Keith L. Manchester

Theodor Boveri and the origin of malignant tumours

As long ago as 1914, Theodor Boveri suggested that there is an inhibitory mechanism in every normal cell that prevents the process of cell division until the inhibition has been overcome by a special stimulus. From his work on abnormal mitoses in the eggs of echinoderms, Boveri also suggested that the inhibitor resided in the chromosomes. The relevance of Boveris ideas to modern cancer research is discussed in this Retrospective article.

Histochemical and biochemical characteristics of the transient hypertrophy of the denervated rat hemidiaphragm

A systematic study of the different fiber types of rat diaphragm muscle in the first 10 days after unilateral denervation showed approximately a 10% decrease in diameter of the white fibers, 25% increase in that of intermediate fibers, and 35% increase in that of red fibers together with diminished differential staining properties both for myosin ATPase and Sudan black. There was also a doubling of the amount of connective tissue. A reduction in total lipid concentration of the tissue included decreases in both triacylglycerol and phospholipid, but not cholesterol. Magnesium concentration in the tissue also declined, as did activity of Ca2+-activated, though not Mg2+-activated, myosin ATPase.

The intracellular ionic strength of red cells and the influence of complex formation

Various cellular features of red blood cells, such as transmembrane transport and the physicochemical properties of haemoglobin, are affected by ionic strength. In relation to sickle cell and other abnormal forms of haemoglobin, the effects of ionic strength assume biomedical relevance. The knowledge of the actual value of intracellular ionic strength is therefore important when performing in vitro studies. A comparison is made here of the intracellular ionic strength of red cells, depending on whether complex formation between multivalent ions is taken into account. A 20% difference is found, which for cell-free experiments would have significant consequences for a number of red cell-related processes. Complex formation between ions should therefore be considered in assuming a value of intracellular ionic strength.

The quest by three giants of science for an understanding of cancer

Understanding the causes of cancer remains a major area of uncertainty, and many serious proposals have been made from a variety of standpoints over the years. This article discusses the first genetic hypothesis from the turn of the century and two other totally different early approaches to the problem.

Louis Pasteur (1822-1895)--chance and the prepared mind.

Louis Pasteur is often regarded as one of the founders of microbiology, and is chiefly famous for his discovery of the role that microorganisms play in health and disease. However, he was trained as a physical scientist, and his research began with the discovery of the stereoisomerism of the different forms of tartaric acid. As a biotechnologist, he is remembered for his studies on the nature of fermentation, and for his rebuttal of the theory of spontaneous generation.

Determination of magnesium and potassium binding constants to phosphoenolpyruvate, 2- and 3-phosphoglycerate and a number of other anions

The stability constants for the binding of magnesium ions to phosphoenolpyruvate, 2- and 3-phosphoglycerates, 2,3-diphosphoglycerate, Pi, glucose 6-phosphate, isocitrate, glutamate and NAD have been determined spectrophotometrically in the presence of 8-hydroxyquinoline at 25 and 37 degrees C. Estimates of potassium binding constants have also been calculated for phosphoenolpyruvate and 2- and 3-phosphoglycerate and compared with previously published values.

Control of activity of S-adenosylmethionine decarboxylase in muscle by spermidine

Synthesis of the polyamines spermidine and spermine from the amino acids ornithine and methionine involves two decarboxylases, ornithine decarboxylase (EC 4.1.1.17), converting ornithine to putrescine, and S-adenosylmethionine decarboxylase (EC 4.1 .I SO), converting S-adenosylmethionine to its decarboxylated form, from which the propylamine unit is transferred to putrescine to form spermidine. The two decarboxylases are often considered to be the ratelimiting enzymes in polyamine synthesis [ 1,2]. Ornithine decarboxylase is believed to possess a very short half-life and its activity is affected by a variety of stimuli, usually of a growth-promoting nature [3,4]. However its activity has frequently been observed to show a biphasic response, rising rapidly and equally rapidly falling [ 15-71. Administration of exogenous putrescine appears to bring about a sharp decrease in extractable activity [6,8,9], and it is possible that a rapid elevation in putrescine concentration in vivo, as a result of enhanced ornithine decarboxylase activity, may in turn lead to suppression of further enzyme synthesis. Administration of spermidine also diminishes the rise in hepatic ornithine decarboxylase activity following partial hepatectomy [61. Control of adenosylmethionine decarboxylase activity has been less studied. Incubation of lymphocytes with putrescine or spermidine was found to lower activity of both ornithine decarboxylase and adenosylmethionine decarboxylase [lo], whereas injection of spermidine in the hen was found to produce a dramatic increase in hepatic adenosylmethionine decarboxylase

Evaluation and significance of kinetic parameters governing function of protein synthesis initiation factors eIF-2 and eIF-2B

Initiation factor eIF‐2 Initiation factor eIF‐2B Ternary complex

Control of cell-free protein synthesis by amino acids: Effects on tRNA charging

In order to resolve the observation that addition of glutamine and glutamate appears to be of particular importance in enhancing the activity of a cell-free protein synthesis system derived from rat liver (Manchester and Tyobeka, 1980), we have measured the KM of the aminoacyl-tRNA synthetases towards amino acids and the extent of aminoacylation of tRNA under the conditions of our earlier experiments. During incubation of the cell-free system in the presence of an amino acid mixture the extent of acylation to tRNA of 15 amino acids studied showed no clear change from initial time values. When incubation took place in the absence of added amino acids, however, the levels of glutamate and glutamine bound to their appropriate tRNAs dropped more rapidly and to lower levels than for other amino acids except tryptophan. The pronounced drop for these two amino acids does not seem to result from an abnormally high KM value for the synthetases towards the respective amino acids, nor an abnormally low Vmax, but probably from the fact that the amounts of glutamyl and glutaminyl-tRNA in the cell-free system are comparatively low.

Influence of serum and insulin of the accumulation of aminoisobutylrate by rat hepatoma cells

1. Cultured rat hepatoma cells accumulate 2-aminoisobutyrate to high concentrations by a transport mechanism probably of the A type mediation. 2. Transport is enhanced by the presence of serum. When cells are deprived of serum the rate of transport declines over a period of hours; conversely addition of serum leads over a period of hours to increase in transport activity. In the presence of serum the apparent Km for aminoisobutyrate uptake is about 8 mM. In cells deprived of serum the Km is much higher. 3. Addition of insulin produces both an immediate increase in the rate of aminoisobutyrate uptake and a time-dependent rise. 4. The presence of alanine diminished aminoisobutyrate uptake in a concentration-dependent fashion. Competition is seen both in the presence and absence of serum but not when cells are incubated at 4 degrees C. 5. Preincubation with alanine for 1 h also diminishes aminoisobutyrate uptake when the alanine is removed. Cells take a period of several hours to recover from the depression of transport induced by alanine. 6. Transport of aminoisobutyrate rapidly declines in the presence of cycloheximide. Actinomycin had no effect for at least 8 h.