Survival Rate and Enzyme Activities ofLactobacillus acidophilusFollowing Frozen Storage

The ability of two strains of Lactobacillus acidophilus, CRL 640 and CRL 800, to survive and retain their biological activities under frozen storage was determined. Freezing and thawing, as well as frozen storage, damaged the cell membrane, rendering the microorganisms sensitive to sodium chloride and bile salts. Both lactic acid production and proteolytic activity were depressed after 21 days at -20 degreesC, whereas beta-galactosidase activity per cell unit was increased. Cell injury was partially overcome after repair in a salt-rich medium. Copyright 1998 Academic Press.     

Relationships among msx gene structure and function in zebrafish and other vertebrates

The zebrafish genome contains at least five msx homeobox genes, msxA, msxB, msxC, msxD, and the newly isolated msxE. Although these genes share structural features common to all Msx genes, phylogenetic analyses of protein sequences indicate that the msx genes from zebrafish are not orthologous to the Msx1 and Msx2 genes of mammals, birds, and amphibians. The zebrafish msxB and msxC are more closely related to each other and to the mouse Msx3. Similarly, although the combinatorial expression of the zebrafish msx genes in the embryonic dorsal neuroectoderm, visceral arches, fins, and sensory organs suggests functional similarities with the Msx genes of other vertebrates, differences in the expression patterns preclude precise assignment of orthological relationships. Distinct duplication events may have given rise to the msx genes of modern fish and other vertebrate lineages whereas many aspects of msx gene functions during embryonic development have been preserved.      

The physiological basis of seed dormancy in Avena fatua. II. On the involvement of alternative respiration in the stimulation of germination by sodium azide

Chromatography on DEAE-cellulose of an extract from etiolated leaves of sorghum ( Sorghum vulgare Pers. cv. INRA 450), a C₄ plant, gave only one form of phosphoenol pyruvate carboxylase with functional and regulatory properties of a C₃ type plant enzyme. Greening of the leaves resulted in a significant increase in activity. This increase was due to the appearance of a new form of the enzyme, which eluted at lower ionic strength and exhibited new properties. This form was glucose-6-P activated and showed a sigmoidal curve response to the concentration of the substrate phosphoerralpyruvate. These kinetic properties are typical of a C₄ plant enzyme.     

Drug transfer into target helminth parasites

The pharmacokinetics of an anthelmintic drug includes the time course of drug absorption, distribution, metabolism and elimination from the host and determines the concentration of the active drug that reaches the location of the parasite. However, the action of the anthelmintic also depends on the ability of the active drug to reach its specific receptor within the target parasite. Thus, drug entry and accumulation in target helminths are important issues when considering how best to achieve optimal efficacy. Passive drug transfer through the external helminth surface is the predominant entry mechanism for most widely used anthelmintics and is discussed in this article. Despite the structural differences between the external surface of nematodes (the cuticle) and the external surface of cestodes and trematodes (the tegument), the mechanism of drug entrance into both types of helminth depends on the lipophilicity of the anthelmintic and this is the major physicochemical determinant for the drug to reach a therapeutic concentration in the target parasite. Understanding the processes that regulate drug transfer into helminth parasites is an important aspect in improving the control of parasites in human and veterinary medicine.     

Drug transport mechanisms in helminth parasites: passive diffusion of benzimidazole anthelmintics

