Adaptive learning of host preference in a herbivorous arthropod

Although many publications deal with the effects of experience on behaviour, adaptive learning (i.e. behavioural change with experience resulting in improved reproductive success) is poorly documented. We present direct evidence that learning of host preference improves fitness in the herbivorous mite, Tetranychus urticae . Individual mites from two strains were repeatedly given a choice between two host plants, tomato and cucumber, and then subjected to a performance test on each. For both strains, food experience affected the subsequent choice: individual mites learned to prefer cucumber over tomato. The performance test showed this effect to be adaptive, as the food plant the mites learned to prefer (cucumber) allowed for increased oviposition, survival and development. These findings have important implications for the interpretation of the preference–performance relationship among herbivorous arthropods. The frequently reported absence of such a relationship may be due to experience-dependent preference and/or performance.     

Influence of Matricial Molecules on Growth and Differentiation of Entrapped Chondrocytes

Primary cultures of rabbit articular chondrocytes have been cultivated normally and within three-dimensional systems using different alginate matrices. The in vitro proliferation capacity of the cells immobilized in the calcium alginate beads was investigated. The growth curve showed that chondrocytes are able to grow and to divide for several days inside the beads; in parallel an increase in protein contents was also measured. The differentiated phenotype of rabbit articular chondrocytes consists of cartilage-specific proteoglycans. During serial monolayer cultures this phenotype was lost and replaced by a low level of proteoglycan synthesis. On the contrary when cultivated in beads, entrapped cells maintained their differentiated pheno-type over time; the rates of proteoglycan were similar to those of primary chondrocytes. All these parameters were tested comparatively using different substrata in monolayer cultures and in alginate gels. Assays were carried out to assess the influence of type I collagen, type IV collagen, and of fibronectine on the growth as well as on the differentiation phenotype. The encapsulation methodology is readily applicable to the culture of chondrocytes in single beads, in multiwell dishes, or to mass culture for a bioproduction of extracellular matrix components.     

Longterm quiescent cells in the aged human subventricular neurogenic system specifically express GFAP‐δ

A main neurogenic niche in the adult human brain is the subventricular zone (SVZ). Recent data suggest that the progenitors that are born in the human SVZ migrate via the rostral migratory stream (RMS) towards the olfactory bulb (OB), similar to what has been observed in other mammals. A subpopulation of astrocytes in the SVZ specifically expresses an assembly‐compromised isoform of the intermediate filament protein glial fibrillary acidic protein (GFAP‐δ). To further define the phenotype of these GFAP‐δ expressing cells and to determine whether these cells are present throughout the human subventricular neurogenic system, we analysed SVZ, RMS and OB sections of 14 aged brain donors (ages 74‐93). GFAP‐δ was expressed in the SVZ along the ventricle, in the RMS and in the OB. The GFAP‐δ cells in the SVZ co‐expressed the neural stem cell (NSC) marker nestin and the cell proliferation markers proliferating cell nuclear antigen (PCNA) and Mcm2. Furthermore, BrdU retention was found in GFAP‐δ positive cells in the SVZ. In the RMS, GFAP‐δ was expressed in the glial net surrounding the neuroblasts. In the OB, GFAP‐δ positive cells co‐expressed PCNA. We also showed that GFAP‐δ cells are present in neurosphere cultures that were derived from SVZ precursors, isolated postmortem from four brain donors (ages 63‐91). Taken together, our findings show that GFAP‐δ is expressed in an astrocytic subpopulation in the SVZ, the RMS and the OB. Importantly, we provide the first evidence that GFAP‐δ is specifically expressed in longterm quiescent cells in the human SVZ, which are reminiscent of NSCs.     

Evolutionary history of the closely related group 2 coronaviruses: porcine hemagglutinating encephalomyelitis virus, bovine coronavirus, and human coronavirus OC43

The close genetic and antigenic relatedness among the group 2 coronaviruses human coronavirus OC43 (HCoV-OC43), bovine coronavirus (BCoV), and porcine hemagglutinating encephalomyelitis virus (PHEV) suggests that these three viruses with different host specificities diverged fairly recently. In this study, we determined the complete genomic sequence of PHEV (strain PHEV-VW572), revealing the presence of a truncated group 2-specific ns2 gene in PHEV in comparison to other group 2 coronaviruses. Using a relaxed molecular clock approach, we reconstructed the evolutionary relationships between PHEV, BCoV, and HCoV-OC43 in real-time units, which indicated relatively recent common ancestors for these species-specific coronaviruses.     

