Noninvasive monitoring of follicle development,ovulation, and corpus luteum formation in the marmoset monkey (Callithrix jacchus) by ultrasonography

This is the first paper to describe ovarian changes associated with follicular growth, ovulation, and corpus luteum (CL) formation as monitored by ultrasonography in a multiovular primate, the marmoset monkey (Callithrix jacchus). Examinations were carried out transabdominally on unsedated females using a 10 MHz probe. Cycles were monitored by plasma progesterone and controlled by administration of prostaglandin F2α (PGF). The reliability of ultrasound was validated by comparing findings with direct observation of the ovaries at laparotomy. In eight females, 25 follicles were counted, of which 92% were depicted correctly by ultrasound. Of 14 CLs in five females, number and position were confirmed at laparotomy for 78%. Ultrasound examinations of ovaries throughout the follicular and luteal phase were performed in eight cycles and related to plasma profiles of luteinizing hormone (LH) and progesterone. One of these cycles was anovulatory. In the remaining seven cycles, 19 follicles were considered ovulatory follicles since they were seen on consecutive days and found again as CLs. Growth of individual follicles was monitored by measurements of follicle diameter from day 7 onward. Disappearance of follicles or changes in echogenicity were noted between days 9 and 11, preventing further measurements. Mean follicle size increased from 2.1 mm (range 1.6 mm–2.7 mm) on day 7 to 3.2 mm (range 2.7 mm–4.0 mm) on the day last seen. With one exception, the day follicles were last seen by ultrasound was consistent with the day of the preovulatory LH surge (day 9–11). The postovulatory rise in progesterone occurred 1–2 days later (day 11–13). These findings suggest that the day of ovulation as observed by ultrasound was characterized by either disappearance of follicles or increased follicular echogenicity. In conclusion, ultrasonography provides a reliable, noninvasive method for examinations of the ovarian cycle in the marmoset monkey. © 1996 Wiley-Liss, Inc.     

Effect of Nitrogen and Powdery Mildew on the Yield Formation of Two Winter Barley Cultivars1

In field experiments the effect of powdery mildew on the yield formation of two barley cultivars ‘Catinka’ (partially resistant) and ‘Tapir’ (susceptible) was investigated in relation to three levels of nitrogen fertilization (40, 90, 150 kg N/ha). Nitrogen increased especially the single ear yield of cv.‘Catinka’, whereas cv.‘Tapir’ showed symptoms of N oversupply. Infection density of Erysiphe graminis hordei also increased with increased nitrogen supply, although it decreased transiently, at the highest N level for cv.‘Tapir’. In general, cv.‘Catinka’ was less tolerant to infections with E. graminis than cv.‘Tapir’, but yield response of both cultivars to powdery mildew (17, 11 and 8 % and 12, 16, and 12 % yield losses for cv.,‘Catinka’ and ‘Tapir’. respectively) showed cultivar × nitrogen interrelationships. Starch and protein contents of grains indicated differences in the intensity of detrimental effects caused by powdery mildew limiting the formation of carbohydrates and/or the translocation processes. Regression analysis demonstrated a closer correlation of yield losses with the photosynthetically active leaf area (r =+0.96 and +0.93 for ‘Catinka’ and ‘Tapir’) than with disease intensity (r =−0.32 and −0.85). Theinte,rpretation of disease/yield loss relations and the detrimental effect of powdery mildew are discussed with reference to plant resistance, remaining green leaf area, the availability of nutrients, to ‘sink and source’ conditions and to the occurrence of,additional environmental stresses.     

Interactions of Fusarium species during prepenetration development

Interspecies interactions between Fusarium avenaceum, Fusarium culmorum, Fusarium graminearum, Fusarium poae, and Fusarium tricinctum were studied during early growth stages of isolates on model surfaces. Additionally, germination and germ tube growth of the pathogens were studied on attached and detached wheat leaves at 10 °C and 22 °C. Two-species interactions between Fusarium isolates during germination and germ tube growth were assessed after 8 hours of incubation. All species except F. tricinctum germinated and grew faster at higher than lower temperature. All species were able to germinate with more than one germ tube per conidium cell; and germination and germ tube growth were faster on leaves than on glass surface. Interactions among Fusarium species during germination and germ tube growth were predominantly competitive with macroconidia-producing species being more competitive. It is concluded that the type of conidia as well as environmental factors influence the competitiveness of Fusarium species during early stages of growth.     

Inhibition of 5-lipoxygenase by U73122 is due to covalent binding to cysteine 416

U73122 which was originally identified as a phospholipase C inhibitor represents a potent direct inhibitor of purified 5-lipoxygenase (5-LO) with an IC50 value of 30 nM. 5-LO catalyzes the conversion of arachidonic acid (AA) into leukotrienes which represent mediators involved in inflammatory and allergic reactions and in host defense reactions against microorganisms. Since the efficient inhibition of the human 5-LO enzyme depended on the thiol reactivity of the maleinimide group of U73122, we used this property to identify cysteine residues in the 5-LO protein that are important for 5-LO inhibition by U73122. We found by MALDI-MS that U73122 covalently binds to cysteine residues 99, 159, 248, 264, 416 and 449. Mutation of Cys416 to serine strongly reduces inhibition of 5-LO by U73122 and the additional mutation of three cysteines close to Cys416 further impairs 5-LO inhibition by the compound. Wash out experiments with U73122 and 5-LO indicated an irreversible binding of U73122. Together, our data suggest that the area around Cys416 which is close to the proposed AA entry channel to the active site is an interesting target for the development of new 5-LO inhibitors.     

