Phylogeny ofRubiaceae-Rubieae inferred from the sequence of a cpDNA intergene region

A phylogenetic analysis of 25 species, representing eight genera of theRubieae tribe (Rubiaceae), has been made using the DNA sequence of the chloroplastatp B-rbc L intergene region. Six tropical genera from other tribes ofRubiaceae have been used as outgroups. Whatever the method of analysis (distance, parsimony or maximum likelihood), five groups are clearly separated and described as informal clades. Their relative relationships are not clearly resolved by the parsimony analysis, resulting in eight equally parsimonious trees, 327 steps long, with a consistency index (CI) of 0.749 (excluding uninformative sites). TheRubieae tribe appears monophyletic from the data available. Some new and partly unexpected phylogenetic relationships are suggested. The genusRubia forms a separate clade and appears to be the relatively advanced sister group of the remaining taxa. TheSherardia clade also includes the generaCrucianella andPhuopsis. Galium sect.Aparinoides appears closely attached to theAsperula sect.Glabella clade. The remaining taxa ofGalium are paraphyletic:Galium sect.Platygalium (in theCruciata clade) is linked to the advanced generaCruciata andValantia; the more apomorphic groups ofGalium form theGalium sect.Galium clade, including the perennial sectionsGalium, Leiogalium, andLeptogalium as well as the annual (and possibly polyphyletic) sect.Kolgyda.     

cpDNA intergene sequences corroborate restriction site data for reconstructingRubiaceae phylogeny

Representatives of seven genera from five tribes ofRubiaceae have been compared in respect to a non-coding intergene cpDNA region of about 1000 bp, situated between the atpB and the rbcL genes. The resulting most parsimonious PAUP cladogram corresponds very well with one based on total cpDNA restriction site data obtained byBremer & Jansen (1991). The two different molecular analyses thus corroborate each other and contribute to an improved systematic arrangement of the large family, e.g., in respect to placing the tribeHedyotideae clearly into the subfamilyRubioideae, closer toRubieae than toPsychotrieae.     

Importance of fungi in the diet of Gammarus pulex and Asellus aquaticus

An important component of the interaction between macroinvertebrates and leaf litter in streams in the extent to which consumers can differentiate between undecomposed and decomposing leaves. The detritivores Gammarus pulex and Asellus aquaticus fed preferentially on conditioned rather on unconditioned leaf material. Growth in A. aquaticus was significantly reduced when unconditioned leaves were provided, but in G. pulex no significant effect of conditioning on growth was observed. The capacity of G. pulex to tolerate reductions in food quality seems to be a consequence of a compensatory system in which respiration rates change to compensate for reductions in food quality. In this way a constant growth rate is maintained. Increases in ingestion rates to compensate for low quality food were not observed.     

Genotypic variation in biological nitrogen fixation by common bean

Field experiments were performed in Austria, Brazil, Chile, Colombia, Guatemala, Mexico and Peru as part of an FAO/IAEA Co-ordinated Research Programme to investigate the nitrogen fixing potential of cultivars and breeding lines of common bean (Phaseolus vulgaris L.). Each experiment included approximately 20 bean genotypes which were compared using the ¹⁵N isotope dilution method. Great differences in nitrogen fixation were observed between and within experiments, with average values of 35% N derived from atmosphere (% Ndfa) and highest values of 70% Ndfa being observed. These values which were larger than had been reported previously for common bean, were observed only when environmental factors were favorable. Therefore, common bean lines are available, which can support high biological nitrogen fixation. These can be used either directly as cultivars for production or in breeding programmes to enhance nitrogen fixation in other cultivars.     

