Effect of mixed diets (cyanobacteria and green algae) on the population growth of the cladocerans <Emphasis Type="Italic">Ceriodaphnia dubia</Emphasis> and <Emphasis Type="Italic">Moina macrocopa</Emphasis>

Microcystis aeruginosa, a cosmopolitan form, is a colonial cyanobacterium, which is also common in many freshwater bodies in Mexico. In eutrophic water bodies cyanobacteria are often the main phytoplankton that co-exist with cladocerans. We evaluated the effect of mixed diets, comprising 0, 25, 50, 75, and 100% on dry weight basis of M. aeruginosa, and the rest of one of two green algal species (Chlorella vulgaris and Scenedesmus acutus), on the population growth of the cladocerans Ceriodaphnia dubia and Moina macrocopa. Regardless of the share of M. aeruginosa in the mixed diet, C. dubia fed Chlorella had a longer initial lag phase. However, in mixed diet with S. acutus, the lag phase of C. dubia increased with increasing proportion of M. aeruginosa. When raised on 100% M. aeruginosa, the population growth of C. dubia was lowered compared with 100% S. acutus or 100% C. vulgaris. Increased proportion of M. aeruginosa in the mixed diet also resulted in decreased abundance of M. macrocopa. Irrespective of diet type, M. macrocopa had a shorter lag phase than C. dubia. Depending on the diet type, the rate of population increase (r) of C. dubia varied from 0.07 to 0.26 d⁻¹ while that of M. macrocopa was higher (0.14–0.61 d⁻¹). For both cladoceran species, the lower r values were obtained when fed Microcystis. Our study showed that the strain of M. aeruginosa was not highly toxic to cause total elimination of either C. dubia or M. macrocopa. Addition of a green algal component to the diet improved the population growth rates of both cladoceran species.     

Role of hydrogen peroxide during the interaction between the hemibiotrophic fungal pathogen Septoria tritici and wheat

Hydrogen peroxide (H(2)O(2)) is reported to inhibit biotrophic but benefit necrotrophic pathogens. Infection by necrotrophs can result in a massive accumulation of H(2)O(2) in hosts. Little is known of how pathogens with both growth types are affected (hemibiotrophs). The hemibiotroph, Septoria tritici, infecting wheat (Triticum aestivum) is inhibited by H(2)O(2) during the biotrophic phase, but a large H(2)O(2) accumulation occurs in the host during reproduction. Here, we infiltrated catalase, H(2)O(2) or water into wheat during the biotrophic or the necrotrophic phase of S. tritici and studied the effect of infection on host physiology to get an understanding of the survival strategy of the pathogen. H(2)O(2) removal by catalase at both early and late stages made plants more susceptible, whereas H(2)O(2) made them more resistant. H(2)O(2) is harmful to S. tritici throughout its life cycle, but it can be tolerated. The late accumulation of H(2)O(2) is unlikely to result from down-regulation of photosynthesis, but probably originates from damage to the peroxisomes during the general tissue collapse, which is accompanied by release of soluble sugars in a susceptible cultivar.     

Acute upregulation of hedgehog signaling in mice causes differential effects on cranial morphology

Hedgehog (HH) signaling, and particularly signaling by sonic hedgehog (SHH), is implicated in several essential activities during morphogenesis, and its misexpression causes a number of developmental disorders in humans. In particular, a reduced mitogenic response of cerebellar granule cell precursors to SHH signaling in a mouse model for Down syndrome (DS), Ts65Dn, is substantially responsible for reduced cerebellar size. A single treatment of newborn trisomic mice with an agonist of the SHH pathway (SAG) normalizes cerebellar morphology and restores some cognitive deficits, suggesting a possible therapeutic application of SAG for treating the cognitive impairments of DS. Although the beneficial effects on the cerebellum are compelling, inappropriate activation of the HH pathway causes anomalies elsewhere in the head, particularly in the formation and patterning of the craniofacial skeleton. To determine whether an acute treatment of SAG has an effect on craniofacial morphology, we quantitatively analyzed the cranial form of adult euploid and Ts65Dn mice that were injected with either SAG or vehicle at birth. We found significant deformation of adult craniofacial shape in some animals that had received SAG at birth. The most pronounced differences between the treated and untreated mice were in the midline structures of the facial skeleton. The SAG-driven craniofacial dysmorphogenesis was dose-dependent and possibly incompletely penetrant at lower concentrations. Our findings illustrate that activation of HH signaling, even with an acute postnatal stimulation, can lead to localized dysmorphology of the skull by generating modular shape changes in the facial skeleton. These observations have important implications for translating HH-agonist-based treatments for DS.KEY WORDS: Hedgehog signaling, Craniofacial shape, Down syndrome, Geometric morphometrics     

