Significance of Milk pH in Newborn Infants

Bottle-fed infants do not gain weight as rapidly as breast-fed babies during the first week of life. This weight lag can be corrected by the addition of a small amount of alkali (sodium bicarbonate or trometamol) to the feeds. The alkali corrects the acidity of cow''s milk which now assumes some of the properties of human breast milk. It has a bacteriostatic effect on specific Escherichia coli in vitro, and in infants it produces a stool with a preponderance of lactobacilli over E. coli organisms. When alkali is removed from the milk there is a decrease in the weight of an infant and the stools contain excessive numbers of E. coli bacteria.A pH-corrected milk appears to be more physiological than unaltered cow''s milk and may provide some protection against gastroenteritis in early life. Its bacteriostatic effect on specific E. coli may be of practical significance in feed preparations where terminal sterilization and refrigeration are not available. The study was conducted during the week after birth, and no conclusions are derived for older infants. The long-term effects of trometamol are unknown. No recommendation can be given for the addition of sodium bicarbonate to milks containing a higher content of sodium.     

Contribution of Glucosinolate Transport to Arabidopsis Defense Responses

Accumulation of glucosinolates, a class of defense-related secondary metabolites found almost exclusively in the Capparales, is induced in response to a variety of biological stresses. It is often assumed that elevated glucosinolate levels result from de novo biosynthesis, but glucosinolate transport from other parts of the plant to the site of herbivory or pathogen infection can also contribute to the defense response. Several studies with Arabidopsis and other crucifers have demonstrated that glucosinolates from vegetative tissue are transported to developing seeds. Here we discuss evidence that long-chain aliphatic glucosinolates are transported to the site of herbivory in response to Myzus persicae (green peach aphid) feeding on Arabidopsis.Key Words: glucosinolate, transport, graft, Arabidopsis, Myzus persicae, aphid     

Maintaining functional major histocompatibility complex diversity under inbreeding: the case of a selfing vertebrate

Major histocompatibility complex (MHC) genes encode proteins that present pathogen-derived antigens to T-cells, initiating the adaptive immune response in vertebrates. Although populations with low MHC diversity tend to be more susceptible to pathogens, some bottlenecked populations persist and even increase in numbers despite low MHC diversity. Thus, the relative importance of MHC diversity versus genome-wide variability for the long-term viability of populations after bottlenecks and/or under high inbreeding is controversial. We tested the hypothesis that genome-wide inbreeding (estimated using microsatellites) should be more critical than MHC diversity alone in determining pathogen resistance in the self-fertilizing fish Kryptolebias marmoratus by analysing MHC diversity and parasite loads in natural and laboratory populations with different degrees of inbreeding. Both MHC and neutral diversities were lost after several generations of selfing, but we also found evidence of parasite selection acting on MHC diversity and of non-random loss of alleles, suggesting a possible selective advantage of those individuals with functionally divergent MHC, in accordance with the hypothesis of divergent allele advantage. Moreover, we found that parasite loads were better explained by including MHC diversity in the model than by genome-wide (microsatellites) heterozygosity alone. Our results suggest that immune-related overdominance could be the key in maintaining variables rates of selfing and outcrossing in K. marmoratus and other mixed-mating species.     

Effects of the number of markers per haplotype and clustering of haplotypes on the accuracy of QTL mapping and prediction of genomic breeding values

The aim of this paper was to compare the effect of haplotype definition on the precision of QTL-mapping and on the accuracy of predicted genomic breeding values. In a multiple QTL model using identity-by-descent (IBD) probabilities between haplotypes, various haplotype definitions were tested i.e. including 2, 6, 12 or 20 marker alleles and clustering base haplotypes related with an IBD probability of > 0.55, 0.75 or 0.95. Simulated data contained 1100 animals with known genotypes and phenotypes and 1000 animals with known genotypes and unknown phenotypes. Genomes comprising 3 Morgan were simulated and contained 74 polymorphic QTL and 383 polymorphic SNP markers with an average r² value of 0.14 between adjacent markers. The total number of haplotypes decreased up to 50% when the window size was increased from two to 20 markers and decreased by at least 50% when haplotypes related with an IBD probability of > 0.55 instead of > 0.95 were clustered. An intermediate window size led to more precise QTL mapping. Window size and clustering had a limited effect on the accuracy of predicted total breeding values, ranging from 0.79 to 0.81. Our conclusion is that different optimal window sizes should be used in QTL-mapping versus genome-wide breeding value prediction.     

