Inefficient Degradation of Oxidized Regions of Protein Molecules

We have previously shown that the intracellular half-life of endocytosed oxidized albumin is much longer than that of native albumin. We now report that the regions of oxidized albumin which contain oxidation products (carbonyls and fluorophores), are less readily released as small degradation products by cell-free proteolysis than is the molecule overall. We deduce that oxidized moieties in the polypeptide chain can confer localized resistance to enzymatic proteolysis. Such resistance to proteolysis may account for the intracellular accumulation of some endocytosed oxidized protein which we have previously observed.     

Deletion breakpoints associated with the Prader-Willi and Angelman syndromes (15q11-q13) are not sites of high homologous recombination

Deletions of 15q11.2-q12 are associated with either the Prader-Willi (PWS) or Angelman (AS) syndromes. It has been suggested that excessive recombination in this region might explain the high frequency of such deletions, and the frequent involvement of chromosome 15 in translocations and nondisjunction. We have studied recombination in the PWS region by linkage analysis of non-PWS families. No recombination was found (with maximum lod scores greater than 3.0) for most pairwise combinations of probes: 39, IR4-3R, ML34, 189-1, 3-21. A hotspot of recombination is observed between loci detected by p3-21 and pIR10-1. The female recombination fraction in this region was significantly higher than that for males. Close linkage with 0.06 recombination was found for the IR10-1 and CMW-1 pair. No excess recombination was found between sites bounding common breakpoints observed in deletions associated with PWS and AS. It is suggested that these deletions form frequently because of the presence of duplicated DNA sequences and/or inversions in this region, and not because of a high rate of homologous recombination.     

Molecular analyses of turf algae reveal a new species and an undetected introduction in the Pterosiphonieae (Rhodomelaceae,Rhodophyta)

Introduced seaweeds and undescribed species often remain undetected because marine regional floras are as yet poorly understood. DNA sequencing facilitates their detection, but databases are incomplete, so their improvement will continue to lead the discovery of these species. Here we aim to clarify the taxonomy of two turf-forming red algal Australian species that morphologically resemble the European Aphanocladia stichidiosa. We also aim to elucidate whether either of these species could have been introduced in Europe or Australia. We studied their morphology, analyzed 17 rbcL sequences of European and Australian specimens, examined their generic assignment using a phylogeny based on 24 plastid genomes, and investigated their biogeography using a taxon-rich phylogeny including 52 rbcL sequences of species in the Pterosiphonieae. The rbcL sequences of one of the Australian species were identical to A. stichidiosa from Europe, considerably expanding its known distribution. Unexpectedly, our phylogenetic analyses resolved this species in the Lophurella clade rather than in Aphanocladia and the new combination L. stichidiosa is proposed. The other Australian species is described as L. pseudocorticata sp. nov. Although L. stichidiosa was originally described in the Mediterranean ca. 70 years ago, our phylogenetic analyses placed it in a lineage restricted to the southern hemisphere, showing that it is native to Australia and introduced to Europe. This study confirms that further work using molecular tools is needed to characterize seaweed diversity, especially among the poorly explored algal turfs, and showcases the usefulness of phylogenetic approaches to uncover introduced species and to determine their native ranges.     

Multicolor FISH Mapping with Alu-PCR-Amplified YAC Clone DNA Determines the Order of Markers in the BRCA1 Region on Chromosome 17q12-q21

A gene designated BRCA1, implicated in the susceptibility to early-onset familial breast cancer, has recently been localized to chromosome 17q12-q21. To date, the order of DNA markers mapped within this region has been based on genetic linkage analysis. We report the use of multicolor fluorescence in situ hybridization to establish a physically based map of five polymorphic DNA markers and 10 cloned genes spanning this region. Three cosmid clones and Alu-PCR-generated products derived from 12 yeast artificial chromosome clones representing each of these markers were used in two-color mapping experiments to determine an initial proximity of markers relative to each other on metaphase chromosomes. Interphase mapping was then employed to determine the order and orientation of closely spaced loci by direct visualization of fluorescent signals following hybridization of three probes, each detected in a different color. Statistical analysis of the combined data suggests that the order of markers in the BRCA1 region is cen-THRA1-TOP2-GAS-OF2-17HSI)-248yg9-RNU2-OF3-PPY/p131-EPB3-Mfd188-WNT3-HOX2-GP3A-tel. This map is consistent with that determined by radiation-reduced hybrid mapping and will facilitate positional cloning strategies in efforts to isolate and characterize the BRCA1 gene.     

