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The main objective of this analytical overview is to assess the validity of maternal perception of the onset of lactation (OL) as an indicator of lactogenesis stage II (LS-II). Prospective studies that assessed OL and/or LS-II [based on test-weighing milk volume (MV) and/or breast milk biomarkers (BMB)] were identified. OL is a clearly defined and easily identified event across cultures, with the overwhelming majority of women being able to report when they experience it. Mean OL ranges from 50 to 73 h postpartum across studies and from 1 to 148 h postpartum within studies. The wide range detected within samples is fully consistent with the wide within sample LS-II variability as determined by BMB or MV. Studies have identified similar risk factors for delayed LS-II, such as labor and delivery stress, primiparity and insulin-dependent diabetes mellitus, regardless of marker used (i.e., OL, MV or BMB). The correlation between OL and MV (r = -0.60) is of similar magnitude to that between OL and BMB (r = 0.50) and that between BMB and MV (r = 0.47-0.69). In conclusion, OL is a valid clinical indicator of LS-II. This has public health relevance because studies have identified delayed OL (i.e., >72 h postpartum) as a risk factor for shorter breastfeeding duration and for greater infant weight loss by d 3 postpartum. Multidisciplinary studies are needed to standardize the definition of OL and to confirm its validity in different sociocultural contexts. [ABSTRACT FROM AUTHOR]

Test weighing is the "gold standard" for documenting lactogenesis stage II. However, this method is impractical for use in population studies. Maternal perception of the timing of the onset of lactation may be a useful proxy for lactogenesis stage II. This study seeks to validate maternal perception of the onset of lactation as a marker of lactogenesis stage II. Women (n = 60) were recruited after cesarean delivery. Beginning at 24 h postpartum (pp), the onset of lactation was assessed 3 times daily by both test weighing and maternal perception. Delayed onset of lactation was defined as follows: 1) milk transfer < 9.2 g/feeding at 60 h pp and 2) maternal perception >/= 72 h pp. Misclassification analyses were conducted. Multivariate logistic regression, bivariate analyses and Cox survival analyses were used to evaluate the determinants and consequences of delayed onset of lactation, using both definitions. The sensitivity and specificity of delayed maternal perception as an indicator of delayed lactogenesis were 71.4 and 79.3%, respectively. Four risk factors for low milk transfer were significant (P: < 0.05) or nearly significant (P:

Photosystem 2 reaction centre complexes prepared either by solubilisation with Triton X-100 and subsequent exchange into dodecyl maltoside or by a procedure involving a combination of dodecyl maltoside and LiClO4, were characterised in terms of chlorophyll a, pheophytin a, beta-carotene and cytochrome b559 content. Time-resolved chlorophyll fluorescence decay kinetics were measured using both types of complexes. Our data show that the isolated photosystem two reaction centre complex contain, for two pheophytin a molecules, close to six chlorophyll a, two beta-carotene and one cytochrome b559. No major differences were observed in the composition or the kinetic characteristics measured in the samples prepared by the different procedures. Time-resolved fluorescence measurements indicate that more than 94% of the chlorophyll a in both preparations is coupled to the reaction centre complex.

The effects of temporal (among different branches of a phylogeny) and spatial (among different nucleotide sites within a gene) nonuniformities of nucleotide substitution rates on the construction of phylogenetic trees from nucleotide sequences are addressed. Spatial nonuniformity may be estimated by using Shannon's (1948) entropy formula to measure the Relative Nucleotide Variability (RNV) at each nucleotide site in an aligned set of sequences; this is demonstrated by a comparative analysis of 5S rRNAs. New methods of constructing phylogenetic trees are proposed that augment the Unweighted Pair-Group Using Arithmetic Averages (UPGMA) algorithm by estimating and compensating for both spatial and temporal nonuniformity in substitution rates. These methods are evaluated by computer simulations of 5S rRNA evolution that include both kinds of nonuniformities. It was found that the proposed Reference Ratio Method improved both the ability to reconstruct the correct topology of a tree and also the estimation of branch lengths as compared to UPGMA. A previous method (Farris et al. 1970; Klotz et al. 1979; Li 1981) was found to be less successful in reconstructing topologies when there is high probability of multiple mutations at some sites. Phylogenetic analyses of 5S rRNA sequences support the endosymbiotic origins of both chloroplasts and mitochondria, even though the latter exhibit an accelerated rate of nucleotide substitution. Phylogenetic trees also reveal an adaptive radiation within the eubacteria and another within the eukaryotes for the origins of most major phyla within each group during the Precambrian era.

