Rectangular solid domains in ceramide-cholesterol monolayers - 2D crystals

Very small rectangular domains were observed by atomic force microscopy in binary monolayers of synthetic ceramides and cholesterol. When the cholesterol content is increased the domains are bigger although the rectangular shape is retained. The almost perfect shape of the domains indicates two-dimensional single ceramide crystals. Lipid domains in monolayers of this particular shape and size have to our knowledge not been reported in the literature previously.     

Effects of increasing doses of UV-B radiation on photosynthesis and motility inChlamydomonas reinhardtii

Effects of increasing doses of UV-B radiation on photosynthetic efficiency (PE) and motility inChlamydomonas reinhardtii were investigated. The exposure time ranged from 10 to 120 min at 0.73 W/m² UV-B radiation. A decrease in compensation points (CP) was followed by an increase in PE on extending the UV-B treatment up to 60 min. The subsequent increase in PE was accompanied by increasing CPs. Enhanced doses of UV-B radiation thus have a stimulatory effect on the PE inC. reinhardtii. No inhibitory effects could be detected. No statistically significant differences in motility could be observed due to an extremely high variation of values.     

Long-term infusion of nutrients (total parenteral nutrition) suppresses circulating ghrelin in food-deprived rats

BACKGROUND: Ghrelin derives from endocrine cells (A-like cells) in the stomach (mainly the oxyntic mucosa). Its concentration in the circulation increases during fasting and decreases upon re-feeding. This has fostered the notion that the absence of food in the upper gastrointestinal (GI) tract stimulates the secretion of ghrelin. The purpose of the present study was to determine the concentration of ghrelin in serum and oxyntic mucosa after replacing food with intravenous (iv) infusion of nutrients for 8 days using the technique known as total parenteral nutrition (TPN) MATERIALS AND METHODS: Male Sprague-Dawley rats (200-250 g) were given nutrients (lipids, glucose, amino acids, minerals and vitamins) by iv infusion for 8 days during which time they were deprived of food and water; another group was deprived of food for 24-48 h (fasted controls), while fed controls had free access to food and water. Serum ghrelin, gastrin and pancreastatin concentrations were measured together with the ghrelin content of the oxyntic mucosa. Plasma insulin and glucose as well as serum lipid concentrations were also determined. RESULTS: Fasted rats had higher serum ghrelin than TPN rats and fed controls. The oxyntic mucosal ghrelin concentration (and content) was lower in TPN rats than in fasted rats or fed controls. The serum gastrin and pancreastatin concentrations were lower in TPN rats and fasted rats than in fed controls. The plasma insulin concentration was 87 pmol/l+/-8 (SEM) in TPN rats compared to 101+/-16 pmol/l in fed controls; it was 26+/-14 pmol/l in fasted rats. The basal plasma glucose level was 11+/-0.6 mmol/l in TPN rats and 12+/-0.8 mmol/l in fed controls; it was 7+/-0.3 mmol/l in fasted rats. In TPN rats, the serum concentrations of free fatty acids, triglycerides and cholesterol were increased by 100%, 50% and 25%, respectively, compared to fed controls. Fasted rats had higher circulating concentrations of free fatty acids (20%) and lower concentrations of triglycerides (-40%) than fed controls; fasted rats did not differ from fed controls with respect to serum cholesterol. CONCLUSION: The circulating ghrelin concentration is high in situations of nutritional deficiency (starvation) and low in situations of nutritional plenty (free access to food or TPN). The actual presence or absence of food in the GI tract seems irrelevant. Circulating insulin and glucose concentrations did not differ much between TPN rats and fed controls; serum lipids, however, were elevated in the TPN rats. We suggest that elevated blood lipid levels contribute to the suppression of circulating ghrelin in rats subjected to TPN for 8 days.     

Development and application of a most-probable-number-pcr assay to quantify flagellate populations in soil samples

This paper reports on the first successful molecular detection and quantification of soil protozoa. Quantification of heterotrophic flagellates and naked amoebae in soil has traditionally relied on dilution culturing techniques, followed by most-probable-number (MPN) calculations. Such methods are biased by differences in the culturability of soil protozoa and are unable to quantify specific taxonomic groups, and the results are highly dependent on the choice of media and the skills of the microscopists. Successful detection of protozoa in soil by DNA techniques requires (i) the development and validation of DNA extraction and quantification protocols and (ii) the collection of sufficient sequence data to find specific protozoan 18S ribosomal DNA sequences. This paper describes the development of an MPN-PCR assay for detection of the common soil flagellate Heteromita globosa, using primers targeting a 700-bp sequence of the small-subunit rRNA gene. The method was tested by use of gnotobiotic laboratory microcosms with sterile tar-contaminated soil inoculated with the bacterium Pseudomonas putida OUS82 UCB55 as prey. There was satisfactory overall agreement between H. globosa population estimates obtained by the PCR assay and a conventional MPN assay in the three soils tested.     

Group-Specific PCR Primers to Amplify 24S a-Subunit rRNA Genes from Kinetoplastida (Protozoa) Used in Denaturing Gradient Gel Electrophoresis

We developed and tested a set of primers for amplification of a region of the 24S a-subunit rRNA genes (24S rDNA) specific to Kinetoplastida (Protozoa). The reverse primer was supplied with a GC rich region in the 5? end in order to make the PCR product suitable for analysis by denaturing gradient gel electrophoresis (DGGE). PCR product was obtained from all the kinetoplastids tested and no PCR product was obtained from any other Eukaryotes or Prokaryotes tested. It was possible to distinguish between all pure cultures of kinetoplastids by denaturing gradient gel electrophoresis in gels ranging from 20% to 60% denaturants. PCR-DGGE analysis of DNA purified from lake sediment revealed approximately 20 bands indicating high kinetoplastid diversity. Direct cloning and sequencing of 24S rDNA sequences retrieved from the lake sediment by PCR also showed high kinetoplastid diversity. Of 43 clones, 27 different sequences were found. Alignments and phylogenetic analysis showed that a majority of the sequences were most closely related to the Bodonidae. Four sequences were closer to the Trypanosomatidae, whereas three sequences fell outside both groups. The PCR-DGGE procedure developed in this study has been shown to be useful for distinguishing between different kinetoplastid species. Thus, it may be a useful tool for evaluating the genetic diversity of this group in environmental samples, e.g., as a result of perturbation. Another possible application of this method is in fast and accurate screening for the presence and identification of pathological parasitic Kinetoplastida from environmental samples and for diagnostics of human and animal infections.     

Light-induced linear dichroism in photoreversibly photochromic sensor pigments. – IV. Lack of chromophore rotation in phycochrome b immobilized in vitro

In photochromic pigments, immobilized on Sepharose beads to prevent reorientation of the molecules, linear absorption dichroism can be induced with plane-polarized light. This phenomenon was used to study the relation between the carrier protein and the chromophore in the photochromic cyanobacterial pigment, phycochrome b , from Tolypothrix distorta var. symplocoides Hansgirg, strain UTEX 424 (formerly IUCC 424). It was found that the transition moment of the chromophore has the same direction with respect to the protein in the long-wavelength and the short-wavelength forms of phycochrome b. This contrasts to earlier results for phytochrome in higher plants, in which the transition moment was found to rotate 32° (or 180°—32°) when the long-wavelength form was converted to the short-wavelength form or vice versa.