Molecular evidence on Primate phylogeny from DNA sequences

Evidence from DNA sequences on the phylogenetic systematics of primates is congruent with the evidence from morphology in grouping Cercopithecoidea (Old World monkeys) and Hominoidea (apes and humans) into Catarrhini, Catarrhini and Platyrrhini (ceboids or New World monkeys) into Anthropoidea, Lemuriformes and Lorisiformes into Strepsirhini, and Anthropoidea, Tarsioidea, and Strepsirhini into Primates. With regard to the problematic relationships of Tarsioidea, DNA sequences group it with Anthropoidea into Haplorhini. In addition, the DNA evidence favors retaining Cheirogaleidae within Lemuriformes in contrast to some morphological studies that favor placing Cheirogaleids in Lorisiformes. While parsimony analysis of the present DNA sequence data provides only modest support for Haplorhini as a monophyletic taxon, it provides very strong support for Hominoidea, Catarrhini, Anthropoidea, and Strepsirhini as monophyletic taxa. The parsimony DNA evidence also rejects the hypothesis that megabats are the sister group of either Primates or Dermoptera (flying lemur) or a Primate-Dermoptera clade and instead strongly supports the monophyly of Chiroptera, with megabats grouping with microbats at considerable distance from Primates. In contrast to the confused morphological picture of sister group relationships within Hominoidea, orthologous noncoding DNA sequences (spanning alignments involving as many as 20,000 base positions) now provide by the parsimony criterion highly significant evidence for the sister group relationships defined by a cladistic classification that groups the lineages to all extant hominoids into family Hominidae, divides this ape family into subfamilies Hylobatinae (gibbons) and Homininae, divides Homininae into tribes Pongini (orangutans) and Hominini, and divides Hominini into subtribes Gorillina (gorillas) and Hominina (humans and chimpanzees). A likelihood analysis of the largest body of these noncoding orthologues and counts of putative synapomorphies using the full range of sequence data from mitochondrial and nuclear genomes also find that humans and chimpanzees share the longest common ancestry. © 1994 Wiley-Liss, Inc.     

Observations on the structure of kefir grains and the distribution of the microflora

The mixed flora of yeasts and lactobacilli of kefir is held together in non-dispersible structures which build up into large grains. The fibrillar extracellular material of the matrix in which the microflora is embedded was stained by ruthenium red and periodic acid-thiosemicarbazide silver proteinate, indicating that it was largely composed of carbohydrate. It is suggested that the carbohydrate is of bacterial origin and that this is produced by a population of lactobacilli which resides within the matrix and which separates non-carbohydrate-producing populations of lactobacilli and yeasts so that sheet-like structures are formed which show asymmetry, with yeasts predominating on one side and lactobacilli on the other.     

Physiologic and environmental factors influencing the calcium-to-tissue ratio in populations of three species of freshwater pulmonate snails

