Why do cells require heat shock proteins to survive heat stress?

The cellular response to heat stress includes the induction of a group of proteins called the Heat Shock Proteins, whose functions include the synthesis of the thermoprotectant trehalose, refolding of denatured proteins, and ubiquitin- and proteasome-dependent degradation. Recent studies show that simply increasing the activity of ubiquitin- and proteasome-dependent degradation can replace the essential functions played by the induction of heat shock proteins during a heat stress. These results suggest that accumulation of denatured or aggregated proteins is the reason for the loss of cell viability due to heat stress.     

Why do B cells produce CD40 ligand?

The CD40-CD40 ligand (CD40L) interaction is one of the most important receptor-ligand interactions that occurs during a T dependent immune response. However, while CD40L is expressed on a range of cell types including activated T cells and B cells, dendritic cells granulocytes, macrophages and platelets, only CD40L on T cells is considered by most immunologists when planning experiments or analysing data. The current theory professes that T cells expressing CD40L can provide signals to B cells that induce proliferation, immunoglobulin class switching, antibody secretion, rescue from apoptosis at different times during the life of a B cell and also has a role in the development of germinal centres and the survival of memory B cells. However, the whole story is more complex than presently understood as human and mouse B cells express CD40L on their surface following activation and can release a soluble form of the ligand. This paper hypothesizes how CD40L on B cells may regulate antibody responses and the development of germinal centres.     

‘Racism: From the Labour Movement to the Far-Right’

This report is a reflection on a recent conference, ‘Racism: From the Labour Movement to the Far-Right’, which was held at the University of Glasgow from Friday 5th to Saturday 6th September 2014. The authors discuss the main themes that the conference sought to address, consider the key highlights of the event including a summary of the opening address by Floya Anthias, and offer some suggestions as to how the initiative may be taken forward.     

Why do so many petals have conical epidermal cells?

Background

The conical epidermal cells found on the petals of most Angiosperm species are so widespread that they have been used as markers of petal identity, but their function has only been analysed in recent years. This review brings together diverse data on the role of these cells in pollination biology.

Scope

The published effects of conical cells on petal colour, petal reflexing, scent production, petal wettability and pollinator grip on the flower surface are considered. Of these factors, pollinator grip has been shown to be of most significance in the well-studied Antirrhinum majus/bumble-bee system. Published data on the relationship between epidermal cell morphology and floral temperature were limited, so an analysis of the effects of cell shape on floral temperature in Antirrhinum is presented here. Statistically significant warming by conical cells was not detected, although insignificant trends towards faster warming at dawn were found, and it was also found that flat-celled flowers could be warmer on warm days. The warming observed is less significant than that achieved by varying pigment content. However, the possibility that the effect of conical cells on temperature might be biologically significant in certain specific instances such as marginal habitats or weather conditions cannot be ruled out.

Conclusions

Conical epidermal cells can influence a diverse set of petal properties. The fitness benefits they provide to plants are likely to vary with pollinator and habitat, and models are now required to understand how these different factors interact.     

Dendritic cells: making progress with tumour regression?

Due to their potent ability to activate the immune system, dendritic cells (DC) are showing promise as potential adjuvants for tumour immunotherapy of cancer patients. However, little is known about the effect tumour cells can have on DC function. Indeed, the discovery of different DC subsets with different immunological functions indicates that the relationship between tumour cells and tumour-infiltrating DC subtypes is likely to be complex. There remains a lot to be understood about the effects of tumours on DC before we can expect to benefit from DC-based tumour immunotherapy of cancer patients. Here we review the recent advances being made in understanding DC phenotype and function in relation to interactions with different types of tumours.     

Why do cladocerans fail to control algal blooms?

