Integrin adhesion: when is a kinase a kinase?

Recent genetic studies in the worm Caenorhabditis elegans and fruitfly Drosophila have revealed the essential role integrin-linked kinase plays in integrin adhesion - but it apparently acts in this role as an adaptor rather than a kinase.     

Beta-carotene: a cancer chemopreventive agent or a co-carcinogen?

Evidence from both epidemiological and experimental observations have fueled the belief that the high consumption of fruits and vegetables rich in carotenoids may help prevent cancer and heart disease in humans. Because of its well-documented antioxidant and antigenotoxic properties, the carotenoid beta-carotene (betaCT) gained most of the attention in the early 1980s and became one of the most extensively studied cancer chemopreventive agents in population-based trials supported by the National Cancer Institute. However, the results of three randomized lung cancer chemoprevention trials on betaCT supplementation unexpectedly contradicted the large body of epidemiological evidence relating to the potential benefits of dietary carotenoids. Not only did betaCT show no benefit, it was associated with significant increases in lung cancer incidence, cardiovascular diseases, and total mortality. These findings aroused widespread scientific debate that is still ongoing. It also raised the suspicion that betaCT may even possess co-carcinogenic properties. In this review, we summarize the current data on the co-carcinogenic properties of betaCT that is attributed to its role in the induction of carcinogen metabolizing enzymes and the over-generation of oxidative stress. The data presented provide convincing evidence of the harmful properties of this compound if given alone to smokers, or to individuals exposed to environmental carcinogens, as a micronutrient supplement. This has now been directly verified in a medium-term cancer transformation bioassay. In the context of public health policies, while the benefits of a diet rich in a variety of fruits and vegetables should continue to be emphasized, the data presented here point to the need for consideration of the possible detrimental effects of certain isolated dietary supplements, before mass cancer chemoprevention clinical trials are conducted on human subjects. This is especially important for genetically predisposed individuals who are environmentally or occupationally exposed to mutagens and carcinogens, such as those found in tobacco smoke and in industrial settings.     

Intra-Golgi transport: a way to a new paradigm?

The morpho-functional principles of intra-Golgi transport are, surprisingly, still not clear, which is in marked contrast to our advanced knowledge of the underlying molecular machineries. Recently, the conceptual and technological hindrances that had delayed progress in this area have been disappearing, and a cluster of powerful morphological techniques has been revealing new glimpses of the organization of traffic in intact cells. Here, we discuss the new concepts around the present models of intra-Golgi transport.     

“Doing a Lynndie”: Iconography of a Gesture

In the fall of 2003, Lynndie England gave thumbs-up with one hand and lock-and-load with the other to a group of naked Iraqi detainees at Abu Ghraib prison, when facing a camera. Soon after the Abu Ghraib tortures became public knowledge, and Lynndie England became an iconic “Hillbilly” who tortures for fun, hundreds of people around the world, prompted by a British blog named Bad Gas, took up Lynndie's gesture and transformed it into a humorous everyday practice. This article attempts to illuminate the processes that transform iconic images into embodied commonsense cultural practices by tracing the life of Lynndie's gesture across a varied and complex media landscape. It poses questions about the role that popular media played in providing mainstream discursive frameworks about the Abu Ghraib tortures and about the role of social media in transforming these discourses into humorous practices.     

Centrosome competition: a possibility?

A recent theory on the evolution of sexuality, has hypothesized heritable variation in the functional properties of centrosomes, leading to competition for the organization of the mitotic spindle when different centrosomes enter a common cytoplasm. We present here data on polyethylene glycol-induced polykaryocytes of cultured Chinese hamster fibroblasts indirectly supporting centrosome competition. On the assumption that sib centrosomes are similar and variation increases with cell generations, the frequencies of multipolar mitoses were compared in cultures fused under conditions favoring sib cell fusion or fusion of distantly related cells. Multipolar mitoses were considerably more frequent in the former, when the average difference between pairs of centrosomes was assumed to be too small for one centrosome to "outcompete" the other.     

Superparasitism: a non-adaptive strategy?

Although once thought to be detrimental, superparasitism (where a host is parasitized more than once) by solitary parasitoids is now accepted to be an adaptive strategy. However, a recent study reveals that this might not always be the case. Varaldi et al. show that the superparasitism behaviour of the wasp Leptopilina boulardi is caused by a vertically and horizontally transmitted infectious agent. A reinterpretation of the adaptive significance of superparasitism in this species might therefore be required.     

Speech rhythm: a metaphor?

