Gas exchange characteristics of<Emphasis Type="Italic"> Pinus canariensis</Emphasis> needles in a forest stand on Tenerife,Canary Islands

Gas exchange characteristics and chlorophyll fluorescence of the Canarian endemic pine ( Pinus canariensis) were measured during the day for a year in a field stand on Tenerife, Canary Islands, Spain. Diurnal tendencies of gas exchange were variable depending on ambient conditions. In general they paralleled photosynthetic photon flux density with only one peak at midday, except on summer days with high air vapour pressure deficit (VPD), when needles exhibited a severe midday depression of CO ₂ assimilation rate ( A), in parallel with a reduction of stomatal conductance ( g _s). The internal CO ₂ concentration tendencies during the day suggest that stomatal closure was the main cause of the midday depression of photosynthesis. Chlorophyll fluorescence data corroborate this assertion, with the parameter F _v/ F _m reaching high values throughout day and year. P. canariensis living in the sub-tropic exhibited high values of A (maximal A value of 17 µmol m ^-2 s ^-1) and high optimal needle temperature for photosynthesis (25°C) which were at the upper limit of the values given for conifers and similar only to data obtained for some pine species adapted to habitats at similar latitudes. g _s was reduced to half when VPD attained 40 mbar, allowing this pine to have high A/ g _s values during high evaporative demand conditions.     

Subpopulation characteristics of egg-contaminating Salmonella enterica serovar Enteritidis as defined by the lipopolysaccharide O chain

Characterization of Salmonella enterica serovar Enteritidis was refined by incorporating new data from isolates obtained from avian sources, from the spleens of naturally infected mice, and from the United Kingdom into an existing lipopolysaccharide (LPS) O-chain compositional database. From least to greatest, the probability of avian isolates producing high-molecular-mass LPS O chain ranked as follows: pooled kidney, liver, and spleen; intestine; cecum; ovary and oviduct; albumen; yolk; and whole egg. Mouse isolates were most like avian intestinal samples, whereas United Kingdom isolates were most like those from the avian reproductive tract and egg. Non-reproductive tract organ isolates had significant loss of O chain. Isogenic isolates that varied in ability to make biofilm and to be orally invasive produced different O-chain structures at 25 degrees C but not at 37 degrees C. Hens infected at a 91:9 biofilm-positive/-negative colony phenotype ratio yielded only the negative phenotype from eggs. These results indicate that the environment within the hen applies stringent selection pressure on subpopulations of S. enterica serovar Enteritidis at certain points in the infection pathway that ends in egg contamination. The avian cecum, rather than the intestines, is the early interface between the environment and the host that supports emergence of subpopulation diversity. These results suggest that diet and other factors that alter cecal physiology should be investigated as a means to reduce egg contamination.     

Measuring antioxidants in tree species in the natural environment: from sampling to data evaluation

Biochemical measurements of antioxidants and protective pigments have been successfully introduced as markers of environmental stress in field studies (mainly forest studies). A guideline for field sampling and analysis methods is required to allow better comparison of data from different studies. The present review paper recommends HPLC methods for the analysis of ascorbate and glutathione (in oxidized and reduced form), tocopherols, and chloroplast pigments. Methodological variations are substantially lower (coefficients of variance of repeated extractions typically 4-9%) than biological variations of field samples (typical variation coefficients 8-36%), hence special emphasis is put on considerations of sampling standardization in the field with respect to sample time (seasonal and diurnal) and representative sampling of individuals and tissues. Following the suggestions in this paper would enable researchers to produce results that could be compared with those of several forest studies on conifers published in recent years. A larger data-set available for multivariate statistical evaluations (e.g. principal component analysis and cluster analysis) will enhance the diagnostic value of such investigations.     

Properties of triple helices formed by oligonucleotides containing 8-aminopurines

The synthesis of parallel hairpins carrying 8-aminopurines is described. These hairpins have a high affinity for specific polypyrimidine sequences resulting in the formation of very stable triplexes.     