Field studies show that even at high nutrient loads phytoplankton may be kept at low levels by filter-feeding zooplankton for a period of weeks (spring clear water phase in lakes) or months (low-stocked fish-ponds). In the absence of planktivorous fish, large-bodied cladocerans effectively control the abundance of algae of a broad size spectrum. Laboratory experiments show that, although difficult to handle and of poor nutritional value, filamentous algae can also be utilized by large-bodiedDaphnia and prevented from population increase, exactly as the principles of the biomanipulation approach would predict. This is not always the case, however. Even when released from predation, large cladocerans often cannot grow and reproduce fast enough to prevent bloom formation. Sometimes, they disappear when the bloom becomes dense, and the biomanipulation approach is not applicable any more. Recent experimental data on four differently-sizedDaphnia species are used in an attempt to (1) explain why cladocerans fail to control filamentous cyanobacteria when filament density is high, and (2) determine the critical filament density at whichDaphnia becomes ineffective. At this critical concentration,Daphnia growth and reproduction is halted, and no positive numerical response to growing phytoplankton standing crop should be expected fromDaphnia population. Bloom formation thus becomes irreversible. The question of what can be done to overcome this bottleneck of the biomanipulation approach may become one of the most challenging questions in plankton ecology in the nearest future.     

Why are dendritic cells central to cancer immunotherapy?

Dendritic cell (DC)-based immunotherapy is rapidly emerging as a viable alternative to radiation or chemotherapy in the treatment of cancer. The resurgence of interest in cancer immunotherapy reflects the promising results that have been obtained in both animal models and early clinical trials with the DC-based approach. Here I suggest that this optimism is justified because the efficient capture and presentation of antigens by DCs is central to the induction of an immune response. I argue that the mechanism by which DCs capture antigen suggests that the immune system might actually be 'blind' to tumours, thereby challenging the theory of immune surveillance.     

Why do cells need an assembly machine for RNA-protein complexes?

Small nuclear ribonucleoproteins (snRNPs) are crucial for pre-mRNA processing to mRNAs. Each snRNP contains a small nuclear RNA (snRNA) and an extremely stable core of seven Sm proteins. The snRNP biogenesis pathway is complex, involving nuclear export of snRNA, Sm-core assembly in the cytoplasm and re-import of the mature snRNP. Although in vitro Sm cores assemble readily on uridine-rich RNAs, the assembly in cells is carried out by the survival of motor neurons (SMN) complex. The SMN complex stringently scrutinizes RNAs for specific features that define them as snRNAs and identifies the RNA-binding Sm proteins. We discuss how this surveillance capacity of the SMN complex might ensure assembly of Sm cores only on the correct RNAs and prevent illicit, potentially deleterious assembly of Sm cores on random RNAs.     

Why do cancer cells produce serum amyloid a acute-phase protein?

The level of acute-phase serum amyloid A (SAA) protein in human blood dramatically grows in cancer, often at its early stage, when acute inflammatory signs are not observed. This fact was registered both by immunochemistry and by proteomics methods in different common cancers, such as lung, ovarian, renal, uterine, and nasopharyngeal cancer and in melanoma. It was proposed that SAA is produced by liver in such cases, as in inflammation, high levels of SAA being a part of nonspecific response to tumor. However, that was not always true, because, in many cancers, the protein of interest is produced directly by cancer cells. What is the biological significance of this observation? What preferences do cancer cells obtain due to SAA overexpression? Recent data on melanoma patients have shown that serum amyloid A is able to stimulate immunosuppressive neutrophils to produce interleukin-10 cytokine that suppressed cell immunity. The ability of cancer cells to produce SAA that is acquired during cancer mutagenesis is likely to enhance their resistance to T-cell immunity due to activation of immunosuppressive granulocytes.     

From stem cells to red blood cells:how far away from the clinical application?

The generation of red blood cells(RBCs)from stem cells provides a solution for deficiencies in blood transfusion.Currently,primary hematopoietic stem cells,embryonic stem cells and induced pluripotent stem cells have shown the potential to produce fully mature RBCs.Here,we discuss the advantages,induction protocols,progress and possible clinical applications of stem cells in RBC production.     

From co-expression to co-regulation: how many microarray experiments do we need?

