraging of juvenile N. maculata on Daphnia magna is reduced under dark conditions. These differences are accounted for by the presence/absence of light and are not regulated by any endogenous circadian rhythm. Direct observation of predation components revealed that in the dark, daphnid prey is detected at shorter distances, thus lowering the rate of encounter which finally results in a decreasing number of prey items eaten. Handling time was found to significantly increase during dark periods. Since the amount of food ingested per prey item increases to a certain extent with increasing handling time, it is suggested that the decreasing number of daphnids consumed is compensated by gaining a higher amount of food per item during a lengthier, more thorough, handling of the prey. A mechanistic model that describes the foraging process along a general predation cycle was parameterized based on the results of direct observations, instead of using classic functional response curves. This allows the comparison of model output to independent functional response data. A good correlation between observed and predicted data confirms the assumption that the reduction of the nocturnal predation rate is caused by shifting predation behaviour and indicates that the crucial light/dark differences in the foraging of N. maculata are considered in the approach.     

The co-existence between DSE and AMF symbionts affects plant P pools through P mineralization and solubilization processes

The capacity of dark septate endophytes (DSE; Phialocephala turiciensis, Acephala applanata, P. glacialis and Phaeomollisia piceae) to solubilize inorganic phosphate (P) and to mineralize the organic form was studied. We analysed the effect of DSE strains on P uptake by Trifolium repens in the presence or absence of arbuscular mycorrhizal fungi (AMF). Phosphatases were observed both in the absence of the host plant and the organic resource, showing that the P mineralization process is not induced by the enzyme substrate or the host. DSE were more efficient at mineralizing organic P. Independently of the presence of AMF, DSE increased the pool of P in the soil, with significant differences being found in P levels among the different DSE. In contrast, plant P uptake was increased by AMF. The P content of plants increased with the co-inoculation of AMF and P. turiciensis or P. piceae. We hypothesize a close relationship between DSE and AMF in relation to P availability and uptake in plants. Whereas DSE increase the pool of P in the rhizosphere, AMF are responsible for P transfer to the host, with co-colonization of plants by DSE and AMF showing a synergistic outcome.     

The function of redox shuttles during aerobic glycolysis in two strains of Ehrlich ascites tumor cells

The function of glycerophosphate and malate-aspartate shuttles during glucose metabolism in two strains of Ehrlich ascites tumor cells was evaluated by several experimental approaches. The activities of the enzymes involved in these shuttle systems were assayed in the cytosolic and mitochondrial compartments after cell fractionation by the digitonin method. The glycerophosphate shuttle can be ruled out because of the lack of relevant enzymatic activities, and the failure of glucose to increase rotenone-inhibited respiration. Analysis of glycolytic flux in the presence of aminooxyacetate indicates that the activity of malate-aspartate shuttle may be very low. Balance studies of glucose uptake and lactate production suggest the existence of other pathways for the reoxidation of cytosolic NADH, which are acetyl-CoA dependent. Estimation of citrate synthase and ATP citrate lyase, in addition to the observed high activity of malate dehydrogenase, suggests a malate-citrate shuttle.     

Typological features of behavior and memory in Norway rats selected for absence of aggression toward a man

Features of behavior and retrieval of passive conditioned avoidance on a new and forgotten stimuli were compared in Wistar rats and Norway rats bred for the absence of aggression toward a man. As distinct from white rats, grey rats were characterized by low anxiety and high locomotor exploratory activity in the elevated plus maze and dark-light chamber. Norway rats demonstrated better avoidance performance with active defensive behavioral strategy than Wistar rats. Latent inhibition during conditioning with a previously forgotten situational stimulus was the same in both rat strains. The results are discussed in terms of the use of grey rats as a model for an in-depth analysis of the mechanisms of memory optimization.     

Analysis of the striato-pallidal interactions in regulation of avoidance behavior

Impairment of avoidance conditioning in the shuttle box was found in rats with bicuculline intrapallidal administration, as well as activation of the conditioning and stereotyped movements during amphetamine intrastriatal administration. These neuropharmacological effects upon both ganglia areas induced dynamic behavioural changes in the avoidance conditioning and open-field locomotor activity. The findings suggest involvement of neostriatalpallidal relationship in control of avoidance conditioning and complex behavioural acts.     