Cobalt determination in serum and urine by electrothermal atomic absorption spectrometry

Cobalt determinations in biological fluids are of great interest in biological or toxicological research programs. Cobalturia is often chosen as an indicator for a biological monitoring program in occupational exposure to cobalt dusts. The method described here derives from the IUPAC reference method for nickel determination. It enables cobaltemia and cobalturia to be measured in small samples (1 mL). The mean usual values for cobalt in biological fluids are very low (2.7 nmol L⁻¹ for serum and 6.7 nmol L⁻¹ for urine), and therefore, thus require an analytical procedure with preconcentration and extraction. The sample is mineralized by wet acid digestion. After digestion, inorganic cobalt is extracted in form of ammonium pyrrolidine dithiocarbamate complex into isobutyl methyl ketone and measured in the organic layer by electrothermal atomic absorption spectrometry. The analytical parameters are described in detail. The extraction output is about 99%. The detection limits are 1.93 and 1.89 nmol L⁻¹ for serum and urine, respectively. Sensitivity (expressed as the concentration that gives a 0.044 absorbance) is 3.4 nmol L⁻¹ for serum and 3.3 nmol L⁻¹ for urine. Within-run precision ranged between 3.9 and 2.5% (coefficients of variation) for serum and 4.2 and 1.1% for urine, at 87 and 136 nmol L⁻¹ levels, respectively. Between-run precision ranged between 4.3 and 3.3% (coefficients of variation) for serum and 4.2 and 2.3% for urine, at 87 and 136 nmol L⁻¹ levels, respectively. At very low concentration, 5.7 nmol L⁻¹ for serum and 2.5 nmol L⁻¹ for urine, the between-run precision is, respectively, 19.5 and 28%. Linearity is effective between 0 and 272 nmol L⁻¹. Interferences and matrix effects are negligible for urine, serum, or plasma samples without hemoglobin. The method is easily applicable for routine determinations.     

Amplified somatic embryogenesis from male flowers of triploid banana and plantain cultivars (Musa spp.)

Summary Somatic embryogenesis and plant regeneration of banana and plantain cultivars (Musa spp.) were obtained by culturing young male flowers. Multiplication and maintenance of embryogenic cultures were achieved by culturing somatic embryos in a temporary immersion system (SIT). A multiplication rate of 40 allowed us to obtain more than 6000 somatic embryos after 6 mo. of subculture. Plant recovery frequencies were 60 to 70%. This method was expanded to different banana and plantain genomic groups.     

Seed protein and isozyme variations in Triticum tauschii (Aegilops squarrosa)

Sixty Triticum tauschii (Aegilops squarrosa, 2n=2x=14, DD) accessions were evaluated for the variability of high-molecular-weight (HMW) glutenins, gliadins and isozymes of seed esterase, -amylase and glucose-phosphate isomerase. Wide variability was observed for HMW-glutenins and gliadins. The implications of unique HMW-glutenin alleles for quality parameters are discussed. Isozyme evaluations indicated more variability for the Est-D ^t 5 locus as compared to the Est-D5 of bread-wheat. The polymorphism for -Amy-D ^t 1 was less than that of -Amy-D1. Similar to the bread-wheat situation, Gpi-D ^t 1 showed no polymorphism. The variability observed with the traits evaluated can be readily observed in T. turgidum x T. tauschii synthetic hexaploids (2n=6x=42, AABBDD) suggesting that T. tauschii accessions may be a rich source for enhancing the genetic variability of T. aestivum cultivars.     

Dialysable leukocyte extracts modify the course of experimental paracoccidioidomycosis in the Syrian hamster

The effect of dialysable leukocyte extracts (DLE) obtained from hamsters immunized withParacoccidioides brasiliensis (immune DLE) and from non-immunized hamsters (non-immune DLE) was studied in hamsters inoculated withP. brasiliensis by the intratesticular route. Treatment with immune or non-immune DLE was started during the third week of infection and was repeated at 7, 11, 15 and 19 weeks. A group of untreated infected animals was used as control. Animals were submitted to the delayed hypersensitivity skin test toP. brasiliensis antigen (PbAg) in vivo and assayed in vitro by the macrophage migration inhibition test in the presence of Phytohemagglutinin (PHA) and PbAg and by immunodiffusion for specific antibody. The animals were sacrificed at 4, 8, 12, 16 and 20 weeks. The morphology and extension of the lesions were studied at the inoculation site, and in lymph nodes, lungs, liver, spleen and kidneys. In contrast to the controls, animals treated with both DLEs maintained a positive cell-mediated immune response throughout the experiment and developed less extensive infection with a significantly lower number of fungi in the lesions. The results suggest that immune and non-immune DLE preparations modified the evolution of experimental paracoccidioidomycosis with equal efficiency. This similarity may be explained by the immunoregulatory activities of both extracts.     

