Virulence of South African isolates of Haemophilus paragallinarum. Part 3: experimentally produced NAD-independent isolate

A NAD-dependent isolate 46 (C-3) of Haemophilus paragallinarum, which was previously demonstrated to be of high virulence, was transformed to NAD independence using a plasmid isolated from a naturally occurring NAD-independent isolate of H. paragallinarum. The transformation was performed by two different methods and the identity of all of the isolates, before and after transformation was confirmed using a H. paragallinarum-specific PCR test. The transformed NAD-independent serovar C-3 isolate and the wild-type serovar C-3 isolate were used to experimentally infect vaccinated layer chickens. It was shown that the transformation to NAD independence significantly altered the virulence of the serovar C-3 isolate that was used in the transformation experiment. The mechanisms responsible for a decrease in virulence are not clear, but may be related to the pathology of the transformed isolate in the sinus of the chickens.     

The Distribution of Bovine Trypanosomosis in Zimbabwe and an Evaluation of the Value of an Anti-trypanosomal Antibody Detection ELISA as a Tool for Monitoring the Effectiveness of Tsetse Control Operations

Tsetse have been cleared from large areas of Zimbabwe during the past 65 years. In most areas, they are prevented from re-invading cleared areas by barriers of odour-baited, insecticide-treated targets. A trypanosomosis survey was conducted to determine the effectiveness of such barriers against re-invasion and to confirm the absence of tsetse in areas where they had previously been eradicated. Parasitological diagnostic methods and an anti-trypanosomal antibody detection enzyme-linked immunosorbent assay (antibody ELISA) were used. The prevalence of trypanosomal infections in the tsetse-cleared areas was generally low. However, the prevalence of anti-trypanosomal antibodies was unexpectedly high in some areas. This high proportion of cattle with antibodies could, in most cases, be explained by recent or historic information on the distribution and density of tsetse. The results from the survey demonstrated the value of anti-trypanosomal antibody detection as an additional sensitive tool for monitoring the effectiveness of tsetse control operations.     

Does resource complementarity or prevention of lodging contribute to the increased productivity of rice varietal mixtures in Yunnan,China?

We conducted an experiment in Gejiu, Yunnan Province of China during the wet season of 2002 to examine the importance of resource complementarity and prevention of lodging in the fast-spreading practice of growing rice varietal mixtures in China to suppress rice blast disease and its associated damage. The hybrid rice variety Shanyou 63 and the glutinous or sticky rice variety Huangkenuo were used to study intra- and inter-varietal competition in the rice intercropping system. The experiment was laid out as a randomized complete block design in four replications with pure stands and mixtures of both varieties at different total planting densities and mixing ratios. In half of the pure stand treatments of glutinous rice a metal frame was installed to prevent lodging. The results showed that resource complementarity between the two rice varieties, resulting from niche differentiation, was marginal and did not greatly enhance the productivity of the rice varietal mixtures. In contrast, prevention of lodging of glutinous rice was identified as an important additional advantage of growing these rice varieties in mixture.     

Fucose-Rich Sulfated Polysaccharides from Two Vietnamese Sea Cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera: Structures and Anticoagulant Activity

Fucosylated chondroitin sulfates (FCSs) FCS-BA and FCS-HS, as well as fucan sulfates (FSs) FS-BA-AT and FS-HS-AT were isolated from the sea cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera, respectively. Purification of the polysaccharides was carried out by anion-exchange chromatography on DEAE-Sephacel column. Structural characterization of polysaccharides was performed in terms of monosaccharide and sulfate content, as well as using a series of non-destructive NMR spectroscopic methods. Both FCSs were shown to contain a chondroitin core [→3)-β-d-GalNAc-(1→4)-β-d-GlcA-(1→]_n bearing sulfated fucosyl branches at O-3 of every GlcA residue in the chain. These fucosyl residues were different in pattern of sulfation: FCS-BA contained Fuc2S4S, Fuc3S4S and Fuc4S at a ratio of 1:8:2, while FCS-HS contained these residues at a ratio of 2:2:1. Polysaccharides differed also in content of GalNAc4S6S and GalNAc4S units, the ratios being 14:1 for FCS-BA and 4:1 for FCS-HS. Both FCSs demonstrated significant anticoagulant activity in clotting time assay and potentiated inhibition of thrombin, but not of factor Xa. FS-BA-AT was shown to be a regular linear polymer of 4-linked α-L-fucopyranose 3-sulfate, the structure being confirmed by NMR spectra of desulfated polysaccharide. In spite of considerable sulfate content, FS-BA-AT was practically devoid of anticoagulant activity. FS-HS-AT cannot be purified completely from contamination of some FCS. Its structure was tentatively represented as a mixture of chains identical with FS-BA-AT and other chains built up of randomly sulfated alternating 4- and 3-linked α-L-fucopyranose residues.     

