Genome-wide allelotyping indicates increased loss of heterozygosity on 9p and 14q in early age of onset colorectal cancer.

Colorectal cancer remains a significant public health challenge, despite our increased understanding of the genetic mechanisms involved in the initiation and progression of this disorder. It has become clear that multiple mechanisms lead to the tumorigenic phenotype, with familial predisposition syndromes accounting for less than 15% of all colorectal cancers. A genome-wide scan for loss of heterozygosity (LOH) was carried out with 150 highly polymorphic markers in an effort to identify additional loci involved in colorectal tumorigenesis in DNA samples from 42 colorectal cancer patients. The results confirm earlier observations that tumor DNAs from patients with hereditary nonpolyposis colon cancer (HNPCC) either maintain heterozygosity or exhibit altered or additional alleles. DNAs from patients with early onset colorectal carcinomas (diagnosed prior to age 50) revealed a higher overall degree of LOH than DNAs from patients with sporadic colorectal cancers diagnosed later in life (after age 50). While regions on 1p, 10q and 14q are suggestive, statistical analysis of LOH at these regions failed to reach significance. However, LOH at 9p did reveal a statistically significant increase in the early onset patient group, compared to the greater than age 50 group. LOH on 9p may involve inactivation of p16/CDKN2 through aberrant DNA methylation on the remaining chromosome, resulting in a situation analogous to a homozygous deletion of p16 and providing a selective growth advantage to these cells. This marker may prove to be a useful prognostic indicator for patient stratification in the design of therapy for early onset colorectal cancer patients.     

Association of relatively delayed emergence of mandibular molars with molar reduction and molar position

Among 234 children examined annually from age three to 20 years at the Burlington Growth Centre, there was statistically significant cooccurrence of early and late emergence sequences of the permanent first and second molars relative to the central incisors and second premolars in the same jaw and in both jaws. Alternatively, mandibular molar delay was not accompanied by corresponding maxillary molar delay, and the mandibular molars emerged later than the maxillary molars. This was strongly associated with Angle Class II malocclusion, indicating a relationship between relative time of emergence and relative position of opposing molars. Delay of the mandibular molar relative to the successional teeth or maxillary molars was associated with increased frequency of four cusped first and second molars and agenesis of third molars, indicating a tendency for co-occurrence of delay in timing of molar emergence with reduction in structure of the molars. These relationships were evident even though emergences were affected by early loss of a deciduous second molar which increased M1I1 and M2P2 sequences by earlier emergence of M1 and delayed emergence of P2.     

Light quality during growth of Tradescantia albiflora regulates photosystem stoichiometry, photosynthetic function and susceptibility to photoinhibition

Tradescantia albiflora (Kunth) was grown under two different light quality regimes of comparable light quantity: in red + far-red light absorbed mainly by photosystem I (PSI light) and yellow light absorbed mainly by photosystem II (PSII light). The composition, function and ultrastructure of chloroplasts, and photoinhibition of photosynthesis in the two types of leaves were compared. In contrast to regulation by light quantity (Chow et al. 1991. Physiol. Plant. 81: 175–182), light quality exerted an effect on the composition of pigment complexes, function and structure of chloroplasts in Tradescantia: PSII light-grown leaves had higher Chl a/b ratios, higher PSI concentrations, lower PSII/PSI reaction centre ratios and less extensive thylakoid stacking than PSI light-grown leaves. Light quality triggered modulations of chloroplast components, leading to a variation of photosynthetic characteristics. A larger proportion of primary quinone acceptor (Q_A) in PSI light-grown leaves was chemically reduced at any given irradiance. It was also observed that the quantum yield of PSII photochemistry was lower in PSI light-grown leaves. PSI light-grown leaves were more sensitive to photoinihibition and recovery was slower compared to PSII light-grown leaves, showing that the PSII reaction centre in PSI light-grown leaves was more easily impaired by photoinhibition. The increase in susceptibility of leaves to photoinhibition following blockage of chloroplast-encoded protein synthesis was greater in PSII light-grown leaves, showing that these leaves normally have a greater capacity for PSII repair. Inhibition of zeaxanthin formation by dithiothreitol slightly increased sensitivity to photoinhibition in both PSI and PSII light-grown leaves.     

Infertility in a line of mice with the high growth mutation is due to luteal insufficiency resulting from disruption at the hypothalamic-pituitary axis.

Animals with extreme body growth frequently experience poor reproductive performance, but the cause for this association has not been clearly established. A line of mice homozygous for the high growth (hg) mutation, a mutation that has a major effect on post-weaning growth, exhibits several reproductive deficits including an abnormally high incidence of luteal failure. The objective of the present study was to investigate luteal failure in high-growth (HG) mice during pregnancy and to determine whether the cause of the apparent luteal failure resides in the ovary or the hypothalamic-pituitary unit. In HG females with a demonstrated history of infertility, progesterone injections (1 mg s.c. daily) beginning on Day 1 postcoitum (p.c.) increased the proportion of animals pregnant at Day 17 of gestation. Twice-daily injections of 100 microgram of ovine prolactin (PRL) in alkaline saline given to another group of females beginning on Day 1 p.c. increased the proportion of HG females that were pregnant on Day 6 of gestation compared with saline-injected HG females, although PRL did not increase the pregnancy rate in HG females when compared with a group of noninjected control females. When ovaries from HG females were transplanted into ovariectomized congenic C57 hosts, the C57 graft hosts displayed normal estrous cycles, and upon mating the majority of graft hosts became pregnant. In contrast, when ovaries from C57 females were transplanted into ovariectomized HG hosts, the HG graft hosts displayed normal estrous cycles, but upon mating most were unable to maintain pregnancy. These results suggest that the hypothalamic-pituitary unit of the HG female provides an inadequate signal to the ovaries to maintain pregnancy. Luteal failure in HG females may be due to insufficient PRL as required for establishment and early maintenance of the CL during pregnancy in mice.     