Summary A study of three species of freshwater pulmonate snails, Physa gyrina (11 populations), Physa integra (17 populations), and Helisoma anceps (18 populations) was carried out from 1973 to 1976, primarily in Michigan.The ratio of whole animal calcium content to tissue dry weight (Ca: tissue ratio) changes with age, but these changes are largely restricted to early growth and do not significantly affect individuals over 40 mg total dry weight, regardless of species.Parasitization by larval trematodes was found to have no significant effect on the Ca: tissue ratio in the populations examined regardless of species.Ca: tissue ratio of P. gyrina did not vary greatly between populations and showed a narrow range over a wide range of environmental calcium concentrations. Shell mass in P. gyrina is therefore either physiologically regulated in all populations (at a species specific constant level) or interpopulation variation is minimized by moderately high levels of gene flow between populations.There was no relationship between Ca: tissue ratio and environmental calcium for either P. integra or H. anceps over a wide range of snail and environmental calcium values. In both of the foregoing species, shell calcium content varied greatly between populations. This variation did not conform to any apparent geographic cline.In 7 of the population sites studied, P. integra and H. anceps coexist, and when these sites are listed from highest to lowest Ca: tissue ratios, the rank orders for the two species are nearly identical. This suggests that there is some environmental factor (possibly trophic conditions) at these localities that influences shell mass.In 8 other species of pulmonates briefly examined, differences in Ca: tissue ratio between populations of the same species were often as great as or greater than differences between species.While the patterns of shell mass and environmental calcium for these species are not unlike those previously reported, the proposed causal factors for these patterns are clearly distinct from those suggested for other freshwater pulmonates.     

An analysis of chewed food particle size and its relationship to molar structure in the primatesCheirogaleus medius andGalago senegalensis and the insectivoranTupaia glis

The chewed food particle size and shearing capacity of the lower molars of two primate species, the fat-tailed dwarf lemur,Cheirogaleus medius and the bushbabyGalago senegalensis, and an insectivoran, the tree shrew,Tupaia glis, were compared. Differences in the shearing design of the lower molars correlate strongly with the chewed food particle size in these species: the greater the shearing capacity, the smaller the chewed food particles. These three species are of comparable size but differ greatly in diet in the wild.C. medius primarily eats fruit and nectar, whileG. senegalensis andT. glis are largely insect-eaters. The lower molars ofG. senegalensis andT. glis show a much greater shearing capacity than do those ofC. medius. The average length of chewed food particles ofC. medius is significantly larger than that ofG. senegalensis, while that ofT. glis is intermediate between the two primates but is closer to that ofG. senegalensis. Our findings that insect-eating species grind their food more finely than do fruit- and resin-eating species can be correlated with digestibility of foods: finely chewing foods such as fruits which are low in relatively undigestible cell wall components would not greatly improve their digestibility, so a highly efficient food processing apparatus would be less important to the animal's survival. Insect-eaters much more finely chew their foods, implying that there is some constituent of insect bodies difficult to digest, and that grinding increases its digestibility. We suggest that this constituent is chitin.     

KINEMATICS OF HYPOCOTYL CURVATURE

Time lapse photographs were analyzed for curvature, κ, of the plumular hook as a function of distance from the apex, s, of seedlings of lettuce. Lactuca sativa cv ‘Grand Rapids,‘ during hook maintenance (red light) and hook opening (white light). Curvature of the inner edge of the photographic projection of the hook increases from 0.14 mm^–1 near the apex to 12.7 mm^–1 at the hook bisector (about 1 mm from the apex) and decreases to approximately zero below the hook (2 mm from the apex). Using concepts from fluid dynamics we relate growth rates to curvature changes. For a material element of stem cross section located at s we predict that where M(s,o) and M(s,i) are the relative elemental growth rates at the outer and inner edges of the hypocotyl cross section, w is element width, t is time, and u(s) is velocity of departure of s from the apex. During hook maintenance ∂[ln(1 + κw)]/∂t is approximately zero if the apex is taken as origin. As each hypocotyl element is displaced from the apex it becomes increasingly curved; then, after displacement past the hook bisector, the element straightens. Growth rates, determined by measurements of the displacement of epidermal hairs, show the pattern expected from the equation: On the apical side of the hook, relative growth rates of the outer edge exceed growth of the inner edge, M(s,o) > M(s,i), while on the basal side of the hook. M(s,o) < M(s,i). The constraint for hook maintenance is that [L(s,o) – L(s,i)] /u(s) be constant in time, where L(s,o) and L(s,i) are the relative elemental growth rates at s. During hook opening ∂[ln(1 + κw)]/∂t becomes important.