The most common primary malignant tumors of bone after osteosarcoma is chondrosarcoma (1;2). The highest incidence is in the fourth decade of life (2). In addition to bone sarcomas several benign bone neoplasms are known, from some of which little etiology and epidemiological information is available, because many of them are asymptomatic and therefore diagnosed only incidentally. Benign bone t...

Arachidonic acid is a slippery molecule that owes its mobility to its four cis double bonds. These are the source of its flexibility, keeping the pure fatty acid liquid, even at subzero temperatures, and helping to give mammalian cell membranes their correct fluidity at physiological temperatures. The double bonds are also the key to the propensity of arachidonic acid to react with molecular ox...

Although we have demonstrated previously that tissue slices are capable of carrying out a complete synthesis of p-iodophenylmercapturic acid (l), the intermediate compounds and the mechanisms involved in forming the link between the aromatic ring and cysteine sulfur have remained obscure. Various workers have suggested that a primary step is an attachment of the hydrocarbon to the sulfur of a p...

Trypsin-like proteases are synthesized as inactive zymogens and convert to the mature form upon activation by specific enzymes, often assisted by cofactors. Central to this paradigm is that the zymogen does not convert spontaneously to the mature enzyme, which in turn does not feed back to activate its zymogen form. In the blood, the zymogens prothrombin and prethrombin-2 require the prothrombi...

Saliva contacting with solid surfaces in the oral cavity forms a coat termed the pellicle. However, its formation is not fully understood. Although indications for the existence of supramolecular pellicle precursors have been reported, the possible relationship between them and pellicle formation is unclear. This study investigates the ability of supramolecular precursors to form the pellicle v...

Two pathways for biosynthesis of ethylene in higher plants have been postulated (10). One is associated with the breakdown of peroxidized linolenic acid and the other involves the degradation of methionine. Although the formation of ethyilene from peroxidized linolenate has been demonstrated in model systems catalyzed by Cu24, oxygen and ascorbic acid (10) and by an apple extract in the presenc...

Cancer precursors are the tissue antecedents of cancer. They are distinguished from biomarkers in that they reflect a morphologic as opposed to a merely biochemical or genetic association with a specific cancer. Precursors to cancers are increasingly recognized as universal, relevant to carcinogenesis, and providing a unique potential for primary and secondary prevention. As the molecular, imag...

To answer both these questions people have turned to the work of Jean Piaget. And, more recently, they have also considered the writing of Soviet psychologist Lev Vygotsky. Discussion of the relationship between cognition and the child’s emerging use of language generally makes reference to both Piaget and Vygotsky. Piaget’s work was drawn upon in early research on first words (e.g. Bates, 1979...

Sanpodo seals precursors' fate D uring Drosophila development, sensory organ precursor (SOP) cells undergo a series of asym-metric divisions to generate mechanosen-sory bristles along the thorax of adult fl ies. Notch signaling controls the fate of the SOP cells' progeny, ensuring that each bristle contains a single neuron surrounded by hair, socket, and sheath cells. Upadhyay et al. describe h...

It is agreed that infants require pre-existing conceptual meanings to learn language, although little is known about what those meanings are. By default they have been assumed to be the sensorimotor schemas described by Piaget. However, sensorimotor schemas are not concepts and are not the right sort of representation for learning language. Recent research shows that along with sensorimotor sch...