Biological effects of dyes on bacteria. VI. Mutation induction by acridine orange and methylene blue in the dark with special reference to Escherichia coli WP6 (polA1)

Acridine orange (AO) and methylene blue (MB) in the dark were shown to be weak to moderate mutagens (induction of resistance to T5 phage) in repair-deficient strains of Escherichia coli B/r. However, strain WP2 (wild-type) was not mutated by AO in the dark, in confirmation of earlier data. The presence of 2 microM AO reduced by 41% the spontaneous mutation rate in strain WP2, from 4.1 to 2.4 mutants/10(8) cells/generation. In the polymerase I-deficient strain WP6 (polA1), 2 microM AO increased the mutation rate in the dark 14-fold. We propose that both spontaneous and AO-induced mutagenesis in the absence of light occur at the site of semiconservative DNA replication. If the intercalation mechanism for the effects in the absence of light is valid, the wild-type strain (WP2) may be resistant to frameshift mutagenesis induced by intercalated compounds, while the polymerase I-deficient strain (WP6) may be highly suceptible to the presence of an intercalated dye such as AO at the DNA-replication fork. MB and AO likely act through different mechanisms since MB is only a moderate mutagen in strain WP6 and the other repair-deficient strains tested.     

Disruption of a type II endonuclease (TDE0911) enables Treponema denticola ATCC 35405 to accept an unmethylated shuttle vector

The oral spirochete Treponema denticola is associated with human periodontal disease. T. denticola ATCC 35405 and ATCC 33520 are two routinely used laboratory strains. Compared to T. denticola ATCC 33520, ATCC 35405 is more virulent but less accessible to genetic manipulations. For instance, the shuttle vectors of ATCC 33520 cannot be transformed into strain ATCC 35405. The lack of a shuttle vector has been a barrier to study the biology and virulence of T. denticola ATCC 35405. In this report, we hypothesize that T. denticola ATCC 35405 may have a unique DNA restriction-modification (R-M) system that prevents it from accepting the shuttle vectors of ATCC 33520 (e.g., the shuttle plasmid pBFC). To test this hypothesis, DNA restriction digestion, PCR, and Southern blot analyses were conducted to identify the differences between the R-M systems of these two strains. DNA restriction digestion analysis of these strains showed that only the cell extract from ATCC 35405 was able to digest pBFC. Consistently, PCR and Southern blot analyses revealed that the genome of T. denticola ATCC 35405 encodes three type II endonucleases that are absent in ATCC 33520. Among these three endonucleases, TDE0911 was predicted to cleave unmethylated double-stranded DNA and to be most likely responsible for the cleavage of unmethylated pBFC. In agreement with this prediction, the mutant of TDE0911 failed to cleave unmethylated pBFC plasmid, and it could accept the unmethylated shuttle vector. The study described here provides us with a new tool and strategy to genetically manipulate T. denticola, in particular ATCC 35405, and other strains that may carry similar endonucleases.     

Acetate Metabolism by an Obligate Phototrophic Strain of Pandorina morum1

SYNOPSIS. Acetate metabolism was studied in 2 strains of the green alga Pandorina morum. Both strains were capable of mixotrophic growth in the light, but only one strain was capable of heterotrophic growth in the dark. ¹⁴C-2-acetate uptake by both strains was studied in the light and dark, in the presence and absence of CO₂ and 3(3,4-dichlorophenyl)-1,1-dimethylurea (10^?5M). The distribution of radioactivity incorporated into the insoluble, aqueous and chloroform soluble fractions of the cells was determined. The strain incapable of heterotrophic growth in the dark was found to incorporate very little acetate in the dark, and its ability to incorporate acetate into the insoluble fraction was severely limited under all conditions. Incorporation into the aqueous and chloroform-soluble fractions in the light was similar in both strains. The reduced incorporation into the insoluble fraction was almost totally the result of limited incorporation of acetate into polysaccharides by the obligate phototrophic strain.     