Is speech rhythmic? In the absence of evidence for a traditional view that languages strive to coordinate either syllables or stress-feet with regular time intervals, we consider the alternative that languages exhibit contrastive rhythm subsisting merely in the alternation of stronger and weaker elements. This is initially plausible, particularly for languages with a steep ‘prominence gradient’, i.e. a large disparity between stronger and weaker elements; but we point out that alternation is poorly achieved even by a ‘stress-timed’ language such as English, and, historically, languages have conspicuously failed to adopt simple phonological remedies that would ensure alternation. Languages seem more concerned to allow ‘syntagmatic contrast’ between successive units and to use durational effects to support linguistic functions than to facilitate rhythm. Furthermore, some languages (e.g. Tamil, Korean) lack the lexical prominence which would most straightforwardly underpin prominence of alternation. We conclude that speech is not incontestibly rhythmic, and may even be antirhythmic. However, its linguistic structure and patterning allow the metaphorical extension of rhythm in varying degrees and in different ways depending on the language, and it is this analogical process which allows speech to be matched to external rhythms.     

Genetics: still a discipline?

In the institutional sense of the term "discipline" (laboratories, societies, congresses, curricula, etc.), genetics remains a discipline. In the intellectual sense of the term (consensus on a definite array of concepts, methods and theoretical purposes), it is doubtful that genetics is still a discipline. At first, molecular biology seemed to have introduced an unequivocal structural (or molecular) definition of the gene: a definite sequence of nucleotides that code for a protein. In fact, as it appears in retrospect, this was not the case. Even in 1961, when Jacob and Monod proposed their first model of genetic regulation in bacteria, there was no possibility of constructing a non equivocal concept of the gene. More recent developments in molecular genetics have made this situation worse. There is no possible definition of the gene as a general category. The reasons why biologists keep the word are pragmatic rather than theoretical: communication among scientists, economic interests and ideology.     

Heterochromatin: a meiotic matchmaker?

During meiosis, the pairing of chromosomes is crucial for a successful partitioning of the genetic material and its transmission into the developing gamete. The classical view of meiotic pairing involves recombination between homologues as an integral part of the pairing mechanism. But, in cases where no recombination occurs, how do chromosome partners find one another? And how do they pair up and then segregate appropriately? Recently, a combination of molecular genetics and fluorescence in situ hybridization appears to have provided an answer to these questions by demonstrating a crucial role for heterochromatin in chromosome pairing.     

Gestational diabetes: a non-entity?

Screening for gestational diabetes is commonly recommended despite the absence of a common definition of gestational diabetes. Furthermore, there is no consensus about management or treatment. Those who recommend screening do so largely on the basis of fetal morbidity, which seems to be predominantly "macrosomia"--another term without an agreed definition. The implications of macrosomia in terms of actual morbidity are also not clear. R J Jarrett reviews the history of the subject and concludes that gestational diabetes is simply impaired glucose tolerance temporally associated with pregnancy. Its main importance is as a predictor of subsequent non-insulin dependent diabetes, but it fails the major tests for a condition suitable for a screening programme.     

Fibronectin: a chromatin-associated protein?

We have previously reported that chromatin preparations from human cultured fibroblasts contain a single homologous serum protein. In this paper we present evidence, based on immunological identity and physicochemical properties, that this serum protein is fibronectin. Furthermore, using a radioimmunoassay system, we have estimated that fibronectin represents about 0.7% of the total protein in both chromatin preparations and whole fibroblasts. Using a nitrocellulose filter assay system, we also show that fibronectin is a DNA-binding protein having an equilibrium constant of 4.6 x 10(-6) M. Equilibrium competition experiments have demonstrated that fibronectin has the ability to differentiate among nucleotides, indicating that fibronectin-DNA interaction is at least partially specific, and that a minimum polymer length of 12-18 nucleotides is required for effective binding to occur. Fibronectin has been isolated readily from plasma using DNA-affinity chromatography. We do not have direct evidence that fibronectin is an actual nonhistone chromosomal protein, but fibronectin is a DNA-binding protein (at least under in vitro assay conditions) and appears to be a normal constituent of chromatin as chromatin is currently isolated from cell nuclei.     

Haematemesis: a new syndrome?

Three patients presented with symptoms suggesting a Mallory-Weiss tear. Endoscopy showed a localized, clearly demarcated area of bright red mucosa near the gastro-oesophageal junction; this was thought to have arisen by retrograde intussusception of the stomach during vomiting or retching and may have caused the haemorrhage.     

Huntington's disease: a synaptopathy?

Huntington's disease (HD) is caused by a polyglutamine expansion in the protein huntingtin. In its terminal stage, HD is characterized by widespread neuronal death in the neocortex and the striatum. Classically, this neuronal death has been thought to underlie most of the symptoms of the disease. Accumulating evidence suggests, however, that cellular dysfunction is important in the pathogenesis of HD. We propose that specific impairment of the exocytosis and endocytosis machinery contributes to the development of HD. We also suggest that abnormal synaptic transmission underlies the early symptoms of HD and can contribute to the triggering of cell death in later stages of the disease.