Background  

Cluster analysis is often used to infer regulatory modules or biological function by associating unknown genes with other genes that have similar expression patterns and known regulatory elements or functions. However, clustering results may not have any biological relevance.     

From human genes to stem cells: new challenges for patent law?

The social controversies that have surrounded human cloning and the use of embryos for research purposes might create unique patent issues for stem cell researchers. Policy makers should learn from the legal and ethical concerns associated with human gene patents and develop coherent patent policies that recognize and clearly address emerging social controversies.     

From ‘Norwegian citizens’ via ‘citizens plus’ to ‘dual political membership’? Status,aspirations, and challenges ahead

The Norwegian citizenship regime has gradually changed to accommodate some of the demands voiced by or on behalf of the Sami. This article describes and analyses these changes in terms of changing citizenship status for the Sami as a gradual move from ‘Norwegian citizens’ via ‘citizens plus’ to ‘dual citizens’. Sami who are registered in the electoral roster for elections to the Sami Parliament possess political rights connected to two different political systems in Norway: one with membership based on territoriality, the other with membership based on descent. The author argues that the ‘people-to-people’ approach that currently seems to guide Sami aspirations for the political future ignores the condition of dual political membership and is thus ill-suited as a point of departure for discussions of the desirable scope of the future constitutional space of the Sami Parliament in Norway.     

Quantitation of NAD+: Why do we need to measure it?

Background

Nicotinamide adenine dinucleotide (NAD⁺) is an essential pyridine nucleotide that is currently investigated as an important target to extend lifespan and health span. Age-related NAD+ depletion due to the accumulation of oxidative stress is associated with reduced energy production, impaired DNA repair and genomic instability.

Adhesion of cells to protein carpets: do cells' feet have to be black?

In most physiological situations, cell contact with a substratum is mediated by proteins of extracellular matrix. Therefore, an increasing number of cell-substratum adhesion studies employ substrata covered with one or more proteins of extracellular matrix. To visualize the most adhesive cell structures, focal contacts and focal adhesions, the interference reflection microscopy has been widely used. It has been generally accepted that these strongly adhesive structures can be seen as black streaks in interference reflection microscopy. Calculations are presented herein, which although simplified, suggest that when cells are plated on protein-covered substrata, their focal contacts may not always appear black in interference reflection microscopy.     

‘Why do parrots talk?’ co-investigation as a model for promoting family learning through conversation in a natural history gallery*

Research into how and what families learn in science museums and other informal science learning settings suggests that parent-child interactions play an important role in shaping children’s learning experiences. Our exploratory case study set out to discover and analyse learning happening within family groups during a visit to a traditional museum natural history gallery. Research methods were influenced by a growing body of literature that looks for learning in family visitor talk. Conversations of 18 families were recorded as they explored a gallery after being introduced to six learning games which fostered a ‘climate of inquiry’ and which were designed to spark family dialogue. Our findings indicate that families adopt a range of interactional approaches for building meaning together in a museum gallery. These approaches fell along a spectrum that varied according to the level of co-investigation and co-operation between group members. We suggest that family learning could be supported in informal learning contexts through simple, low-cost learning strategies that encourage dialogue and co-investigatory behaviours.     

How do genes make teeth to order through development?

This introduction to new patterning theories for the vertebrate dentition outlines the historical concepts to explain graded sequences in tooth shape in mammals (incisors, canines, premolars, molars) which change in evolution in a linked manner, constant for each region. The classic developmental models for shape regulation, known as the 'regional field' and 'dental clone' models, were inspired by the human dentition, where it is known that the last tooth in each series is the one commonly absent. The mouse, as a valuable experimental model, has provided data to test these models and more recently, based on spatial-temporal gene expression data, the 'dental homeobox code' was proposed to specify regions and regulate tooth shape. We have attempted to combine these hypotheses in a new model of the combinatorial homeobox gene expression pattern with the clone and field theories in one of 'co-operative genetic interaction'. This also explains the genetic absence of teeth in humans ascribed to point mutations in mesenchymally expressed genes, which affect tooth number in each series.