Control of plant growth and development through manipulation of cell-cycle genes

The plant embryo is a relatively simple structure consisting of a primordial shoot and root, whose development is frozen in the form of a seed. Most development of the mature plant takes place post-embryonically, and is the consequence of cell division and organogenesis in small regions known as meristems, which originate in the embryonic shoot and root apices. Significant recent progress has been made in understanding the mechanisms that control the plant cell cycle at a molecular level, and the first attempts have been made to control plant growth through modulation of cell-cycle genes. These results suggest that there is significant potential to control plant growth and architecture through manipulation of cell division rates. However, a full realisation of the promise of such strategies will probably require a much greater understanding of cell division control and how its upstream regulation is co-ordinated by spatial relationships between cells and by environmental signals.     

Triggering the cell cycle in plants

In essence, the mitotic cell cycle in eukaryotes involves the duplication and separation of chromosomes, coupled to the process of dividing one cell into two. Cytokinesis is therefore the culmination of a series of events that were triggered during G1 phase, and brings the daughter cells back to the starting position in G1 for another possible round of division. In all eukaryotes, progression through the cell cycle is controlled by cyclin-dependent kinases that bind to positive regulators called cyclins. This review explores some of the pathways that trigger the plant cell cycle, with emphasis on the G1 phase. Examples include signalling pathways involving glutathione and cellular redox potential, the possible existence of a G1 DNA-damage checkpoint, and the plant hormones auxin and cytokinin. Progress in understanding the link between cell proliferation, cell differentiation and the cell-cycle machinery in a developmental context is discussed.     

Capture and visualization of a catalytic RNA enzyme-product complex using crystal lattice trapping and X-ray holographic reconstruction

We have determined the crystal structure of the enzyme-product complex of the hammerhead ribozyme by using a reinforced crystal lattice to trap the complex prior to dissociation and by employing X-ray holographic image reconstruction, a real-space electron density imaging and refinement procedure. Subsequent to catalysis, the cleavage site residue (C-17), together with its 2',3'-cyclic phosphate, adopts a conformation close to and approximately perpendicular to the Watson-Crick base-pairing faces of two highly conserved purines in the ribozyme's catalytic pocket (G-5 and A-6). We observe several interactions with functional groups on these residues that have been identified as critical for ribozyme activity by biochemical analyses but whose role has defied explanation in terms of previous structural analyses. These interactions may therefore be relevant to the hammerhead ribozyme reaction mechanism.     

Scaling of peak moment arms of elbow muscles with upper extremity bone dimensions.

It is often assumed that moment arms scale with size and can be normalized by body segment lengths or limb circumferences. However, quantitative scaling relationships between moment arms and anthropometric dimensions are generally not available. We hypothesized that peak moment arms of the elbow flexor and extensor muscles scale with the shorter distance (D(s)) between the elbow flexion axis and a muscle's origin and insertion. To test this hypothesis, we estimated moment arms of six muscles that cross the elbow, digitized muscle attachment sites and bone surface geometry, and estimated the location of the elbow flexion axis in 10 upper extremity cadaveric specimens which ranged in size from a 5'0" female to a 6'4" male. D(s) accurately reflected the differences in peak moment arms across different muscles, explaining 93-99% of the variation in peaks between muscles in the same specimen. D(s) also explained between 55% and 88% of the interspecimen variation in peak moment arms for brachioradialis, biceps, and ECRL. Triceps peak moment arm was significantly correlated to the anterior-posterior dimension of the ulna measured at the olecranon (r(2)=0.61, p=0.008). Radius length provides a good measure of the interspecimen variation in peaks for brachioradialis, biceps, and ECRL. However, bone lengths were not significantly correlated to triceps moment arm or anterior-posterior bone dimensions. This work advances our understanding of the variability and scaling dimensions for elbow muscle moment arms across subjects of different sizes.     

The effect of remote chirality on the antibacterial activity of indolinyl, tetrahydroquinolyl and dihydrobenzoxazinyl oxazolidinones

The oxazolidinones are promising agents for the treatment of infections caused by gram-positive bacteria, including multidrug-resistant strains. In ongoing studies we have discovered that a strategically placed chiral center of appropriate absolute configuration improves the antibacterial activity of indolinyl oxazolidinone analogues (gram-positive MIC's<0.5 microg/mL for the most potent congeners). The design, synthesis, antibacterial activity and pharmacokinetic profile of a selected series of alpha-methylated indoline derivatives and a related set of tetrahydroquinolyl and dihydrobenzoxazinyl analogues are discussed.     