The role of the National Potato Programme in Colombia

Summary During the past two decades total potato production in Colombia tripled and the annual consumption per capita doubled; the National Potato Programme has probably contributed greatly to these increases. The main activities of this Programme have been in breeding and in successful introduction of new cultivars. This could be achieved because (1) breeding is oriented to the requirements of the growers, (2) breeding is done at high altitude where 85% of the area cropped with potato is located and virus infection pressure is low, (3) the introduction of new cultivars is well organized and (4) with the new cultivars clear instructions on pest and disease control and on growing techniques are given.     

Effects of temperature on growth and photosynthesis in the seedling stage of the sheath blight-resistant rice genotype 32R

The 32R rice genotype is resistant to sheath blight disease (ShB), with a high-yield potential. We examined effects of temperature on the plant responses of 32R in comparison with those of the ShB-susceptible rice genotype (29S) and Nipponbare (Nb, a Japonica standard cultivar). The seedlings at the 4th leaf stage of rice genotypes were exposed to 14/14, 19/14, 25/20, 31/26, 37/32 and 37/37 °C (day/night) for 5, 10 and 15 days. The dry weight, leaf area, photosynthesis, contents of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and chlorophyll contents were examined. The dry weight showed lower in 32R than in 29S and Nb at a low temperature, and total dry weight correlated strongly with root dry weight and leaf area. The relative growth rate (RGR) correlated strongly with the net assimilation rate (NAR). Rubisco, chlorophyll contents and the photosynthetic rates were limited at a low temperature and showed lower in 32R than in 29S and Nb. The strong correlations between Rubisco and the rates of maximum photosynthesis and initial slope were found in 32R, but not found in 29S and Nb. In addition, RGR and NAR of 32R correlated positively with Rubisco. These suggest that 32R contains traits of cold-sensitive genotypes that are related to limiting Rubisco at a low temperature, thus diminishing photosynthesis and limiting plant growth. Differences of growth among 32R, 29S and Nb were discussed in the relation of genotypes.     

Differentiation of Umbilical Cord Lining Membrane-Derived Mesenchymal Stem Cells into Endothelial-Like Cells

Background: Stem cell therapy for the treatment of vascular-related diseases through functional revascularization is one of the most important research areas in tissue engineering. The aim of this study was to investigate the in vitro differentiation of umbilical CL-MSC into endothelial lineage cells. Methods: In this study, isolated cells were characterized for expression of MSC-specific markers and osteogenic and adipogenic differentiation. They were induced to differentiate into endothelial-like cells and then examined for expression of the endothelial-specific markers, karyotype, and functional behavior of cells. Results: Isolated cells expressed MSC-specific markers and differentiated into adipocytes and osteoblasts. After endothelial differentiation, they expressed CD31, vWF, VE-cadherin, VEGFR1, and VEGFR2 at both mRNA and protein level, but their morphological changes were not apparent when compared with those of undifferentiated cells. There were no significant changes in karyotype of differentiated cells. Furthermore, angiogenesis assay and LDL uptake assay showed that differentiated cells were able to form the capillary-like structures and uptake LDL, respectively. Conclusion: The results indicated that umbilical CL-MSC could differentiate into functional endothelial-like cells. Also, they are suitable for basic and clinical studies to cure several vascular-related diseases. Key Words: Endothelial differentiation, Endothelial-like cells, Mesenchymal stem cells, Umbilical cord lining membrane     

Efficiency of amino acid utilization in the growing pig at suboptimal levels of intake: branched-chain amino acids, histidine and phenylalanine + tyrosine

Five balance experiments on growing pigs were carried out to study the marginal efficiency of utilization of isoleucine, leucine, valine, histidine and phenylalanine + tyrosine and to estimate their requirements for maintenance. Purified diets based on casein and crystalline amino acids as the sole source of N contained graded levels of each amino acid, corresponding to protein accretion rates of 0, 33, 66, 99 and 132 g/day, respectively. All other essential amino acids were given in a 30% excess. N retention increased linearly (p < 0.01) as the dietary concentration of the limiting amino acid increased. Based on linear regression equations relating amino acid deposition in body protein to amino acid intake, marginal efficiencies of ileal digestible amino acid utilization were calculated to be isoleucine - 0.81, leucine - 0.81, valine - 0.82, histidine - 1.17 and phenylalanine + tyrosine - 0.67. Extrapolating the regression equations to zero N retention, the daily requirements of amino acids for N equilibrium were estimated to be (mg/kg0.75) isoleucine - 18, leucine - 33, valine - 23, histidine - 14 and phenylalanine + tyrosine - 43.