Effect of increasing methanol concentrations on physiology and cytology ofCandida boidinii

Concentration of methanol in the medium strongly affected not only the physiology but also the cytology ofCandida boidinii strain 2 cells in a methanol-limited chemostat at a constant dilution rateD 0.1/h and at low pH 3.0. The formation of large cubic peroxisomes with high alcohol oxidase (AO) activity observed at low methanol concentration (S ₀ 3 g/L) disappeared on increasing the methanol concentration in the inflow medium. The AO activity in the cells sharply decreased, followed by accumulation of riboflavin phosphate and residual methanol in the medium. The activity of catalase was relatively stable. At methanol concentrationS ₀>K _I (K ₁ equal to 12 g methanol per L), which included a substantial increase in methanol dissimilation, documented by higher formaldehyde and formate dehydrogenase activities and by lower yield coefficient on methanol, the yeast cells contained large lobe-shaped peroxisomes and a smaller number of larger mitochondria. The cells formed pseudomycelium with a thick septum between the mother and daughter cells.     

The many faces of Peridinium cinctum (Peridiniaceae,Peridiniales): morphological and molecular variability in a common dinophyte

Peridinium cinctum is a common freshwater dinophyte with a long history of research. Erich Lindemann was the first to assess intraspecific variability in this species focusing on plate pattern variation. Since then, this issue has been neglected but with the application of DNA sequence diagnostics, a combination of morphological and molecular characters may enable taxonomic delimitations. Our aim was to identify distinct morphotypes using plate pattern as the main characteristic and then compare them to the geographic occurrence of particular ribotypes (as inferred from sequences of the Internal Transcribed Spacer: ITS) in samples from Central Europe. Approximately 200 observations were carried out under the inverse light microscope for each of a total of 15 strains. We observed two main variations from the abundant plate pattern in P. cinctum, namely an unusual position of the 2a plate and the irregular shape of the 1a plate. In 88 (predominantly clonal) strains, we identified five different ribotypes (submitted as 71 new GenBank entries) which had no clear correlation to the defined morphotypes and/or spatial occurrences. In four cases, we detected two distinct ribotypes at the same locality. However, samples collected south of the Danube River presented a different predominant morphotype from the rest of the samples, thus implying a potential biogeographic signal as inferred from morphology. In general, there is morphological and molecular variability in P. cinctum, which is under-studied and which may uncover geographic or ecological correlations or even the existence of cryptic species.     

The effect of white-rot basidiomycetes on chemical composition andin Vitro digestibility of wheat straw

Five white-rot basidiomycetes were evaluated for their potential to improve ruminal degradation of wheat straw.Polyorus brumalis, Lyophyllum ulmarium III,Trametes gibbosa, Pleurotus ostreatus, and aPleurotus ostreatus mutant were incubated on wheat straw for 30 d at 28°C. Detergent fiber, crude protein andin vitro dry matter digestibility (IVDMD) were determined. The results showed increasing crude protein and ash contents in fungus-treated straw. IVDMD values were increased in straws treated withP. ostreatus, P. ostreatus mutant andT. gibbosa only. Relative to untreated wheat straw the detergent fiber content—neutral detergent fiber (NDF), and acid detergent fiber (ADF) was reduced in fungus-treated straw and out of three fractions—hemicellulose, cellulose and lignin, hemicellulose showed the largest proportionate loss whereas lignin the smallest one in all 5 samples of fungus treated straw.     

Polyclonal immunoglobulin response of thymic,hepatic and splenic lymphocytes from fetal,germ-free and conventionally reared pigs to different B-cell activators

Immunoglobulin (Ig) response to different polyclonal B-cell activators was measured by ELISA in cell culture media of thymocytes, splenocytes and liver cells isolated from pig fetuses, 8-d-old germ-free piglets and conventionally reared pigs. Both in fetal and in postnatal life polyclonally stimulated lymphocytes were found to produce predominantly the IgM isotype; the first IgM formation was detected in 50-d-old fetal liver (gestation in pigs lasts 114 d). Surprisingly, 73-d-old fetal thymic cells were shown to be induced to Ig synthesis and secretion. In contrast to splenocytes of the same age, which secreted exclusively IgM, fetal thymocytes produced IgM, IgG and IgA. Polyclonally stimulated splenic cells as compared with thymic cells started to produce IgA later in fetal ontogeny, whereas the IgG response was not detectable in splenic cell culture media during the whole embryonal development and appeared only after birth. The earliest and the highest Ig stimulation was found after cultivation of lymphocytes withNocardia delipidated cell mitogen. Interestingly, the moderate stimulatory effect of 65-kDa heat shock protein (Hsp-65) in polyclonal IgM response of fetal splenocytes was observed. We showed that thymic B lymphocytes represent probably the first maturing B cell population detectable in fetal life, which is able to differentiate after polyclonal stimulation into IgM as well as IgA and IgG producing cells. Dedicated to Professor J. Šterzl on the occasion of his 70th birthday     