Effects of dehydration on renal aminopeptidase activities in adult male and female rats

Orexin A injected into the lateral hypothalamus (LH) stimulates feeding and activates neurons in brain sites regulating feeding and arousal. The feeding effects of orexin A have been demonstrated during the light cycle, a time when rats are normally resting, and the effect of orexin A on activity after injection into the LH has not been previously measured. Thus, it is unclear whether LH orexin A-induced feeding is secondary to enhanced arousal. To address this, LH-cannulated rats habituated to a running wheel were injected with either orexin A (1000 pmol) or vehicle during light and dark cycles. Food intake and running wheel rotations were measured for 2 h. Spontaneous physical activity (SPA) was also measured during the dark cycle. During the light cycle, orexin A in the LH stimulated feeding in the presence and absence of a running wheel and increased number of running wheel rotations in the presence and absence of food. During the dark cycle, orexin A in the LH induced SPA (+/- presence of food), but had no effect on feeding. These data show that LH orexin A stimulation of feeding is not always coincident with increased activity, suggesting that feeding induced by LH-injected orexin A is not consequent to enhanced arousal.     

Anaerobic heterotrophic dark metabolism in the cyanobacterium Oscillatoria limnetica: Sulfur respiration and lactate fermentation

The cyanobacterium Oscillatoria limnetica, capable of anoxygenic photosynthesis in the light with sulfide as electron donor can anaerobically break down its intracellular polyglucose in the dark. In the absence of elemental sulfur, the organism carries out lactate fermentation; in its presence, anaerobic respiration occurs in which sulfur is reduced to sulfide. Induction of anoxygenic photosynthesis or synthesis of new proteins is not necessary for either process. Cells adapted in the dark to sulfur reduction are capable of anoxygenic photosynthesis during a subsequent light period, unless protein synthesis has been inhibited during the dark incubation period.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - FCCP Carbonylcyanide p-trifluoromethoxyphenylhydrazone - mgat milligramatom - OD optical density     

Uninduced ammonia release by the nitrogen-fixing cyanobacterium Anabaena

Abstract Certain strains of the nitrogen-fixing cyanobacterium Anabaena were found to release varying quantities of ammonia without any induction, both in the presence and absence of combined nitrogen (nitrate) in the medium, during the different phases of their growth. In general, growth and ammonia release were comparable in both media, although there were strain differences. 3 patterns of ammonia release were observed in different strains during the growth period. They were: (1) release pattern parallel to the growth curve; (2) a continuous increase in release; and (3) release showing a bimodal curve.     

Physical characteristics that predict functional performance in Division I college football players

Strength and conditioning professionals who work with collegiate football players focus much of their time and effort on developing programs to enhance athletic performance. Although there has been much speculation, there is little scientific evidence to suggest which combination of physical characteristics best predicts athletic performance in this population. The purpose of this investigation was to examine the relationship among 6 physical characteristics and 3 functional measures in college football players. Data were gathered on 46 NCAA Division I college football players. The 3 response variables were 36.6-m sprint, 18.3-m shuttle run, and vertical jump. The 6 regressor variables were height, weight, percentage of body fat, hamstring length, bench press, and hang clean. A stepwise multiple regression analysis was performed to screen for variables that predict physical performance. Regression analysis revealed clear prediction models for the 36.6-m sprint and 18.3-m shuttle run. The results of this investigation will help strength and conditioning specialists better understand the variables that predict athletic performance in Division I college football players.     

Genotype-dependent interactions among sympatric Microcystis strains mediated by Daphnia grazing

Natural populations of the bloom forming cyanobacterium Microcystis are typically composed of several distinct genotypes. Using Microcystis strains that differ in growth rate, microcystin production and colony formation, we conducted a laboratory experiment in the presence and absence of a grazer, the water flea Daphnia, to investigate whether interactions among strains can be predicted from functional traits, and whether the outcome of competition between strains is influenced by a grazer. Two toxic and two non‐toxic Microcystis strains, isolated from a single lake, were grown during four weeks as single strains, in all possible combinations of two strains and all together, in the presence and absence of Daphnia magna. The relative abundance of strains in the populations was assessed using denaturing gradient gel electrophoresis, and the growth rate of each strain in mixed populations was compared to its growth rate in monoculture to determine interactions between strains. The observed interactions were strain‐specific, and the relative abundances of strains in mixed populations could be partially explained by taking toxicity and colony formation into account. Importantly, some of the interactions were strongly altered by the presence of Daphnia. Daphnia induced colony formation in one strain, which then became a better competitor. Daphnia grazing also caused a higher evenness in the populations, both through a weakening of competitive interactions as well as by facilitation effects. Strong facilitation effects were due to non‐toxic strains benefiting from the protection offered by toxic strains in the presence of predation. Overall, our results emphasize the presence of strong competitive interactions between Microcystis strains in the absence of grazing, whereas indirect positive interactions are prevalent in the presence of a generalist grazer. Our results suggest that differences in functional traits and grazer‐mediated facilitation effects may enhance coexistence of Microcystis strains, including toxic and non‐toxic strains.     