Phylogenetic relationships among superfamilies of Hymenoptera

The first comprehensive analysis of higher‐level phylogeny of the order Hymenoptera is presented. The analysis includes representatives of all extant superfamilies, scored for 392 morphological characters, and sequence data for four loci (18S, 28S, COI and EF‐1α). Including three outgroup taxa, 111 terminals were analyzed. Relationships within symphytans (sawflies) and Apocrita are mostly resolved. Well supported relationships include: Xyeloidea is monophyletic, Cephoidea is the sister group of Siricoidea + [Xiphydrioidea + (Orussoidea + Apocrita)]; Anaxyelidae is included in the Siricoidea, and together they are the sister group of Xiphydrioidea + (Orussoidea + Apocrita); Orussoidea is the sister group of Apocrita, Apocrita is monophyletic; Evanioidea is monophyletic; Aculeata is the sister group of Evanioidea; Proctotrupomorpha is monophyletic; Ichneumonoidea is the sister group of Proctotrupomorpha; Platygastroidea is sister group to Cynipoidea, and together they are sister group to the remaining Proctotrupomorpha; Proctotrupoidea s. str. is monophyletic; Mymarommatoidea is the sister group of Chalcidoidea; Mymarommatoidea + Chalcidoidea + Diaprioidea is monophyletic. Weakly supported relationships include: Stephanoidea is the sister group of the remaining Apocrita; Diaprioidea is monophyletic; Ceraphronoidea is the sister group of Megalyroidea, which together form the sister group of [Trigonaloidea (Aculeata + Evanioidea)]. Aside from paraphyly of Vespoidea within Aculeata, all currently recognized superfamilies are supported as monophyletic. The diapriid subfamily Ismarinae is raised to family status, Ismaridae stat. nov. © The Will Henning Society 2011.     

Social, psychological and existential well-being in patients with glioma and their caregivers: a qualitative study

Background:

Cerebral glioma has a devastating impact on cognitive, physical, social, psychological and spiritual well-being. We sought to understand the multidimensional experience of patients with this form of cancer as they progressed from receiving a diagnosis to the terminal phase of the disease.

Methods:

We recruited patients with a suspected brain tumour from a tertiary referral centre in the United Kingdom. We interviewed patients and their caregivers at key stages of the illness: before receiving a formal diagnosis, at the start of initial treatment, after initial treatment was completed and at six months’ follow-up; caregivers were also interviewed postbereavement. We interviewed the patients’ general practitioners once, after treatment had been completed. We transcribed the interviews and analyzed them thematically using the constant comparative method of a grounded theory approach.

Results:

We conducted in-depth interviews with 26 patients, 23 of their relatives and 19 general practitioners. We saw evidence of physical, social, psychological and existential distress even before a diagnosis was confirmed. Social decline followed a similar trajectory to that of physical decline, whereas psychological and existential distress were typically acute around diagnosis and again after initial treatment. Each patient’s individual course varied according to other factors including the availability of support and individual and family resources (e.g., personal resilience and emotional support).

Interpretation:

There are practical ways that clinicians can care for patients with glioma and their caregivers, starting from before a diagnosis is confirmed. Understanding the trajectories of physical, social, psychological and existential well-being for these patients allows health care professionals to predict their patients’ likely needs so they can provide appropriate support and sensitive and effective communication.Cerebral glioma (hereafter glioma) is a rare but devastating cancer.¹ Despite increased treatment options, average survival for the most aggressive form, glioblastoma multiforme, is less than one year.² In addition to physical decline and increasing social isolation,³ patients may undergo a shattering of preconscious assumptions about their life and its meaning,⁴ causing existential anxiety.^5–7 Fear around death and dying are not always verbalized, but may be expressed in other ways, such as concern for relatives or a desire to get one’s affairs in order.⁸ Anxiety related to shock, anger, fear and uncertainty may, with time, be replaced by acceptance.⁸ However, little is known about how these issues interact and vary dynamically as the tumour progresses.We sought to explore qualitatively whether patients with glioma follow archetypal trajectories of physical, social, psychological and existential well-being as their illness progresses. We investigated how people experience and deal with a diagnosis of glioma and the associated transition toward death in an effort to understand the issues patients and caregivers face and the support they need.     

Minimal similarity in songs suggests limited exchange between humpback whales (Megaptera novaeangliae) in the southern Indian Ocean

Comparing humpback whale song from different breeding assemblages can reveal similarities in song due to acoustically interacting males, and therefore indirectly test whether males from different breeding sites are mixing. Northern Hemisphere song comparisons illustrated that whales within ocean basins share similar songs and are subpopulations within a larger population, whereas whales in different ocean basins are isolated populations and therefore do not share songs. During the 2006 breeding season, recordings were collected in Madagascar and Western Australia, and were compared visually plus aurally. Both regions shared one theme, whereas each region had four and six private themes, respectively. This study had a substantially low number of shared themes. The co‐occurrence of one theme was interpreted as an indication of limited exchange between these breeding assemblages, and we speculate that limited song similarity is due to inter‐oceanic interactions. Male(s) from an Indian Ocean breeding group could be exposed to novel song when they geographically overlap, and acoustically interact, with males from a different ocean basin. Novel song could induce rapid temporal changes as new song content is incorporated, thereby minimizing song similarities between that breeding group and other Indian Ocean breeding groups that were not exposed to the novel song.