Novel Escherichia coli umuD′ Mutants: Structure-Function Insights into SOS Mutagenesis

Although it has been 10 years since the discovery that the Escherichia coli UmuD protein undergoes a RecA-mediated cleavage reaction to generate mutagenically active UmuD′, the function of UmuD′ has yet to be determined. In an attempt to elucidate the role of UmuD′ in SOS mutagenesis, we have utilized a colorimetric papillation assay to screen for mutants of a hydroxylamine-treated, low-copy-number umuD′ plasmid that are unable to promote SOS-dependent spontaneous mutagenesis. Using such an approach, we have identified 14 independent umuD′ mutants. Analysis of these mutants revealed that two resulted from promoter changes which reduced the expression of wild-type UmuD′, three were nonsense mutations that resulted in a truncated UmuD′ protein, and the remaining nine were missense alterations. In addition to the hydroxylamine-generated mutants, we have subcloned the mutations found in three chromosomal umuD1, umuD44, and umuD77 alleles into umuD′. All 17 umuD′ mutants resulted in lower levels of SOS-dependent spontaneous mutagenesis but varied in the extent to which they promoted methyl methanesulfonate-induced mutagenesis. We have attempted to correlate these phenotypes with the potential effect of each mutation on the recently described structure of UmuD′.     

Direct immobilization of gangliosides onto gold-carboxymethyldextran sensor surfaces by hydrophobic interaction: applications to antibody characterization

We describe a novel immobilization technique to investigate interactions between immobilized gangliosides (GD3, GM1, and GM2) and their respective antibodies, antibody fragments, or binding partners using an optical biosensor. Immobilization was performed by direct injection onto a carboxymethyldextran sensor chip and did not require derivatization of the sensor surface or the ganglioside. The ganglioside appeared to bind to the sensor surface by hydrophobic interaction, leaving the carbohydrate epitope available for antibody or, in the case of GM1, cholera toxin binding. The carboxyl group of the dextran chains on the sensor surface did not appear to be involved in the immobilization as evidenced by equivalent levels of immobilization following conversion of the carboxyl groups into acyl amino esters, but rather the dextran layer provided a hydrophilic coverage of the sensor chip which was essential to prevent nonspecific binding. This technique gave better reactivity and specificity for anti- ganglioside monoclonal antibodies (anti-GD3: KM871, KM641, R24; and anti-GM2: KM966) than immobilization by hydrophobic interaction onto a gold sensor surface or photoactivated cross-linking onto carboxymethydextran. This rapid immobilization procedure has facilitated detailed kinetic analysis of ganglioside/antibody interactions, with the surface remaining viable for a large number of cycles (>125). Kinetic constants were determined from the biosensor data using linear regression, nonlinear least squares and equilibrium analysis. The values of kd, ka, and KAobtained by nonlinear analysis (KAKM871 = 1.05, KM641 = 1.66, R24 = 0.14, and KM966 = 0.65 x 10(7) M- 1) were essentially independent of concentration and showed good agreement with data obtained by other analytical methods.      

Biochemistry and structure of the glycan secreted by desiccation-tolerantNostoc commune (Cyanobacteria)