Relation between the learning of young rainbow trout in a shuttle-box and survival in the presence of an unfamiliar predator

The analysis of the curves of acquisition of a conditioned reflex (CR) in a shuttle box allowed to reveal three stages of this process and establish in two-year rainbow trouts the presence of four types of individuals differing in the dynamics of processes of the CR formation. A direct positive connection is established between the speed of learning in a shuttle box and surviving of young fish in the presence of artificial predator.     

Pulmonary surfactant protein A interacts with gel-like regions in monolayers of pulmonary surfactant lipid extract

Epifluorescence microscopy was used to investigate the interaction of pulmonary surfactant protein A (SP-A) with spread monolayers of porcine surfactant lipid extract (PSLE) containing 1 mol % fluorescent probe (NBD-PC) spread on a saline subphase (145 mM NaCl, 5 mM Tris-HCl, pH 6.9) containing 0, 0.13, or 0.16 microg/ml SP-A and 0, 1.64, or 5 mM CaCl(2). In the absence of SP-A, no differences were noted in PSLE monolayers in the absence or presence of Ca(2+). Circular probe-excluded (dark) domains were observed against a fluorescent background at low surface pressures (pi approximately 5 mN/m) and the domains grew in size with increasing pi. Above 25 mN/m, the domain size decreased with increasing pi. The amount of observable dark phase was maximal at 18% of the total film area at pi approximately 25 mN/m, then decreased to approximately 3% at pi approximately 40 mN/m. The addition of 0.16 microg/ml SP-A with 0 or 1.64 mM Ca(2+) in the subphase caused an aggregation of dark domains into a loose network, and the total amount of dark phase was increased to approximately 25% between pi of 10-28 mN/m. Monolayer features in the presence of 5 mM Ca(2+) and SP-A were not substantially different from those spread in the absence of SP-A, likely due to a self-association and aggregation of SP-A in the presence of higher concentrations of Ca(2+). PSLE films were spread on a subphase containing 0.16 microg/ml SP-A with covalently bound Texas Red (TR-SP-A). In the absence of Ca(2+), TR-SP-A associated with the reorganized dark phase (as seen with the lipid probe). The presence of 5 mM Ca(2+) resulted in an appearance of TR-SP-A in the fluid phase and of aggregates at the fluid/gel phase boundaries of the monolayers. This study suggests that SP-A associates with PSLE monolayers, particularly with condensed or solid phase lipid, and results in some reorganization of rigid phase lipid in surfactant monolayers.     

Genetic variation in cultivated strains of <Emphasis Type="Italic">Agaricus blazei</Emphasis>

Genetic differences among Agaricus blazei strains were investigated using somatic incompatibility testing, isozyme analysis, restriction fragment length polymorphism (RFLP) analysis of mitochondrial DNA (mtDNA), and random amplified polymorphic DNA (RAPD) analysis. Eight strains, one cultivated strain from Brazil and seven from Japan, were used in this study. Somatic incompatibility interactions were observed between the Brazilian cultivated strain and the Japanese strains. The Brazilian cultivated strain had its own distinct patterns of esterase isozyme and mtDNA RFLP, but all seven Japanese cultivated strains showed identical patterns. When the RAPD patterns, obtained using eight primers, were compared the eight strains had their own distinct RAPD profiles. Distance values were calculated between all pairs of the strains based on presence or absence of individual RAPD bands, and a dendrogram was constructed by unweighted pair-group method with arithmetic clustering (UPGMA) analysis. Seven Japanese cultivated strains were grouped to each other, and this group was finally linked to the Brazilian cultivated strain. Based on these results, the degree of genetic variation among the A. blazei strains used is discussed.