Space use and genetic structure do not maintain color polymorphism in a species with alternative behavioral strategies

Space use including territoriality and spatial arrangement within a population can reveal important information on the nature, dynamics, and evolutionary maintenance of alternative strategies in color polymorphic species. Despite the prevalence of color polymorphic species as model systems in evolutionary biology, the interaction between space use and genetic structuring of morphs within populations has rarely been examined. Here, we assess the spatial and genetic structure of male throat color morphs within a population of the tawny dragon lizard, Ctenophorus decresii. Male color morphs do not differ in morphology but differ in aggressive and antipredator behaviors as well as androgen levels. Despite these behavioral and endocrine differences, we find that color morphs do not differ in territory size, with their spatial arrangement being essentially random with respect to each other. There were no differences in genetic diversity or relatedness between morphs; however, there was significant, albeit weak, genetic differentiation between morphs, which was unrelated to geographic distance between individuals. Our results indicate potential weak barriers to gene flow between some morphs, potentially due to nonrandom pre‐ or postcopulatory mate choice or postzygotic genetic incompatibilities. However, space use, spatial structure, and nonrandom mating do not appear to be primary mechanisms maintaining color polymorphism in this system, highlighting the complexity and variation in alternative strategies associated with color polymorphism.     

Growth inhibition of metronidazole-susceptible and metronidazole-resistant strains of Gardnerella vaginalis by Lactobacilli in vitro.

Metronidazole resistance was produced in susceptible Gardnerella vaginalis after subculture in the presence of metronidazole. Metronidazole-resistant gardnerellae were less susceptible to growth inhibition by Lactobacillus culture filtrates. A low pH (+/- 4) and lactic acid accounted for 60 to 95% of inhibitory activity, and H2O2 accounted for only 0 to 30%. However, in the presence of myeloperoxidase, H2O2-producing lactobacilli decreased the viability of metronidazole-susceptible gardnerellae 2,000-fold.     

Neurofilament Protein Phosphorylation in Spinal Cord of Experimentally Diabetic Rats

This study was designed to determine if the known decrease in slow axonal transport of proteins in the sciatic nerve of experimentally diabetic rats is related to altered phosphorylation of neurofilament proteins (NFPs). Rats were rendered diabetic with 50 mg/kg of streptozotocin, i.p. At 3 and 6 weeks later, NFPs were prepared from spinal cord. The in vivo phosphorylation state of NFPs was examined by using phosphate-dependent (RT97) and -independent (RMd09) antibodies against high-molecular-mass NFPs on Western blots. Neurofilament-associated kinase activity was also measured in vitro by incubation of NFPs with [32P]ATP. Phosphorylation of all three NFPs (high, medium, and low molecular mass) occurred, as confirmed by gel electrophoresis and autoradiography. At 30 min of incubation, protein-bound radioactivity in NFPs from diabetic animals was reduced to 86.7 +/- 3.4 and 54.3 +/- 19.6% of that in nondiabetic animals at 3 and 6 weeks of diabetes, respectively (p less than 0.001 and p less than 0.05, respectively). NFPs were also incubated with acid phosphatase and rephosphorylated. Results showed that the increased in vivo phosphorylation contributed to the decreased in vitro phosphorylation. Extraction of protein kinases and addition back to the NFPs revealed, in addition, a reduced activity in the diabetic animals of the protein kinases measured in vitro.     

Regulation of pathways of glucose metabolism in kidney. The effect of experimental diabetes on the activity of the pentose phosphate pathway and the glucuronate-xylulose pathway.