Identification of a developmentally regulated sialidase inEimeria tenella that is immunologically related to theTrypanosoma cruzi enzyme

Sporozoites and merozoites of three species ofEimeria, E. tenella, E. maxima, andE. necatrix, that cause diarrhea in chickens worldwide, were examined for their expression of sialidase (SA) activity. The enzyme was found in three species, and the activity of merozoites was 10–20 times higher than that of sporozoites. The enzyme was resistant to degradation by proteases that are normally present in the intestine, a site inhabited by theEimeria parasites, and it was relatively resistant to heat, with optimum activity being at 40°C, which is within the range of temperature in the chicken intestine (40–43°C).E. tenella SA was immuniprecipitated by monoclonal and polyclonal antibodies raised against theTrypanosoma cruzi SA (TCSA), and enzyme activity was neutralized by these antibodies.E. tenella SA was identified by immunoblots as a doublet of molecular weight 190 000 and 180 000 using, as a probe, anti-TCSA antibodies and antibodies against a synthetic peptide (TR) derived from the long tandem repeat domain of TCSA. Binding of the monoclonal and polyclonal antibodies toE. tenella was completely blocked by TR, but not by an irrelevant peptide (BR). Therefore,E. tenella expresses a developmentally regulated SA that is structurally related to theT. cruzi counterpart. Because of the high SA activity in merozoites, and by analogy with other SA-producing microbes that inhabit mucin-rich epithelia, we suggest that theEimeria SA plays a role in desialylating intestinal mucins to reduce viscosity of the local environment and thereby facilitate parasite migration. The enzyme could also play a role in host cell-parasite interaction.Abbreviations SA sialidase (neuraminidase) - Neu5Ac N-acetylneuraminic acid - 4-MU-Neu5Ac 2-(4-methylumbelliferyl)--N-acetyl-d-neuraminic acid - BSA bovine serum albumin - PBS phosphate buffered saline - PMSF phenylmethylsulfonyl fluoride - PNA peanut agglutinin - Ab antibody - TCN-2 monoclonal antibody toT. cruzi sialidase, anti-Ars, monoclonal antibody top-azophenylarsonate - TCSA Trypanosoma cruzi sialidase     

Prospects for the genetics of human longevity

Longevity varies between and within species. The existence of species-specific limit to human life-span and its partial heritability indicate the existence of genetic factors that influence the ageing process. Insight into the nature of these genetic factors is provided by evolutionary studies, notably the disposable soma theory, which suggests a central role of energy metabolism in determining life-span. Energy is important in two ways. First, the disposable soma theory indicates that the optimum energy investment in cell maintenance and repair processes will be tuned through natural selection to provide adequate, but not excessive, protection against random molecular damages (e.g. to DNA, proteins). All that is required is that the organism remains in a sound condition through its natural expectation of life in the wild environment, where accidents are the predominant cause of mortality. Secondly, energy is implicated because of the intrinsic vulnerability of mitochondria to damage that may interfere with the normal supply of energy to the cell via the oxidative phosphorylation pathways. Oxidative phosphorylation produces ATP, and as a by-product also produces highly reactive oxygen radicals that can damage many cell structures, including the mitochondria themselves. Several lines of evidence link, on the one hand, oxidative damage to cell ageing, and on the other hand, energy-dependent antioxidant defences to the preservation of cellular homeostasis, and hence, longevity. Models of cellular ageing in vitro allow direct investigation of mechanisms, such as oxidative damage, that contribute to limiting human life-span. The genetic substratum of inter-individual differences in longevity may be unraveled by a two-pronged reverse genetics approach: sibling pair analysis applied to nonagenarian and centenarian siblings, combined with association studies of centenarians, may lead to the identification of genetic influences upon human longevity. These studies have become practicable thanks to recent progress in human genome mapping, especially to the development of microsatellite markers and the integration of genetic and physical maps.