Properties of the transfer functions of compartmental models

This paper is concerned with the nonlinear system of algebraic equations relating the positive parameters of a linear time-invariant compartmental model to its transfer function coefficients. The general form that these equations must take is shown, and simple necessary conditions for the existence of positive solutions are given. An immediate use of these conditions is the development of necessary conditions for a polynomial with positive coefficients to have negative roots. A method is then outlined which triangularizes the system and reduces the complete solution problem to one of finding and counting roots of a polynomial. Sufficient conditions for the existence of real and positive solutions are demonstrated.     

Monoterpenoid indole alkaloids from Palicourea crocea

A new monoterpenoid indole alkaloid N-oxide, 3,4-dihydro-1-(1-β-d-glucopyranosyloxy-1,4a,5,7a-tetrahydro-4-methoxycarbonylcyclopenta[c]pyran-7-yl)-β-carboline-N²-oxide (3) and two known monoterpenoid indole alkaloids, croceaine A (1) and psychollatine (2), were isolated from Palicourea crocea (Rubiaceae) from Trinidad. The structures of 1–3 were determined on the basis of spectral and other physical data. Compounds 1 and 2 were previously isolated from plants of different genera viz. Palicourea crocea and Psychotria umbellata, respectively, both collected in Brazil. The results support the proposal that the genus Palicourea and the subgenus Heteropsychotria should be combined into a single genus.     

ISOLATION OF A NON‐PHAGE‐LIKE LYTIC VIRUS INFECTING AUREOCOCCUS ANOPHAGEFFERENS1

We have been working to characterize viruses that infect the HAB‐forming pelagophyte Aureococcus anophagefferens Hargraves et Sieburth. Field samples were collected during brown‐tide events in 2002 and tested for the presence of lytic agents. Here, we describe a recently isolated, lytic virus‐like particle (VLP) that is morphologically similar to particles observed in thin sections of infected A. anophagefferens cells from natural samples. TEM and SEM have revealed VLPs consistent with the morphological characteristics of previously described Phycodnaviridae. Large icosahedral particles (～140 nm) of similar shape and morphology dominate cell lysates and are accompanied by smaller phage‐like particles and heterotrophic prokaryotes that appear to be incurable from our cultures. To determine which of these particles interacts with the Aureococcus cells, we preserved cultures during the early stage of infection so that SEM could be used to visualize those particles that attach to the surface of naïve cultures. SEM revealed that 63% of the large icosahedral‐shaped particles attached to A. anophagefferens cells after only 30 min of exposure, while no significant frequency of attachment to the alga was observed for the phage‐like particles. The results of these observations are in contrast to previous studies, where phage‐like particles were reported to infect cells. When considered in conjunction with field observations, the results suggest that this newly isolated virus represents the dominant virus‐morphotype associated with bloom collapse and termination.     

Density, dispersal, and feeding impact of western flower thrips (Thysanoptera: Thripidae) on flowering chrysanthemum at different spatial scales

Abstract.  1. This study evaluated the effect of dispersal on the density and feeding impact of a phytophagous insect in relation to the spatial distribution of its host plants.
2. The interaction between density, dispersal, and feeding impact of western flower thrips on flowering chrysanthemum was quantified at three spatial scales, with infested and uninfested plants either isolated in 0.25 m² individual cages, or enclosed together in 2.25 m² communal cages or 75 m² greenhouses.
3. In individual cages, the rate of dispersal from chrysanthemum plants to blue sticky traps increased with the density of thrips for females but not males. Uninfested plants consistently had fewer thrips when they were individually caged rather than enclosed with plants infested with adults, indicating that dispersal mediates inter-plant distribution of thrips.
4. The feeding impact of thrips on inflorescences was evaluated using the absorbance of ethanol extracts at wavelengths characteristic of yellow carotenoid pigments associated with chrysanthemum inflorescences (415, 445, and 472 nm). Increasing absorbance of extracts with increasing density of thrips per inflorescence suggests that feeding by thrips results in ruptured cells leaching carotenoid pigments.
5. In communal cages, the distribution of thrips was uniform for infested and uninfested plants, whereas the density and feeding impact of thrips in greenhouses were higher for infested than uninfested plants. These results suggest that short-range dispersal by adults homogenises the density and feeding impact of thrips among host plants only on a small spatial scale.     

A Versatile Click-Compatible Monolignol Probe to Study Lignin Deposition in Plant Cell Walls

Lignin plays important structural and functional roles in plants by forming a hydrophobic matrix in secondary cell walls that enhances mechanical strength and resists microbial decay. While the importance of the lignin matrix is well documented and the biosynthetic pathways for monolignols are known, the process by which lignin precursors or monolignols are transported and polymerized to form this matrix remains a subject of considerable debate. In this study, we have synthesized and tested an analog of coniferyl alcohol that has been modified to contain an ethynyl group at the C-3 position. This modification enables fluorescent tagging and imaging of this molecule after its incorporation into plant tissue by click chemistry-assisted covalent labeling with a fluorescent azide dye, and confers a distinct Raman signature that could be used for Raman imaging. We found that this monolignol analog is incorporated into in vitro-polymerized dehydrogenation polymer (DHP) lignin and into root epidermal cell walls of 4-day-old Arabidopsis seedlings. Incorporation of the analog in stem sections of 6-week-old Arabidopsis thaliana plants and labeling with an Alexa-594 azide dye revealed the precise locations of new lignin polymerization. Results from this study indicate that this molecule can provide high-resolution localization of lignification during plant cell wall maturation and lignin matrix assembly.