Measurements have been made of the activities of enzymes of the pentose phosphate pathway, the glucuronate-xylulose pathway, hexokinase and phosphofructokinase in kidney of diabetic and normal rats. The activities of these enzymes keep pace with kidney growth, remaining constant per gram tissue but showing a marked increase on the basis of total activity per 100 g body wt. The formation of ¹⁴CO₂ from [1-¹⁴C]glucose and [6-¹⁴C]glucose by kidney slices from diabetic rats was decreased to approximately half the control value; evidence was obtained for an equivalent dilution of the glucose 6-phosphate pool. Correction of the ¹⁴CO₂ yields for the change in specific activity of glucose 6-phosphate yielded values consistent with the enzyme profile. Calculations from specific yields of ¹⁴CO₂ provided evidence for an increased flux of glucose via the pentose phosphate pathway in the kidney in diabetes. The results are discussed in relation to kidney hypertrophy in diabetes and the requirement for ribose 5-phosphate and NADPH for biosynthetic reactions and in relation to the thickening of the basement membrane in diabetes. These results are in accord with the concept of glucose overutilization by non-insulin-requiring tissues.     

Interaction of lipoprotein lipase and apolipoprotein C-II with sonicated vesicles of 1,2-ditetradecylphosphatidylcholine: comparison of binding constants

The interaction of lipoprotein lipase (LpL) and its activator protein, apolipoprotein C-II (apoC-II), with a nonhydrolyzable phosphatidylcholine, 1,2-ditetradecyl-rac-glycero-3-phosphocholine (C14-ether-PC), was studied by fluorescence spectroscopy. A complex of 320 molecules of C14-ether-PC per LpL was isolated by density gradient ultracentrifugation in KBr. The intrinsic tryptophan fluorescence emission spectrum of LpL was shifted from 336 nm in the absence of lipid to 330 nm in the LpL-lipid complex; the shift was associated with a 40% increase in fluorescence intensity. Addition of C14-ether-PC vesicles to apoC-II caused a 2.5-fold increase in intrinsic tryptophan fluorescence and a shift in emission maximum from 340 to 317 nm. LpL and apoC-II/C14-ether-PC stoichiometries and binding constants were determined by measuring the increase in the intrinsic tryptophan fluorescence as a function of lipid and protein concentrations; for LpL the rate and magnitude of the fluorescence increases were relatively independent of temperature in the range 4-37 degrees C. A stoichiometry of 270 PC per LpL for the LpL-lipid complex compares favorably with the value obtained in the isolated complex. The dissociation constant (Kd) of the complex is 4.3 X 10(-8) M. For apoC-II, the stoichiometry of the complex is 18 PC per apoprotein, and the Kd is 3.0 X 10(-6) M. These data suggest that LpL binds more strongly than apoC-II to phosphatidylcholine interfaces.     

Interaction of lipoprotein lipase with phospholipid vesicles: effect on protein and lipid structure

The interaction of lipoprotein lipase (LpL) and a nonhydrolyzable phosphatidylcholine, 1,2-ditetradecyl-rac-glycero-3-phosphocholine (C14-ether-PC), has been studied by several physical methods. Analysis of the circular dichroic spectrum of LpL gave the following fractional conformation: 35% alpha-helix, 30% beta-pleated sheet, and 45% remaining structure. No significant change in the circular dichroic spectrum of LpL was observed on addition of C14-ether-PC vesicles. The quenching of LpL fluorescence by acrylamide and iodide ion was decreased only slightly by addition of C14-ether-PC vesicles. Addition of LpL to sonicated C14-ether-PC vesicles containing entrapped carboxyfluorescein caused the release of less than 15% of the vesicle contents in 20 min, indicating that the enzyme did not disrupt the structure of the lipid. In contrast, greater than 80% of the vesicle contents were released with the addition of apolipoprotein A-I to an identical vesicle preparation. The temperature dependence of the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene incorporated into C14-ether-PC vesicles was not significantly altered by the addition of LpL. When LpL is added to vesicles, the bilayer structure of the vesicles is not disrupted as observed by freeze-fracture electron microscopy. However, at low ionic strength (0.1-0.25 M NaCl) significant aggregation of intact vesicles is observed by light scattering and electron microscopy. Vesicle aggregation is prevented and reversed by 1 M NaCl and by heparin. These data demonstrate that LpL binds to the surface of a lipid interface, without dramatic changes in lipid bilayer or protein structure.