Swimming of pregnant rats at different water temperatures

We studied the chronic effect of exercise during water immersion, associated with thermal stress (water temperature at 22, 35 and 40 degrees C) at an intensity of 80% of maximal work load supported in pregnant rats (P) and non-pregnant female rats (NP). P and NP were subdivided into three subgroups according to water temperature during exercise (P22 and NP22; P35 and NP35; P40 and NP40). The animals were submitted to daily swimming sessions of 10-15 min, for 19 days of pregnancy (P) or experimental conditions (NP). Plasma concentration of triglycerides, cholesterol, glucose, total protein, albumin and corticosterone were determined 24 h after the last exercise session. Weight gain and rectal temperature pre- and post-swimming session were also determined. The offspring were examined just after caesarian section on the 20th day of pregnancy to check weight, length and litter size. Pregnant rats showed an increase of triglycerides, reduction of glycemia, total protein and albumin and cholesterol (at 35 degrees C) when compared to non-pregnant animals. Such effects probably lead to an adequate delivery of substrate to the fetus and prepare the mother for lactation. Daily thermal stress did not modify metabolic responses to exercise in pregnant rats. Results also show a deleterious effect on offspring when the mother is exposed daily to extreme temperatures during swimming. These results suggest that water temperature (cold and hot) in swimming have to be considered to avoid damage in fetal development.     

Detection and counting of Cryptosporidium parvum in HCT-8 cells by flowcytometry

The objective of the present study was to evaluate flowcytometry analysis (FCA) as a tool for rapidly and objectively estimating the percentage of cells infected with Cryptosporidium parvum in an in vitro model. We compared the results to those obtained with immunofluorescence assay (IFA) and evaluated the intra-assay variability of both assays and the inter-assay variability of IFA. Human ileocecal adenocarcinoma cells (HCT-8) were infected with different doses of excysted oocysts. After 24 hours, cells were analysed by FCA and by IFA using a monoclonal antibody that recognises a C. parvum antigenic protein and a lectin that binds with glycoproteins present in the parasitophorous vacuoles. The coefficient of variability in terms of the percentage of infected cells was lower for FCA (i.e., 13-14%) than for IFA (i.e., 27-38% when performed by a single operator and 19-22% when performed by three operators), suggesting that FCA is more accurate, in that it is not subject to operator expertise. FCA also has the advantage of allowing the entire culture to be examined, thus avoiding problems with heterogeneity among microscopic fields. In light of these results, this method could also be used to test new anti-Cryptosporidium drugs.     

DNA profile in legal practice

This article shows the main advantages and drawbacks of the genetic analysis used by magistrates and police officers. Analyze a cellular trace on the scene of a crime, seek a paternity are some applications.     

Bioelectrical parameters of the whole human body obtained through bioelectrical impedance analysis

Knowledge of electrical properties of body tissues across the frequency spectrum is useful for tissue characterization. The bioelectric impedance analysis method, operating from 1 to 250 kHz (multi-frequency), was used in 23 normal male human subjects between the ages of 21 and 52 years, for estimation of their bioelectrical parameters. Amplitude of the output current was set to 800 microA(RMS). The experimental data showed that bioelectric parameters were highly dependent on frequency and the presence of a threshold frequency around 4 kHz. In order to explain the unusual features observed in our experimental data, the human body was simulated through the Cole-Fricke-Cole model (RC circuit) and the Extended Cole-Fricke-Cole model (RLC circuit). The simulated data showed that the Extended Cole-Fricke-Cole model had a higher accuracy than the traditional Cole-Fricke-Cole model. These results suggest that the unusual features could be due to the possible existence of inductive effects in biological cells and body tissues and that the inductive parameter and the threshold frequency could be used for characterizing the healthy tissues as well as the traditional bioelectric parameters.     

The effects of cold-pretreatment,auxins and carbon source on anther culture of rice

The effects of a cold pretreatment, the concentration of different auxins (2,4-D, NAA and IAA) and the type of carbon source (maltose and sucrose) on the induction of callus from anthers of three parental lines and four rice F₁ hybrids (Japonica × Indica, Indica × Japonica) were studied. The results indicated that a cold pretreatment was essential for the induction of callus from anthers of the parental lines and the F₁ hybrids. These effects were genotype dependent. Auxins were essential for the induction of callus, and the type and concentration of auxins also influenced this process, as well as the type of carbon source. The greatest induction of callus was by the hybrid Morelos A92 × Koshihikari after a cold pretreatment of 8 days using 10.74 M –napthaleneacetic acid and 30 g l^–1 maltose.