Fecal excretion of intestinal glycosphingolipids by newborns and young children

Glycosphingolipids were shown to persist in human fecal excretions from birth up 2 years of age. The pattern of glycosphingolipids was dependent on blood group and secretor status of the child and changed dramatically during the first months of life. Perinatally cerebroside, hematoside and blood group active fucolipids were dominating among fecal glycolipids. From the time of weaning lactosylceramide abruptly became and then persisted as a dominating glycolipid although cerebroside, complex gangliosides and blood group active fucolipids could still be detected in feces even at 2 years of age.     

Blood to brain transport after newborn cerebral ischemia/reperfusion injury

These experiments examine the transfer of urea, sodium, and sucrose from blood to brain in an animal model of newborn cerebral ischemia-reperfusion injury. Cerebral ischemia (20 min) was produced in anesthetized, ventilated piglets by increasing intracranial pressure above mean arterial blood pressure, thereby reducing cerebral perfusion pressure to zero. The blood to brain transfer of urea, sodium, and sucrose was then measured in sham control piglets and at 30 min and 2 hr of reperfusion following ischemia. At 30 min of reperfusion, urea and sodium transfer were increased while sucrose transfer was unchanged. However, at 2 hr of reperfusion, transfer of all three tracers was elevated. The difference in the time course of increased transport of these substances into the brain following ischemia cannot be explained by size differences, indicating that changes in the blood-brain barrier following ischemia are more complex than merely opening junctions between cells and creating leaky sites. Alterations in blood-brain barrier transport could participate in altered neuronal function after ischemia-reperfusion injury.     

Growth of Clostridium perfringens in cooked chili during cooling.

U.S. Department of Agriculture regulations require that brick chili be cooled from 48.9 degrees C to 4.4 degrees C within 2 h of cooking, but processors may not always be able to comply. Studies were conducted to evaluate the extent of bacterial multiplication resulting from outgrowth of germinated Clostridium perfringens spores experimentally inoculated into chili and incubated at various temperatures. Inoculated samples were heated (75 degrees C for 20 min) to activate spores, quickly equilibrated, and held at one of five desired temperatures for 6 h. No growth was observed for C. perfringens in samples held at 26.7 degrees C and below for 6 h, but growth was observed by 6 h in samples held at 32.2 degrees C and after 2 h in samples held at temperatures between 37.8 degrees C and 48.9 degrees C. Using isothermal growth data, we developed a simple model for predicting the growth of bacteria with time under exponential cooling conditions. The model predicts both the lag phase and the numbers of bacteria at specific times during the growth phase. It was developed by using isothermal growth data and tested by using temperature-varying growth data from experiments with spores of C. perfringens in chili. Actual data agreed closely with predicted results. The results should be useful for evaluating the hazard potential for growth of C. perfringens in chili.     

Chemotaxis in the Marine Fungus Rhizophydium littoreum

Zoospores of the marine chytrid Rhizophydium littoreum are attracted to a variety of substances common to their environment. In general, carbohydrates and polysaccharides elicited strong concentration-dependent positive responses. There was no direct correlation between all substances used as foods and those stimulating positive responses. The chemotactic activities of this organism should, however, tend to bring it toward concentrated food sources.     

Sequence and specificity of a soluble lactose-binding lectin from Xenopus laevis skin.

A 16-kDa lactose-binding lectin comprises 5% or more of the soluble protein in Xenopus laevis skin. This lectin is mainly localized in the cytoplasm of granular gland cells. In response to stress, the lectin along with a variety of toxic and antibiotic peptides are released onto the skin surface by holocrine secretion. We have purified the lectin, sequenced tryptic peptides using tandem mass spectrometry and Edman degradation, and isolated full-length cDNA using a deduced oligonucleotide. Comparison of the cDNA and peptide sequences revealed expression of at least two isolectins, which differ in sequence at only two or three amino acids. Comparison of cDNA with complementary message by ribonuclease protection confirmed expression in approximately equal abundance of two nearly identical messages. The major soluble lactose-binding lectin expressed in Xenopus muscle is composed of these same isolectins, but at 100-fold lower levels. Similarities and distinctions in sequence and carbohydrate-binding specificity indicate that this lectin is a novel member of a family of soluble lactose-binding lectins expressed in a wide range of vertebrate tissues.     

