Plant size, latitude, and phylogeny explain within-population variability in herbivory.

Interactions between plants and herbivores are central in most ecosystems, but their strength is highly variable. The amount of variability within a system is thought to influence most aspects of plant-herbivore biology, from ecological stability to plant defense evolution. Our understanding of what influences variability, however, is limited by sparse data. We collected standardized surveys of herbivory for 503 plant species at 790 sites across 116° of latitude. With these data, we show that within-population variability in herbivory increases with latitude, decreases with plant size, and is phylogenetically structured. Differences in the magnitude of variability are thus central to how plant-herbivore biology varies across macroscale gradients. We argue that increased focus on interaction variability will advance understanding of patterns of life on Earth.

Congenital renal anomalies in cloacal exstrophy: Is there a difference?

INTRODUCTION: Cloacal exstrophy (CE) is the most severe manifestation of the epispadias-exstrophy spectrum. Previous studies have indicated an increased rate of renal anomalies in children with classic bladder exstrophy (CBE). Given the increased severity of the CE defect, it was hypothesized that there would be an even greater incidence among these children. OBJECTIVE: The primary objective was to characterize renal anatomy in CE patients. Two secondary objectives were to compare these renal anatomic findings in male and female patients, and female patients with and without Müllerian anomalies. STUDY DESIGN: An Institutional Review Board-approved retrospective review of 75 patients from an institutional exstrophy database. Data points included: age at analysis, sex, and renal and Müllerian anatomy. Abnormal renal anatomy was defined as a solitary kidney, malrotation, renal ectopia, congenital cysts, duplication, and/or proven obstruction. Abnormal Müllerian anatomy was defined as uterine or vaginal duplication, obstruction, and/or absence. RESULTS: The Summary Table presents demographic data and renal anomalies. Males were more likely to have renal anomalies. Müllerian anomalies were present in 65.7% of female patients. Girls with abnormal Müllerian anatomy were 10 times more likely to have renal anomalies than those with normal Müllerian anatomy (95% CI 1.1-91.4, P = 0.027). DISCUSSION: Patients with CE had a much higher rate of renal anomalies than that reported for CBE. Males and females with Müllerian anomalies were at greater risk than females with normal uterine structures. Mesonephric and Müllerian duct interaction is required for uterine structures to develop normally. It has been proposed that women with both Müllerian and renal anomalies be classified separately from other uterine malformations on an embryonic basis. In these patients, an absent or dysfunctional mesonephric duct has been implicated as potentially causal. This provided an embryonic explanation for uterine anomalies in female CE patients. There were also clinical implications. Women with renal agenesis and uterine anomalies were more likely to have endometriosis than those with isolated uterine anomalies, but were also more likely to have successful pregnancies. Males may have had an analogous condition with renal agenesis and seminal vesicle cysts. Future research into long-term kidney function in this population, uterine function, and possible male sexual duct malformation is warranted. CONCLUSION: Congenital renal anomalies occurred frequently in children with CE. They were more common in boys than in girls. Girls with abnormal Müllerian anatomy were more likely to have anomalous renal development. Mesonephric duct dysfunction may be embyologically responsible for both renal and Müllerian maldevelopment.

Measuring tolerance to herbivory: accuracy and precision of estimates made using natural versus imposed damage.

Tolerance to herbivory (the ability of a plant to incur herbivore damage without a corresponding reduction in fitness) can be measured using either naturally occurring or imposed herbivore damage. After briefly reviewing some of the advantages and disadvantages of these approaches, we present calculations describing the degree to which estimates of tolerance will be biased by environmental variables that affect both herbivory and fitness. With naturally occurring herbivory the presence of environmental variables that are correlated with herbivory and fitness will result in biased estimates of tolerance. In contrast, estimates obtained from experiments in which herbivory is artificially imposed will be unbiased; however, under a wide range of parameter values these estimates will be less precise than estimates obtained from experiments in which herbivory is not manipulated.

Climate change is affecting altitudinal migrants and hibernating species.

Calendar date of the beginning of the growing season at high altitude in the Colorado Rocky Mountains is variable but has not changed significantly over the past 25 years. This result differs from growing evidence from low altitudes that climate change is resulting in a longer growing season, earlier migrations, and earlier reproduction in a variety of taxa. At our study site, the beginning of the growing season is controlled by melting of the previous winter's snowpack. Despite a trend for warmer spring temperatures the average date of snowmelt has not changed, perhaps because of the trend for increased winter precipitation. This disjunction between phenology at low and high altitudes may create problems for species, such as many birds, that migrate over altitudinal gradients. We present data indicating that this already may be true for American robins, which are arriving 14 days earlier than they did in 1981; the interval between arrival date and the first date of bare ground has grown by 18 days. We also report evidence for an effect of climate change on hibernation behavior; yellow-bellied marmots are emerging 38 days earlier than 23 years ago, apparently in response to warmer spring air temperatures. Migrants and hibernators may experience problems as a consequence of these changes in phenology, which may be exacerbated if climate models are correct in their predictions of increased winter snowfall in our study area. The trends we report for earlier formation of permanent snowpack and for a longer period of snow cover also have implications for hibernating species.

Inhibition of active oxygen generation in guinea-pig neutrophils by biscoclaurine alkaloids.

