An improved model for determining degree-day values from daily temperature data

Although using hourly weather data offers the greatest accuracy for estimating growing degree-day values, daily maximum and minimum temperature data are often used to estimate these values by approximating the diurnal temperature trends. This paper presents a new empirical model for estimating the hourly mean temperature. The model describes the diurnal variation using a sine function from the minimum temperature at sunrise until the maximum temperature is reached, another sine function from the maximum temperature until sunset, and a square-root function from then until sunrise the next morning. The model was developed and calibrated using several years of hourly data obtained from five automated weather stations located in California and representing a wide range of climate conditions. The model was tested against an additional data-set at each location. The temperature model gave good results, the root-mean-square error being less than 2.0 °C for most years and locations. The comparison with published models from the literature showed that the model was superior to the other methods. Hourly temperatures from the model were used to calculate degree-day values. A comparison between degree-day estimates determined from the model and those obtained other selected methods is presented. The results showed that the model had the best accuracy in general regardless of the season. Received: 25 October 2000 / Revised: 2 July 2001 / Accepted: 2 July 2001     

Lack of coupling of D-2 receptors to adenylate cyclase in GH-3 cells exposed to epidermal growth factor. Possible role of a differential expression of Gi protein subtypes.

Exposure of GH-3 cells to epidermal growth factor for 4 consecutive days induced the expression of both D-2(415) and D-2(444) dopamine-receptor isoforms. Epidermal growth factor also promoted a remarkable increase in the content of Gi3 protein, which is responsible for receptor-induced activation of potassium channels in GH-3 cells. D-2 receptors in this model apparently activate a specific transducing pathway, leading to opening of potassium channels and inhibition of prolactin release by cAMP-independent mechanisms. This is shown by: 1) the selective D-2 agonist quinpirole, while inactive on vasoactive intestinal peptide-induced prolactin release, strongly inhibited the hormone secretion induced by neurotensin; 2) quinpirole, up to 100 microM, did not inhibit cAMP production evoked by vasoactive intestinal peptide both in intact cells and in broken cell membrane preparations; and 3) quinpirole and other D-2 agonists strongly potentiated Rb+ efflux when measured in a nominally calcium-free reaction solution containing 100 mM potassium (voltage-dependent component), but did not modify Rb+ efflux if measured in a reaction solution containing 1 mM calcium and 5 mM potassium (calcium-activated, cAMP-dependent component).     

The Thrombospondin-related Protein Family of Apicomplexan Parasites: The Gears of the Cell Invasion Machinery

A number of severe diseases of medical and veterinary importance are caused by parasites of the phylum Apicomplexa. These parasites invade host cells using similar subcellular structures, organelles and molecular species. Proteins containing one or more copies of the type I repeat of human platelet thrombospondin (TSP1), are crucial components of both locomotion and invasion machinery. Members of this family have been identified in Eimeria tenella, E. maxima, Toxoplasma gondii, Cryptosporidium parvum and in all Plasmodium species so far analysed. Here, Andrea Crisanti and colleagues discuss the structure, localization and current understanding of the function of TSP family members in the invasion of target cells by apicomplexan parasites.     

Changes of the hepatic proteome in hepatitis B-infected mouse model at early stages of fibrosis

Liver fibrosis (LF) is the accumulation of extracellular matrix (ECM) proteins due to chronic liver injury. We used two-dimensional differential in-gel electrophoresis (2D-DIGE) to perform a comparative analysis of cytosolic and nuclear protein patterns of nontransgenic (NTg) and HBV transgenic (Tg) mice livers at early stages of fibrosis. We identified several candidate proteins, involved in a variety of pathways, which could be used as putative biomarkers for LF early detection.     

Purification,primary structure,and properties of <Emphasis Type="Italic">Euphorbia characias</Emphasis> latex purple acid phosphatase

A purple acid phosphatase was purified to homogeneity from Euphorbia characias latex. The native protein has a molecular mass of 130 ± 10 kDa and is formed by two apparently identical subunits, each containing one Fe(III) and one Zn(II) ion. The two subunits are connected by a disulfide bridge. The enzyme has an absorbance maximum at 540 nm, conferring a characteristic purple color due to a charge-transfer transition caused by a tyrosine residue (Tyr172) coordinated to the ferric ion. The cDNA nucleotide sequence contains an open reading frame of 1392 bp, and the deduced sequence of 463 amino acids shares a very high degree of identity (92–99%) to other purple acid phosphatases isolated from several higher plants. The enzyme hydrolyzes well p-nitrophenyl phosphate, a typical artificial substrate, and a broad range of natural phosphorylated substrates, such as ATP, ADP, glucose-6-phosphate, and phosphoenolpyruvate. The enzyme displays a pH optimum of 5.75 and is inhibited by molybdate, vanadate, and Zn²⁺, which are typical acid phosphatase inhibitors.     