Microbiological and SYBR green real-time PCR detection of major Fusarium head blight pathogens on wheat ears

Fusarium head blight (FHB) caused by several Fusarium species is one of the most serious diseases affecting wheat throughout the world. The efficiency of microbiological assays and real-time PCRto quantify major FHB pathogens in wheat ears after inoculation with F. graminearum, F. culmorum, F. avenaceum and F. poae undergreenhouse and field conditions were evaluated. The frequency of infected kernel, content of fungal biomass, disease severity and kernel weight were determined. To measure the fungal biomass an improved DNA extraction method and a SYBR Green real-time PCR were developed. The SYBR Green real-time PCR proved to be highly specific for individual detection of the species in a matrix including fungal and plant DNA. The effect of Fusarium infection on visible FHB severity, frequency of infected kernels and thousand-kernel mass (TKM) significantly depended on the Fusarium species/isolate. F. graminearum resulted in highest disease level, frequency of infected kernels, content of fungal biomass, and TKM reduction followed by F. culmorum, EF avenaceum and F. poae, respectively. The comparison of frequency and intensity of kernel colonization proved differences in aggressiveness and development of the fungi in the kernels. Only for F. graminearum, the most aggressive isolate, application of microbiological and real-time PCR assays gave similar results. For the other species, the intensity of kernel colonization was lower than expected from the frequency of infection.     

Biosynthesis of tetrahydrofolate in plants: crystal structure of 7,8-dihydroneopterin aldolase from Arabidopsis thaliana reveals a novel adolase class

Dihydroneopterin aldolase (DHNA) catalyses a retroaldol reaction yielding 6-hydroxymethyl-7,8-dihydropterin, a biosynthetic precursor of the vitamin, tetrahydrofolate. The enzyme is a potential target for antimicrobial and anti-parasite chemotherapy. A gene specifying a dihydroneopterin aldolase from Arabidopsis thaliana was expressed in a recombinant Escherichia coli strain. The recombinant protein was purified to apparent homogeneity and crystallised using polyethylenglycol as the precipitating agent. The crystal structure was solved by X-ray diffraction analysis at 2.2 Å resolution. The enzyme forms a D₄-symmetric homooctamer. Each polypeptide chain is folded into a single domain comprising an antiparallel four-stranded β-sheet and two long α-helices. Four monomers are arranged in a tetrameric ring, and two of these rings form a hollow cylinder. Well defined purine derivatives are found at all eight topologically equivalent active sites. The subunit fold of the enzyme is related to substructures of dihydroneopterin triphosphate epimerase, GTP cyclohydrolase I, and pyruvoyltetrahydropterin synthase, which are all involved in the biosynthesis of pteridine type cofactors, and to urate oxidase, although some members of that superfamily have no detectable sequence similarity. Due to structural and mechanistical differences of DHNA in comparison with class I and class II aldolases, a new aldolase class is proposed.     

Characterisation of<Emphasis Type="Italic">fusarium graminearum</Emphasis> and<Emphasis Type="Italic">F. culmorum</Emphasis> isolates by mycotoxin production and aggressiveness to wheat

A total of 27Fusarium culmorum isolates from Germany and 41F. graminearum isolates from Kenya were investigated for aggressiveness and mycotoxin production on wheat ears. In addition, ergosterol content of the kernels from ears inoculated withF. graminearum was determined and theF. culmorum isolates were tested for mycotoxin productionin vitro. For both pathogens, isolates markedly differed in aggressiveness. 59% and 37% of theF. culmorum isolates produced NIV and DON, respectively,in vivo andin vitro. The DON-producing isolates also produced 3-acDONin vitro. The more aggressive isolates produced mainly DON while the less aggressive isolates produced mainly NIV. 12% and 85% of theF. graminearum isolates produced NIV and DON, respectively. The highly aggressive isolates produced higher amounts of DON, aggressiveness being highly correlated to DON content in the kernels. NIV-producing isolates were less aggressive. Ergosterol content of kernels was moderately correlated to aggressiveness but highly correlated to DON content. Disease severity was associated with kernel weight reduction.     

Biophysical Controls on Community Succession in Stream Biofilms

Biofilm formation is controlled by an array of coupled physical, chemical, and biotic processes. Despite the ecological relevance of microbial biofilms, their community formation and succession remain poorly understood. We investigated the effect of flow velocity, as the major physical force in stream ecosystems, on biofilm community succession (as continuous shifts in community composition) in microcosms under laminar, intermediate, and turbulent flow. Flow clearly shaped the development of biofilm architecture and community composition, as revealed by microscopic investigation, denaturing gradient gel electrophoresis (DGGE) analysis, and sequencing. While biofilm growth patterns were undirected under laminar flow, they were clearly directed into ridges and conspicuous streamers under turbulent flow. A total of 51 biofilm DGGE bands were detected; the average number ranged from 13 to 16. Successional trajectories diverged from an initial community that was common in all flow treatments and increasingly converged as biofilms matured. We suggest that this developmental pattern was primarily driven by algae, which, as “ecosystem engineers,” modulate their microenvironment to create similar architectures and flow conditions in all treatments and thereby reduce the physical effect of flow on biofilms. Our results thus suggest a shift from a predominantly physical control to coupled biophysical controls on bacterial community succession in stream biofilms.