Conformational properties of the G.G mismatch in d(CGCGAATTGGCG)2 determined by NMR.

The conformational properties of the DNA duplex d(CGCGAATTGGCG)2, which contains two noncomplementary G.G base pairs, have been examined in aqueous solution by 1H and 31P NMR as a function of temperature. The G.G mismatch is highly destabilizing, with a Tm value 35 K below that observed for the native EcoRI dodecamer. The dodecamer appears symmetric in the NMR spectra and exists largely as an average B-type DNA conformation. However, the 1H and 31P NMR spectra give evidence of considerable conformational heterogeneity at the mismatched nucleotides and their nearest neighbors, which increases with increasing temperature. There is no evidence for a significant population of the syn purine conformation. The imino protons of the mispaired bases G4 and G9 are degenerate, resonate at high field, and exchange readily with solvent. These results indicate that the mispaired bases are only weakly hydrogen-bonded and are only partially stacked into the helix. On raising the temperature, the duplex shows increasing exchange between two or more conformations originating from the mismatch sites. However, these additional conformations maintain their Watson-Crick hydrogen bonding. The increase in chemical exchange is consistent with a quasimelting process for which the G.G sites provide local nuclei. Extensive modeling studies by dynamic annealing have confirmed that the G(anti).G(anti) conformation is favored and that the mispairs are poorly stacked within the helix. The results explain both the poor thermal stability and low hypochromicity of this duplex.     

Spawning habitat,behavior, and morphology as isolating mechanisms of the golden redhorse,Moxostoma erythrurum,and the black redhorse,M. duquesnei,two syntopic fishes

Synopsis Golden redhorse, Moxostoma erythrurum, and black redhorse, M. duquesnei, were observed spawning during the springs of 1984 through 1987 in Stony Creek, Illinois, at water temperatures ranging from 15–21°C. Both species spawned simultaneously within the same stream reach in 1987. Male golden redhorse aggressively defended territories on shoals and were joined by females from an adjacent pool. Black redhorse also spawned in riffles and displayed no agonistic behavior. Both species spawned throughout daylight hours in groups of two to five, and golden redhorse also spawned at night. Habitat utilization curves indicate that black redhorse spawned in habitat that was slightly deeper, much swifter, and over coarser substrate than that of the golden redhorse. Males of both species exhibited nuptial body color and breeding tubercles on anal and caudal fins, while only golden redhorse males had head tubercles. We suggest that these differences in spawning habitat, behavior, and morphology act as reproductive isolating mechanisms between the species and that the dichotomy in habitat and behavior may be due to competitive interactions.     

Ribeiroia Infection Is Not Responsible for Vermont Amphibian Deformities

Reports of limb deformities in amphibians have garnered wide notice from scientists and the public alike. Recent laboratory and field research has supported the hypothesis that infection by the helminth parasite, Ribeiroia ondatrae, is associated with deformities, particularly in the western United States. In this study, observational and experimental evidence from eastern United States (Vermont) provides evidence that Ribeiroia is absent from a large sample of sites including those with a history of relatively high frequencies of deformity, that the composition of deformities is distinct from that associated with experimental infection by Ribeiroia, and that the composition of limb deformities seen in natural populations in Vermont is typical of that reported in the literature. We suggest that while Ribeiroia has been shown to be responsible for deformities in some species and locations, other factors may be responsible where the composition of deformities is inconsistent with patterns resulting from known Ribeiroia infection.     

Expression of differentiated function by hepatocytes in primary culture: Variable effects of glucagon and insulin on gluconeogenesis during cell growth