Effect of biscoclaurine alkaloids, such as cepharanthine, on active oxygen production of neutrophils was investigated. Cepharanthine inhibited both superoxide generation and luminol-dependent chemiluminescence (CL) induced by either formylmethionyl-leucyl-phenylalanine, opsonized zymosan, arachidonic acid or by phorbol myristate acetate. Ca2(+)- and phospholipid-dependent protein kinase (PKC) activity and the phosphorylation of cytoplasmic protein including 47 kDa proteins of neutrophils were also inhibited by cepharanthine; dose dependent inhibition of CL was quite similar to that of PKC. Among various biscoclaurines tested, the inhibitory effect of cepharanthine, tetrandrine and isotetrandrine was strong, but that of berbamine and cycreanine was weak; the inhibitory action of the former on lipid peroxidation and platelet aggregation were also stronger than those of the latter. These and other observations indicated that these alkaloids inhibited the active oxygen generation by way of stabilizing plasma membrane and inhibiting PKC and NADPH oxidase activation.

Changes in mitochondrial function by lipid peroxidation and their inhibition by biscoclaurin alkaloid.

During in vitro investigation of changes in mitochondrial function accompanying lipid peroxidation, it was found that cepharanthine, a biscoclaurin alkaloid, protects against such change. Results obtained were as follows: (1) Fe2+ induces lipid peroxidation of isolated mitochondria, resulting in diminished oxidative phosphorylation. (2) This diminishment largely depends on deterioration of ion compartmentation of the membrane and an increase in latent ATPase activity. (3) The Fe2+-induced deterioration in ion compartmentation is inhibited by cepharanthine. (4) Cepharanthine inhibits the mitochondrial lipid peroxidation induced by Fe2+. (5) Cepharanthine inhibits the lipid peroxidation of soybean lecithin liposomes by 60Co-irradiation.

Inhibition by biscoclaurine alkaloid of lipid peroxidation in biological membranes.

Biscoclaurine-type alkaloids were examined for ability to act as membrane-stabilizing agents and to protect against lipid peroxidation and deterioration of biological membrane. The following results were obtained. Biscoclaurine-type alkaloids inhibit Fe2+-induced lipid peroxidation of biological membrane. Cepharanthine protects against decrease in membrane compartmentation due to Fe2+-induced lipid peroxidation. Peroxidation of membrane lipid causes decrease in membrane fluidity but cepharanthine protects against this decrease. These protective actions are structure specific. They are also biscoclaurine-type specific and do not apply to coclaurine-type alkaloids such as papaverine. Based on these findings, the biological action of the alkaloid is discussed relative to membrane-stabilizing action and protective action against leukopenia induced by X-ray irradiation or mitomycin treatment in cancer therapy.

Effect of chinoform on the function of biological membranes.

To investigate the mechanism by which the toxic effect of chinoform (5-chloro-7-iodo-8-quinolinol) develops, its action on the function of biological membranes was examined. Findings were: 1. Chinoform induced K+ release from red cells. This effect was increased by prior addition of Mg2+ and decreased by albumin, ruthenium red, or lanthanum chloride. 2. Chinoform induced K+ release from isolated rat liver mitochondria more effectively in the presence of Mg2+ or other bivalent cations, and a chinoform-Mg chelate was more effective than chinoform alone. The K+ release from mitochondria was protected by albumin and to a certain extent by lanthanum chloride. 3. The change in the ion permeability of mitochondrial membrane induced by chinoform in the presence of Mg2+ was accompanied by uncoupling of the oxidative phosphorylation. These results suggest that chinoform interacts with membranes more effectively as a metal chelate, producing conformational and functional changes in those membranes.

Influence of superoxide generating system, vitamin E, and superoxide dismutase on radiation consequences.

During studies of the mechanism by which hemolysis is induced in irradiated human erythrocytes in vitro, several inducements of membrane lipid peroxidation and protective effects of vitamin E (V.E) and superoxide dismutase (SOD) were investigated. Findings were: (1) Before hemolysis, K+ release from erythrocytes induced by radiation stimulated hemolysis but was inhibited by V.E or SOD. (2) Lipid peroxidation of mitochondria induced by Fe3+, ADP, and superoxide (O2-) generating system, and lipid peroxidation of microsome induced by O2- generating system, were also inhibited by V.E or SOD. (3) X-ray or 60Co gamma-ray radiation stimulated lipid peroxidation of liver homogenate, microsome, and liposome. Some of this peroxidation was inhibited by V.E. or SOD. These results suggest that O2- and/or OH formation by radiation induces membrane lipid peroxidation, which causes deterioration of membrane resulting in change of ion permeability and consequent hemolysis.

Effect of rifampicin derivatives on the ion compartmentation of biological membranes.

Based on the experimental results that 3-formyl rifamycin SV acts as an uncoupler in vitro on rat liver mitochondria, the effect of some rifampicin derivatives on the K+ and H+ compartmentation of biological membranes was examined to obtain a chemiosmotic hypothesis for oxidative phosphorylation. The K+ release from mitochondria was remarkably stimulated by 3-formyl rifamycin SV in accordance with uncoupling of the oxidative phosphorylation. 3-Formyl rifamycin SV also stimulated the K+ release from red blood cells, though its action was not as effective as in mitochondria. It can be suggested that 3-formyl rifamycin SV interacts with biological membranes, causing a change in permeability to ions, especially of K+ and H+ through the mitochondrial membrane, resulting in uncoupling of the oxidative phosphorylation.