Summary Filaments of the desiccation-tolerant cyanobacteriumNostoc commune are embedded within, and distributed throughout, a dense glycan sheath. Analysis of the glycan of field materials and of pure cultures ofN. commune DRH 1 through light and electron microscopy, immunogold labelling and staining with dyes, revealed changes in the pattern of differentiation in glycan micro-structure, as well as localized shifts in pH, upon rehydration of desiccated field material. A Ca/Si rich external (pellicular) layer of the glycan acts as a physical barrier to epiphytic bacteria on the surface ofN. commune colonies. A purified fraction (>12 kDa) of an aqueous extract of the glycan from desiccated field material contained glucose, N-acetylglucosamine, glucosamine, mannose, and galactosamine with ratios of 3.11.410.10.06, respectively. Lipid soluble extracts ofN. commune contained trehalose and sucrose and the levels of both became undetectable following cell rehydration. Intracellular cyanobacterial trehalase was identified using immunoblotting and its synthesis was detected upon rehydration of desiccated field cultures. Elemental analysis of glycan extracts showed a flux in the concentrations of salts in the glycan matrix following rehydration of desiccated colonies. Water-stress proteins (Wsp; most abundant proteins in glycan), a water soluble UV-A/B-absorbing pigment, the lipid-soluble UV-protective pigment scytonemin (in both its oxidized and reduced forms), as well as two unidentified cyanobacterial glycoproteins (75 kDa and 110 kDa), were found within the glycan matrix. An unidentified 68 kDa protein, the second most abundant protein in aqueous extracts of the glycan, was isolated and its N-terminal sequence was determined as AFIFGTISPNNLSGTSGNSGIVGSA. Gene bank searches with this sequence identified significant homologies (35–45%) with various carbohydrate-modifying enzymes. The role of the glycan in the desiccation tolerance ofN. commune is discussed with respect to structure/function relationships.Abbreviations EPS extracellular polysaccharides - Wsp water-stress protein - SEM scanning electron microscopy - TEM transmission electron microscopy - EDX energy dispersive X-ray analysis - FPLC fast performance liquid chromatography - SDS-PAGE sodium dodecylsulfate polyacrylamide gel electrophoresis - TLC thin layer chromatography - UV ultra-violet radiation - UTEX University of Texas Culture Collection     

The role of nitric oxide in the regulation of the systemic and pulmonary vasculature of the rattlesnake, <Emphasis Type="Italic">Crotalus durissus terrificus</Emphasis>

The functional role of nitric oxide (NO) was investigated in the systemic and pulmonary circulations of the South American rattlesnake, Crotalus durissus terrificus. Bolus, intra-arterial injections of the NO donor, sodium nitroprusside (SNP) caused a significant systemic vasodilatation resulting in a reduction in systemic resistance (Rsys). This response was accompanied by a significant decrease in systemic pressure and a rise in systemic blood flow. Pulmonary resistance (Rpul) remained constant while pulmonary pressure (Ppul) and pulmonary blood flow (Qpul) decreased. Injection of L-Arginine (L-Arg) produced a similar response to SNP in the systemic circulation, inducing an immediate systemic vasodilatation, while Rpul was unaffected. Blockade of NO synthesis via the nitric oxide synthase inhibitor, L-NAME, did not affect haemodynamic variables in the systemic circulation, indicating a small contribution of NO to the basal regulation of systemic vascular resistance. Similarly, Rpul and Qpul remained unchanged, although there was a significant rise in Ppul. Via injection of SNP, this study clearly demonstrates that NO causes a systemic vasodilatation in the rattlesnake, indicating that NO may contribute in the regulation of systemic vascular resistance. In contrast, the pulmonary vasculature seems far less responsive to NO.     

Conservation biogeography of the Antarctic

Aim

To present a synthesis of past biogeographic analyses and a new approach based on spatially explicit biodiversity information for the Antarctic region to identify biologically distinct areas in need of representation in a protected area network.

Location

Antarctica and the sub‐Antarctic.

Methods

We reviewed and summarized published biogeographic studies of the Antarctic. We then developed a biogeographic classification for terrestrial conservation planning in Antarctica by combining the most comprehensive source of Antarctic biodiversity data available with three spatial frameworks: (1) a 200‐km grid, (2) a set of areas based on physical parameters known as the environmental domains of Antarctica and (3) expert‐defined bioregions. We used these frameworks, or combinations thereof, together with multivariate techniques to identify biologically distinct areas.

Results

Early studies of continental Antarctica typically described broad bioregions, with the Antarctic Peninsula usually identified as biologically distinct from continental Antarctica; later studies suggested a more complex biogeography. Increasing complexity also characterizes the sub‐Antarctic and marine realms, with differences among studies often attributable to the focal taxa. Using the most comprehensive terrestrial data available and by combining the groups formed by the environmental domains and expert‐defined bioregions, we were able to identify 15 biologically distinct, ice‐free, Antarctic Conservation Biogeographic Regions (ACBRs), encompassing the continent and close lying islands.

Main conclusions

Ice‐free terrestrial Antarctica comprises several distinct bioregions that are not fully represented in the current Antarctic Specially Protected Area network. Biosecurity measures between these ACBRs should also be developed to prevent biotic homogenization in the region.