Optimization of fermentation medium by a modified method of genetic algorithms

Summary During the study of mevinolin biosynthesis by Aspergillus terreus ATCC 20542, 10 different medium components were selected for medium optimization. A new optimization method based on genetic algorithms and inductive learning was used for experimental design. For better efficiency the method was supported by a model, constructed with machine learning method, to predict the productivity. In four generations of fermentation experiments the productivity increased nearly three times.     

Behavioural and physiological plasticity of gypsy moth larvae to host plant switching

Larvae of the gypsy moth, Lymantria dispar L. (Lepidoptera: Lymantriidae), a generalist species, frequently encounter spatial and temporal variations in diet quality. Such variation favoured the evolution of high behavioural and physiological plasticity which, depending on forest stand composition, enables more or less successful exploitation of the environment. Even in mixed oak stands, a suitable habitat, interspecific and intraspecific host quality variation may provoke significant variation in gypsy moth performance and, consequently, defoliation severity. To elucidate the insufficiently explored relationship between gypsy moth and oaks (Fagaceae), we carried out reciprocal switches between Turkey oaks (Quercus cerris L.) and less nutritious Hungarian oaks (Quercus frainetto Ten.) (TH and HT groups), under controlled laboratory conditions, and compared larval performance between the switched larvae and larvae continuously fed on either Turkey oak (TT) or Hungarian oak (HH). We found that larval traits were most strongly affected by among‐tree variation in oak quality and identity of the host consumed during the fourth instar. Switching from Turkey to Hungarian oak (TH) led to a longer period of feeding, decrease of mass gain, growth, and consumption rate, lower efficiency of food use and nutrient conversion, and increase of protease and amylase activities. Larvae exposed to the reverse switch (HT) attained values of these traits characteristic for TT larvae. It appeared that the lower growth in the TH group than in the TT group was caused by both behavioural (consumption, pre‐ingestive) and metabolic (post‐digestive) effects from consuming oaks. Multivariate analyses of growth, consumption, and efficiency of food use revealed that early diet experience influenced the sensitivity of the most examined traits to less suitable Hungarian oaks, suggesting the development of behavioural and physiological adjustments. Our results indicate that lower risks of defoliation by gypsy moth might be expected in mixed stands with a higher proportion of Hungarian oak.     

Interaction of extravillous trophoblast galectin-1 and mucin(s)—Is there a functional relevance?

ABSTRACT

In the course of embryo implantation extensive interaction of the trophoblast with uterine tissue is crucial for adequate trophoblast invasion. This interaction is highly controlled, and it has been pointed out that a specific glycocode and changes in glycosylation may be important for successful implantation and maintenance of pregnancy. Both uterine and trophoblast cells have been shown to express cell surface glycoconjugates and sugar binding proteins, such as mucins (MUC) and galectins (gals). An increasing number of studies have investigated potential candidates interacting in this process. However, knowledge about the biochemical nature of the interactions and their importance for trophoblast cell function, and, consequently, for pregnancy outcome are still lacking. This review is aimed at deliberating the possibility that mucins, as heavily glycosylated proteins, might be among the functionally relevant galectin ligands in human trophoblast, based on both published data and our original research.     

Aminoacylation of Bisulphite-modified Yeast Tyrosine Transfer RNA

AS part of a search for the chemical rules underlying the recognition of a tRNA by its aminoacyl-tRNA ligase¹, we are examining the effect of C?U transitions on aminoacylation of tRNA. In this paper, we describe four well-characterized modifications of yeast tRNA^Tyr induced by reaction with bisulphite ions at pH 5.8. Three of the observed changes proved to be C-?U transitions produced by the series of reactions shown in Fig. 1 (refs. 2–5).