Cross reactivity of prednisolone with an antiserum raised against dexamethasone-21-hemisuccinate conjugated with bovine serum albumin was utilized to develop a radioimmunoassay for prednisolone in unextracted plasma. The results are in good agreement with those obtained with a standard competitive protein binding method employing prior extraction and separation of the synthetic from endogenous steroids.

The lipid composition and level of unsaturation of fatty acids has been determined for chloroplast thylakoid membranes isolated from Pisum sativum grown under cold (4 degrees /7 degrees C) or warm (14 degrees /17 degrees C) conditions. Both the relative amounts of lipid classes and degree of saturation were not greatly changed for the two growth conditions. In cold-grown plants, there was a slightly higher linolenic and lower linoleic acid content for the glycolipids monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol. In contrast to thylakoid membranes, a non-thylakoid leaf membrane fraction including the chloroplast envelope, had a higher overall level of fatty acid unsaturation in cold-grown plants due mainly to an increase in the linolenic acid content of MGDG, DGDG, phosphatidylglycerol, and phosphatidylcholine. The most clear cut change in the thylakoid membrane composition was the lipid to protein ratio which was higher in the cold-grown plants.

The biosynthesis of 4-hydroxybenzaldehyde and 3-bromo-4-hydroxybenzaldehyde from l-[U-(14)C]tyrosine has been demonstrated in chloroplast-containing fractions obtained by differential and isopycnic centrifugation from the marine red alga Odonthalia floccosa. Surfactant and high speed centrifugation studies indicate that the biosynthetic pathway involves a particulate enzyme system, possibly located on the thylakoid membranes. The following scheme, based upon identification of labeled (14)C-intermediates, is proposed for the formation of aldehydes: l-tyrosine --> 4-hydroxyphenylpyruvic acid --> 4-hydroxyphenylacetic acid --> 4-hydroxymandelic acid --> 4-hydroxybenzaldehyde --> 3-bromo-4-hydroxybenzaldehyde.

Leaves of Vicia faba were fed (14)CO(2) in light for periods of up to 6 hours. At intervals, leaf samples were homogenized and separated into fractions which contained "broken" and "intact" chloroplasts, and three other high speed centrifugal fractions containing other cell membranes and chloroplast envelopes. Analyses of the radioactive labeling of galactose from the galactolipids in these fractions and in purified chloroplast envelopes indicated that the major site of galactosyl transferase enzyme activity was in the chloroplast envelope. The data suggest that in time much of the radioactive galactolipid was transferred from the envelope to the thylakoid-containing fractions. The major site of galactolipid synthesis appears to be in the envelope but there is some evidence of another site in the thylakoids.

The concentrations of free amino acids and amides within isolated maize (Zea mays L.) plastids were determined and compared with concentrations in the leaf tissue. The concentrations were different for each individual amino acid and varied between 1 and 10 millimolar. At five different developmental stages concentrations in the plastids were greater than those in the intact leaf tissue. During development, from the proplastid stage to the mature chloroplast, the amount of each amino acid per plastid remained relatively constant, but there were decreases in concentrations of plastid amino acids resulting from the developmental increase in plastid volume. In proplastids, the free amino acids were present in greater concentrations than those previously found to inhibit partially amino acid-synthesizing enzymes located in chloroplasts. In the chloroplasts, the molarities of the free amino acids were within the range known to inhibit amino acid-synthesizing enzymes.