Solution structure of an alternate conformation of helix27 from Escherichia coli16S rRNA

Helix (H)27 of 16S ribosomal (r)RNA from Escherichia coli was dubbed the "switch helix" when mutagenesis suggested that two alternative base pair registers may have distinct functional roles in the bacterial ribosome. Although more recent genetic analyses suggest that H27 conformational switching is not required for translation, previous solution studies demonstrated that the isolated E. coli H27 can dynamically convert between the 885 and 888 conformations. Here, we have solved the nuclear magnetic resonance solution structure of a locked 888 conformation. NOE and residual dipolar coupling restraints reveal an architecture that markedly differs from that of the 885 conformation found in crystal structures of the bacterial ribosome. In place of the loop E motif that characterizes the 885 conformer and that the 888 conformer cannot adopt, we find evidence for an asymmetrical A-rich internal loop stabilized by stacking interactions among the unpaired A's. Comparison of the isolated H27 888 solution structure with the 885 crystal structure within the context of the ribosome suggests a difference in overall length of H27 that presents one plausible reason for the absence of H27 conformational switching within the sterically confining ribosome.     

Efficiency of PCR-based methods in discriminating Bifidobacterium longum ssp. longum and Bifidobacterium longum ssp. infantis strains of human origin

Bifidobacterium longum is considered to play an important role in health maintenance of the human gastrointestinal tract. Probiotic properties of bifidobacterial isolates are strictly strain-dependent and reliable methods for the identification and discrimination of this species at both subspecies and strain levels are thus required. Differentiation between B. longum ssp. longum and B. longum ssp. infantis is difficult due to high genomic similarities. In this study, four molecular-biological methods (species- and subspecies-specific PCRs, random amplified polymorphic DNA (RAPD) method using 5 primers, repetitive sequence-based (rep)-PCR with BOXA1R and (GTG)₅ primers and amplified ribosomal DNA restriction analysis (ARDRA)) and biochemical analysis, were compared for the classification of 30 B. longum strains (28 isolates and 2 collection strains) on subspecies level. Strains originally isolated from the faeces of breast-fed healthy infants (25) and healthy adults (3) showed a high degree of genetic homogeneity by PCR with subspecies-specific primers and rep-PCR. When analysed by RAPD, the strains formed many separate clusters without any potential for subspecies discrimination. These methods together with arabionose/melezitose fermentation analysis clearly differentiated only the collection strains into B. longum ssp. longum and B. longum ssp. infantis at the subspecies level. On the other hand, ARDRA analysis differentiated the strains into the B. longum/infantis subspecies using the cleavage analysis of genus-specific amplicon with just one enzyme, Sau3AI. According to our results the majority of the strains belong to the B. longum ssp. infantis (75%). Therefore we suggest ARDRA using Sau3AI restriction enzyme as the first method of choice for distinguishing between B. longum ssp. longum and B. longum ssp. infantis.     

Expression of Lactobacillus brevis IOEB 9809 tyrosine decarboxylase and agmatine deiminase genes in wine correlates with substrate availability

Aims: Lactobacillus brevis IOEB 9809 is able to produce both tyramine and putrescine via tyrosine decarboxylase and agmatine deiminase enzymes, respectively, when cultured on synthetic media. The aims of this study were to assess the expression of L. brevis IOEB 9809 tdc and aguA1 genes, during wine fermentation and to evaluate the effect of substrate availability and pH on tdc and aguA1 expression, as well as on biogenic amine production and L. brevis viability. Methods and Results: The relative expression of L. brevis IOEB 9809 tdc and aguA1 genes was analysed in wine by quantitative real‐time RT‐PCR (qRT‐PCR) during a period of incubation of 30 days. Cell viability, pH values, putrescine and tyramine concentration were monitored throughout the experiments. Conclusions: The wine trials indicated that L. brevis IOEB 9809 is able to produce both tyramine and putrescine during wine fermentation. Increased cell viability was also observed in wine supplemented with tyrosine or agmatine. qRT‐PCR analysis suggests a strong influence of substrate availability on the expression of genes coding for tyrosine decarboxylase and agmatine deiminase in L. brevis IOEB 9809. Less evident is the relationship between putrescine and tyramine production and tolerance to wine pH. Significance and Impact of Study: To our knowledge, this study represents the first assessment of relative expression of L. brevis IOEB 9809 genes involved in biogenic amine production in wine. Furthermore, an effect of biogenic amine production on viability of L. brevis during wine fermentation was established.     

Probiotic abilities of riboflavin-overproducing Lactobacillus strains: a novel promising application of probiotics

The probiotic potential of Lactobacillus plantarum and Lactobacillus fermentum strains, capable of overproducing riboflavin, was investigated. The riboflavin production was quantified in co-cultures of lactobacilli and human intestinal epithelial cells, and the riboflavin overproduction ability was confirmed. When milk and yogurt were used as carrier matrices, L. plantarum and L. fermentum strains displayed a significant ability to survive through simulated gastrointestinal transit. Adhesion was studied on both biotic and abiotic surfaces. Both strains adhered strongly on Caco-2 cells, negatively influenced the adhesion of Escherichia coli O157:H7, and strongly inhibited the growth of three reference pathogenic microbial strains. Resistance to major antibiotics and potential hemolytic activity were assayed. Overall, this study reveals that these Lactobacillus stains are endowed with promising probiotic properties and thus are candidates for the development of novel functional food which would be both enriched in riboflavin and induce additional health benefits, including a potential in situ riboflavin production, once the microorganisms colonize the host intestine.