In Vitro Protein Synthesis by Plastids of Phaseolus vulgaris: IV. Amino Acid Incorporation by Etioplasts and Effect of Illumination of Leaves on Incorporation by Plastids 1

Protein synthesis in vitro by etioplasts and chloroplasts from Phaseolus vulgaris was examined to study the factors regulating the development of etioplasts into chloroplasts. The properties of incorporation of (14)C-leucine into protein by etioplasts from plants grown 6.5 days in darkness are similar to those of chloroplasts from plants of the same age that were illuminated for 12 hours. However, the rate of incorporation per plastid by chloroplasts is 4 times higher than the rate of amino acid incorporation by etioplasts. When 6-day-old plants are placed in light, this 4-fold increase occurs within 6 hours and is maintained up to 36 hours. The difference in rate of amino acid incorporation into protein between etioplasts and chloroplasts represents a real difference in the ability of etioplasts and chloroplasts to synthesize protein. A difference in pool size of leucine between etioplasts and chloroplasts does not account for the difference in amino acid incorporation between etioplasts and chloroplasts. Also the difference in photosynthetic capabilities of etioplasts and chloroplasts does not account for the difference in the ability to incorporate amino acid into protein. Furthermore, there are no factors in homogenates of etiolated leaves which inactivate amino acid incorporation into protein by chloroplasts. The difference in rates of amino acid incorporation between etioplasts and chloroplasts is correlated with the state of development of the plastids. The plastids have increased ability to incorporate amino acid into protein when the plastids are undergoing growth and differentiation.     

Ageing,opioid analgesia and the pineal gland

The effects of ageing on day-night rhythms of analgesia was examined with young (1–2 months), mature (8–12 months) and old (20–30 months) mice. Significant age-related declines were observed both in the absolute levels and diel rhythms of morphine analgesia, with the most pronounced changes occuring at night. Administration of the pineal hormone, melatonin, augmented day-time levels of analgesia in all age classes and reversed the age-related decline in nocturnal morphine analgesia in old mice. Inhibition of pineal function in young mice by either exposure to light pulses or treatment with benserazide mimicked the effects of ageing on nocturnal morphine analgesia. These findings suggest that the pineal gland and melatonin are involved in modulating diel rhythms of analgesia and have an influential role on age-related changes in opioid responses.     

Metabolic engineering of a xylose-isomerase-expressing Saccharomyces cerevisiae strain for rapid anaerobic xylose fermentation

After an extensive selection procedure, Saccharomyces cerevisiae strains that express the xylose isomerase gene from the fungus Piromyces sp. E2 can grow anaerobically on xylose with a mu(max) of 0.03 h(-1). In order to investigate whether reactions downstream of the isomerase control the rate of xylose consumption, we overexpressed structural genes for all enzymes involved in the conversion of xylulose to glycolytic intermediates, in a xylose-isomerase-expressing S. cerevisiae strain. The overexpressed enzymes were xylulokinase (EC 2.7.1.17), ribulose 5-phosphate isomerase (EC 5.3.1.6), ribulose 5-phosphate epimerase (EC 5.3.1.1), transketolase (EC 2.2.1.1) and transaldolase (EC 2.2.1.2). In addition, the GRE3 gene encoding aldose reductase was deleted to further minimise xylitol production. Surprisingly the resulting strain grew anaerobically on xylose in synthetic media with a mu(max) as high as 0.09 h(-1) without any non-defined mutagenesis or selection. During growth on xylose, xylulose formation was absent and xylitol production was negligible. The specific xylose consumption rate in anaerobic xylose cultures was 1.1 g xylose (g biomass)(-1) h(-1). Mixtures of glucose and xylose were sequentially but completely consumed by anaerobic batch cultures, with glucose as the preferred substrate.     

Experimental comparative studies of the reactibility of lung tissue to intratracheally introduced ash produced by power plants

There was analysed the behaviour of the pulmonary tissue in white Wistar female rats exposed to a single effect of electroenergetic ashes from a few Polish power stations, hasting plants and electrohasting plants. The animals received a single 0.6 ml dose of the ashes in suspension of physiologic fluid intratracheally; 3 and 6 months after the experiment, the animals were decapitated and material for examinations was collected. Grains of used ashes were then assessed under the scanning electron microscope. Segments were stained with hematoxyline and cosine and by Masson's method. All the ashes caused inflammatory infiltrations, granulomas containing grains of the examined ash, fibrosis, thickening of interalveolar septa, atelectasis, and emphysema. The experiment resulted in a disturbance of biological balance of pulmonary connective tissue (stroma) due to the action of the ashes.     

Preface

Biological Trace Element Research -