Delayed herbivory by migratory geese increases summer‐long CO2 uptake in coastal western Alaska

The advancement of spring and the differential ability of organisms to respond to changes in plant phenology may lead to “phenological mismatches” as a result of climate change. One potential for considerable mismatch is between migratory birds and food availability in northern breeding ranges, and these mismatches may have consequences for ecosystem function. We conducted a three‐year experiment to examine the consequences for CO₂ exchange of advanced spring green‐up and altered timing of grazing by migratory Pacific black brant in a coastal wetland in western Alaska. Experimental treatments represent the variation in green‐up and timing of peak grazing intensity that currently exists in the system. Delayed grazing resulted in greater net ecosystem exchange (NEE) and gross primary productivity (GPP), while early grazing reduced CO₂ uptake with the potential of causing net ecosystem carbon (C) loss in late spring and early summer. Conversely, advancing the growing season only influenced ecosystem respiration (ER), resulting in a small increase in ER with no concomitant impact on GPP or NEE. The experimental treatment that represents the most likely future, with green‐up advancing more rapidly than arrival of migratory geese, results in NEE changing by 1.2 µmol m^?2 s^?1 toward a greater CO₂ sink in spring and summer. Increased sink strength, however, may be mitigated by early arrival of migratory geese, which would reduce CO₂ uptake. Importantly, while the direct effect of climate warming on phenology of green‐up has a minimal influence on NEE, the indirect effect of climate warming manifest through changes in the timing of peak grazing can have a significant impact on C balance in northern coastal wetlands. Furthermore, processes influencing the timing of goose migration in the winter range can significantly influence ecosystem function in summer habitats.     

How does a small molecule bind at a cryptic binding site?

Protein-protein interactions (PPIs) are ubiquitous biomolecular processes that are central to virtually all aspects of cellular function. Identifying small molecules that modulate specific disease-related PPIs is a strategy with enormous promise for drug discovery. The design of drugs to disrupt PPIs is challenging, however, because many potential drug-binding sites at PPI interfaces are “cryptic”: When unoccupied by a ligand, cryptic sites are often flat and featureless, and thus not readily recognizable in crystal structures, with the geometric and chemical characteristics of typical small-molecule binding sites only emerging upon ligand binding. The rational design of small molecules to inhibit specific PPIs would benefit from a better understanding of how such molecules bind at PPI interfaces. To this end, we have conducted unbiased, all-atom MD simulations of the binding of four small-molecule inhibitors (SP4206 and three SP4206 analogs) to interleukin 2 (IL2)—which performs its function by forming a PPI with its receptor—without incorporating any prior structural information about the ligands’ binding. In multiple binding events, a small molecule settled into a stable binding pose at the PPI interface of IL2, resulting in a protein–small-molecule binding site and pose virtually identical to that observed in an existing crystal structure of the IL2-SP4206 complex. Binding of the small molecule stabilized the IL2 binding groove, which when the small molecule was not bound emerged only transiently and incompletely. Moreover, free energy perturbation (FEP) calculations successfully distinguished between the native and non-native IL2–small-molecule binding poses found in the simulations, suggesting that binding simulations in combination with FEP may provide an effective tool for identifying cryptic binding sites and determining the binding poses of small molecules designed to disrupt PPI interfaces by binding to such sites.     

Macrophage inflammatory protein-2 is required for neutrophil passage across the epithelial barrier of the infected urinary tract

IL-8 is a major human neutrophil chemoattractant at mucosal infection sites. This study examined the C-X-C chemokine response to mucosal infection, and, specifically, the role of macrophage inflammatory protein (MIP)-2, one of the mouse IL-8 equivalents, for neutrophil-epithelial interactions. Following intravesical Escherichia coli infection, several C-X-C chemokines were secreted into the urine, but only MIP-2 concentrations correlated to neutrophil numbers. Tissue quantitation demonstrated that kidney MIP-2 production was triggered by infection, and immunohistochemistry identified the kidney epithelium as a main source of MIP-2. Treatment with anti-MIP-2 Ab reduced the urine neutrophil numbers, but the mice had normal tissue neutrophil levels. By immunohistochemistry, the neutrophils were found in aggregates under the pelvic epithelium, but in control mice the neutrophils crossed the urothelium into the urine. The results demonstrate that different chemokines direct neutrophil migration from the bloodstream to the lamina propria and across the epithelium and that MIP-2 serves the latter function. These findings suggest that neutrophils cross epithelial cell barriers in a highly regulated manner in response to chemokines elaborated at this site. This is yet another mechanism that defines the mucosal compartment and differentiates the local from the systemic host response.     

Introduction to galectins

Good evidence suggest roles of galectins in cancer, immunity and inflammation, and development, but a unifying picture of their biological function is lacking. Instead galectins appear to have a particularly diverse, bewildering but intriguing array of activities both inside and outside cells--"clear truths and mysteries are inextricably twined". Fortunately this has not discouraged but rather enthused a large number of good galectin researchers, some of which have contributed to this special issue of Glycoconjugate Journal to provide a personal, critical status of the field. Here we will give a brief introduction to the galectins as a protein family with some comments on nomenclature.