Abstract. Hormonal effects on gluconeogenesis from lactate were studied during the growth cycle of adult rat parenchymal liver cells using a primary monolayer culture system previously described [25]. Basal and glucagon-stimulated gluconeogenic ability were found to decline rapidly during log phase, insulin-stimulated growth. A progressive recovery of gluconeogenic activity was observed after cell division subsided. Rates of lactate-gluconeogenesis were found also to decline in the absence of prior insulin exposure. This decline was not as rapid as the loss observed in cells cultured with insulin. However, in insulin-deficient cultures gluconeogenesis was completely abolished after 12 days and did not reelevate with further incubation unless cells were washed and exposed to glucagon. Decreasing growth rates of insulin-supplemented cultures by decreasing serum concentrations resulted in comparatively higher gluconeogenic activity.
The results presented here are consistent with previous observations of hepatic parenchymal expression of 'differentiated function' during cellular growth phases in culture (i.e., differentiated functions are generally lost during rapid growth and regained as cells become quiescent). The present study, however, presents unexpected effects of insulin on the apparent growth-state dependent gluconeogenic recovery. Our data imply that although insulin has long been known to inhibit gluconeogenesis, its presence in culture may facilitate long-term basal maintenance of gluconeogenic enzyme activity. Insulin also functions as a growth factor whose initial mitogenic effect correlates with decreased gluconeogenic function. These changes show no simple or predictive correlation with cyclic nucleotide metabolism.     

Three Minutes of All-Out Intermittent Exercise per Week Increases Skeletal Muscle Oxidative Capacity and Improves Cardiometabolic Health

We investigated whether a training protocol that involved 3 min of intense intermittent exercise per week — within a total training time commitment of 30 min including warm up and cool down — could increase skeletal muscle oxidative capacity and markers of health status. Overweight/obese but otherwise healthy men and women (n = 7 each; age  = 29±9 y; BMI  = 29.8±2.7 kg/m²) performed 18 training sessions over 6 wk on a cycle ergometer. Each session began with a 2 min warm-up at 50 W, followed by 3×20 s “all-out” sprints against 5.0% body mass (mean power output: ∼450–500 W) interspersed with 2 min of recovery at 50 W, followed by a 3 min cool-down at 50 W. Peak oxygen uptake increased by 12% after training (32.6±4.5 vs. 29.1±4.2 ml/kg/min) and resting mean arterial pressure decreased by 7% (78±10 vs. 83±10 mmHg), with no difference between groups (both p<0.01, main effects for time). Skeletal muscle biopsy samples obtained before and 72 h after training revealed increased maximal activity of citrate synthase and protein content of cytochrome oxidase 4 (p<0.01, main effect), while the maximal activity of β-hydroxy acyl CoA dehydrogenase increased in men only (p<0.05). Continuous glucose monitoring measured under standard dietary conditions before and 48–72 h following training revealed lower 24 h average blood glucose concentration in men following training (5.4±0.6 vs. 5.9±0.5 mmol/L, p<0.05), but not women (5.5±0.4 vs. 5.5±0.6 mmol/L). This was associated with a greater increase in GLUT4 protein content in men compared to women (138% vs. 23%, p<0.05). Short-term interval training using a 10 min protocol that involved only 1 min of hard exercise, 3x/wk, stimulated physiological changes linked to improved health in overweight adults. Despite the small sample size, potential sex-specific adaptations were apparent that warrant further investigation.     

Out of Alaska: morphological diversity within the genus <Emphasis Type="Italic">Eurytemora</Emphasis> from its ancestral Alaskan range (Crustacea,Copepoda)

The copepod genus Eurytemora occupies a wide range of habitat types throughout the Northern Hemisphere, with among the broadest salinity ranges of any known copepod. The epicenter of diversity for this genus lies along coastal Alaska, where several species are endemic. Systematic analysis has been difficult, however, because of a tendency toward morphological stasis in this genus, despite large genetic divergences among populations and species. The goals of this study were to (1) analyze patterns of morphological variation and divergence within this genus, focusing on Eurytemora species that occur in North America, and (2) determine patterns of geographic and salinity distribution of Eurytemora species within the ancestral range in Alaska. We applied a comparative multivariate morphological analysis using 16–26 characters from 125 specimens from 20 newly collected sites in Alaska and 15 existing samples predominantly from North America. Results from principal component and hierarchical cluster analyses identified seven distinct morphological species of Eurytemora in North America (E. affinis, E. americana, E. canadensis, E. composita, E. herdmani, E. pacifica, and E. raboti), and identified diagnostic characters that distinguish the species (forming the basis for a new identification key). Several previously named species were regarded as synonyms. The sites we sampled in Alaska were remarkable in the high levels of sympatry of Eurytemora species, to a degree not seen outside of Alaska. Future studies of Eurytemora should shed light on patterns of habitat invasions and physiological evolution within the genus, and yield insights into mechanisms leading to its remarkably broad geographic and habitat range.     