Side chain SAR of bicyclic β-lactamase inhibitors (BLIs). 1. Discovery of a class C BLI for combination with imipinem

Bridged monobactam β-lactamase inhibitors were prepared and evaluated as potential partners for combination with imipenem to overcome class C β-lactamase mediated resistance. The (S)-azepine analog 2 was found to be effective in both in vitro and in vivo assays and was selected for preclinical development.     

Diabetes results in structural alteration of chondroitin sulfate/dermatan sulfate in the rat kidney: effects on the binding to extracellular matrix components

Chondroitin sulfate (CS)/dermatan sulfate (DS) is a group of sulfated polymers, which play an essential role in various biological phenomena. In the kidney, they are present in small but significant amounts. Studies on their structure-function relationship in the kidney and their changes during diabetic conditions have not been rigorously looked into, which is the focus of this paper. The CS/DS content decreased significantly (14%) during diabetic conditions. This was accompanied by a decrease in the CS/heparan sulfate ratio. Disaccharide composition analysis revealed fine structural changes especially with respect to the E unit [glucuronic acid β1-3 N-acetyl d-galactosamine (4,6-O-sulfate)] and the degree of sulfation. The mRNA expression levels of major enzymes involved in the synthesis of the "E"-disaccharide unit showed a decrease during diabetes. The changes in CS/DS had implications on ligand-binding properties when tested in vitro for binding to major extracellular matrix (ECM) components such as type IV collagen, laminin and fibronectin. Thus, this study provides insights into the structure-function relationship of CS/DS in the kidney during diabetes and alterations of which could aggravate conditions such as diabetic nephropathy by virtue of them being a part of ECM components.     

Structural characterization of N-linked oligosaccharides of laminin from rat kidney: changes during diabetes and modulation by dietary fiber and butyric acid

Carbohydrates of laminin, a family of large multidomain glycoproteins, have been implicated in various cellular activities including maintaining the protein structure, its function and also basement membrane integrity. During the course of our investigation, we observed that purified laminin from kidneys of control, diabetic, and dietary fiber- and butyric acid-treated diabetic rats showed differences in binding to extracellular matrix components. This prompted us to determine whether there are structural changes in laminin oligosaccharides. In this study, we have characterized a few major N-linked oligosaccharides isolated from purified laminin in various experimental groups, viz. normal, diabetic and diabetic rats fed with dietary fiber and butyric acid. Sugar composition, as identified by GLC, revealed the presence of mannose, galactose and N-acetylglucosamine. In order to study fine structures of the oligosaccharides, N-linked oligosaccharides of laminin were released by Peptide-N-glycosidase F digestion, end-labeled with 2-anthranilic acid and fractionated by lectin affinity chromatography. Furthermore, structural elucidation carried out by MALDI-TOF MS/MS analysis showed variations in the oligosaccharide sequence of laminin during diabetes which were altered by the feeding of dietary fiber and butyric acid.     

Categorization of environmental sounds

Sounds in the natural environment are non-stationary, in that their spectral dynamics is time-dependent. We develop measures to analyze the spectral dynamics of environmental sound signals and find that they fall into two categories—simple sounds with slowly varying spectral dynamics and complex sounds with rapidly varying spectral dynamics. Based on our results and those from auditory processing we suggest rate of spectral dynamics as a possible scheme to categorize sound signals in the environment.