Anthelmintic molecules must reach their receptors inside target parasites to exert the pharmacological effect. Available data suggest that the main route of entry of antiparasitic drugs into helminth parasites would be through their external surface. However, it is unclear if trans-tegumental/cuticular penetration is the most important way of entry of benzimidazole (BZD) anthelmintics into their target parasites compared to oral ingestion. The relative involvement of active and passive transport mechanisms has not been defined. The goal of the work reported here was to determine the main processes involved in the entry of BZD anthelmintic molecules into the three main classes of helminth parasites. Adult specimens of Moniezia benedeni (cestode), Fasciola hepatica (trematode) and Ascaris suum (nematode) were incubated in Kreb's Ringer Tris buffer (pH 7.4, 37 degrees C) (1g parasite/10 ml incubation medium) for 15, 45, and 90 min, respectively, in the presence of a concentration gradient of either fenbendazole (FBZ), oxfendazole or triclabendazole sulphoxide (TCBZSO) (1-30 mol/ml, n=4). Dead helminth specimens were also incubated with the same drug concentration gradient. Specimens of F. hepatica with the oral route closed off by ligation were incubated with TCBZSO in the presence or absence of bovine serum albumin. After the incubation time elapsed, samples of parasite material were chemically extracted and prepared for high performance liquid chromatography analysis to measure drug/metabolite concentrations. Equivalent drug concentrations were measured within ligated and non-ligated liver flukes, demonstrating that BZD do mainly penetrate by trans-tegumental diffusion. The higher the concentration of BZD molecules in the incubation medium, the greater their concentration recovered within the helminth parasites. High correlation coefficients (>0.98) were obtained between initial drug concentration in the incubation medium and those measured inside the nematode, cestode, and trematode parasites. FBZ concentrations recovered from tissues of dead cestodes/nematodes over time were significantly greater compared to those measured in living parasites. These differences in drug diffusion may be related to the morphological/functional properties of the parasite's external surfaces. The outcome of the work reported here indicates that passive drug transfer through the external helminth surface is the main transport mechanism accounting for BZD accumulation into target parasites.     

Validité de la somme angulaire comme technique d’extraction d’images planaires à partir de données tomoscintigraphiques pulmonaires de ventilation-perfusion

The aim of our study was to assess the concordance between the results of angular summed images obtained from lung SPECT data versus true planar images in the diagnosis of pulmonary embolism. One hundred and ten patients suspected of pulmonary embolism included in a prospective study underwent a planar lung scan and a lung SPECT. Planar images were extracted from SPECT data using an angular summing technique. Both modalities were reviewed according to revised Pioped criteria by two nuclear medicine physicians. Concordance between modalities and observers was compared with a weighted kappa test. A good degree of agreement between the two modalities (κ = 0.696) were found. Interobserver degree of agreement was similar in planar images (κ = 0.919) and in angular summed images (κ = 0.903). These results suggest that angular sum images from SPECT data are usable and concordant with ventilation perfusion planar images.     

Nucleotide sequence analysis of the lemur beta-globin gene family: evidence for major rate fluctuations in globin polypeptide evolution

Lemur beta-related globin genes have been isolated and sequenced. Orthology of prosimian and human epsilon-, gamma-, and beta-related globin genes was established by dot-matrix analysis. All of these lemur globin genes potentially encode functional beta-related globin polypeptides, though precisely when the gamma-globin gene is expressed remains unknown. The organization of the 18-kb brown lemur beta-globin gene cluster (5' epsilon-gamma-[psi eta-delta]-beta 3') is consistent with its evolution by contraction via unequal crossing-over from the putative ancestral mammalian beta-globin gene cluster (5' epsilon-gamma- eta-delta-beta 3'). The dwarf lemur nonadult globin genes are arranged as in the brown lemur. Similar levels of synonymous (silent) nucleotide substitutions and noncoding DNA sequence differences have accumulated between species in all of these genes, suggesting a uniform rate of noncoding DNA divergence throughout primate beta-globin gene clusters. These differences are comparable with those observed in the nonfunctional psi eta pseudogene and have therefore accumulated at the presumably maximal neutral rate. In contrast, nonsynonymous (replacement) nucleotide substitutions show a significant heterogeneity in distribution for both the same gene in different lineages and different genes in the same lineage. These major fluctuations in replacement but not silent substitution rates cannot be attributed to changes in mutation rate, suggesting that changes in the rate of globin polypeptide evolution in primates is not governed solely by variable mutation rates.      

The small-subunit ribosomal RNA gene sequences from the hypotrichous ciliates Oxytricha nova and Stylonychia pustulata

We have determined the complete nucleotide sequence of the small- subunit ribosomal RNA genes for the ciliate protozoans Stylonychia pustulata and Oxytricha nova. The sequences are homologous and sufficiently similar that these organisms must be closely related. In a phylogeny inferred from comparisons of several eukaryotic small-subunit ribosomal RNAs, the divergence of the ciliates from the eukaryotic line of descent is seen to coincide with the radiation of the plants, the animals, and the fungi. This radiation is preceded by the divergence of the slime mold, Dictyostelium discoideum.