Suppressing Glucose Transporter Gene Expression in Schistosomes Impairs Parasite Feeding and Decreases Survival in the Mammalian Host

Adult schistosomes live in the host''s bloodstream where they import nutrients such as glucose across their body surface (the tegument). The parasite tegument is an unusual structure since it is enclosed not by the typical one but by two closely apposed lipid bilayers. Within the tegument two glucose importing proteins have been identified; these are schistosome glucose transporter (SGTP) 1 and 4. SGTP4 is present in the host interactive, apical tegumental membranes, while SGTP1 is found in the tegumental basal membrane (as well as in internal tissues). The SGTPs act by facilitated diffusion. To examine the importance of these proteins for the parasites, RNAi was employed to knock down expression of both SGTP genes in the schistosomula and adult worm life stages. Both qRT-PCR and western blotting analysis confirmed successful gene suppression. It was found that SGTP1 or SGTP4-suppressed parasites exhibit an impaired ability to import glucose compared to control worms. In addition, parasites with both SGTP1 and SGTP4 simultaneously suppressed showed a further reduction in capacity to import glucose compared to parasites with a single suppressed SGTP gene. Despite this debility, all suppressed parasites exhibited no phenotypic distinction compared to controls when cultured in rich medium. Following prolonged incubation in glucose-depleted medium however, significantly fewer SGTP-suppressed parasites survived. Finally, SGTP-suppressed parasites showed decreased viability in vivo following infection of experimental animals. These findings provide direct evidence for the importance of SGTP1 and SGTP4 for schistosomes in importing exogenous glucose and show that these proteins are important for normal parasite development in the mammalian host.     

Universal ecological patterns in college basketball communities

The rank abundance of common and rare species within ecological communities is remarkably consistent from the tropics to the tundra. This invariant patterning provides one of ecology's most enduring and unified tenets: most species rare and a few very common. Increasingly, attention is focused upon elucidating biological mechanisms that explain these species abundance distributions (SADs), but these evaluations remain controversial. We show that college basketball wins generate SADs just like those observed in ecological communities. Whereas college basketball wins are structured by competitive interactions, the result produces a SAD pattern indistinguishable from random wins. We also show that species abundance data for tropical trees exhibits a significant-digit pattern consistent with data derived from complex structuring forces. These results cast doubt upon the ability of SAD analysis to resolve ecological mechanism, and their patterning may reflect statistical artifact as much as biological processes.     

Pretreatment weight change is associated with obesity treatment outcomes

Clinical experience suggests some individuals begin obesity treatment weighing more than they did at pretreatment assessment. Weight fluctuations between baseline screening and the first treatment session were examined among individuals enrolling in a group behavioral obesity treatment outcome study. Participants (N = 480, 94% female; 28% African American; M BMI = 35.7) were classified into those who started treatment having gained weight (≥ +1.15% above screening weight), lost weight (≤ -1.15% below screening weight) or remained weight stable. The majority of participants were weight-stable (61%) during the waiting period, but 23% lost weight (-2.36 ± 1.26 kg) and 16% gained weight (+2.11 ± 1.04 kg) between baseline screening and initiating treatment. Those who lost during the pretreatment period went on to have the greatest losses at 6-months (-8.9 ± 4.9 kg), with significantly greater weight losses than either the weight-stable (-6.1 ± 5.8 kg) or the weight-gain (-5.7 ± 5.8 kg) groups. Further, those who lost weight during the waiting period went on to attend a significantly higher proportion of treatment sessions and submitted more self-monitoring diaries than those who gained weight and those who stayed weight stable while waiting. Thus, pretreatment weight change was associated with treatment outcomes and may be relevant for research screening. Further, pretreatment weight change may be a clinical marker for likely success in behavioral weight control and as such warrants additional investigation to inform potential methods for enhancing outcomes for individuals in obesity treatment.