Insulin-stimulated MAP-2 kinase phosphorylates and activates ribosomal protein S6 kinase II

Ribosomal protein S6 is a component of the eukaryotic 40S ribosomal subunit that becomes phosphorylated on multiple serine residues in response to a variety of mitogens, including insulin, growth factors, and transforming proteins of many oncogenic viruses. Recently, an activated S6 kinase (S6 K II) has been purified to homogeneity from Xenopus eggs, and characterized immunologically and at the molecular level. Purified S6 K II can be deactivated in vitro by incubation with either protein phosphatase 1 or protein phosphatase 2A. Reactivation and phosphorylation of S6 K II occurs in vitro with an insulin-stimulated microtubule-associated protein-2 (MAP-2) protein kinase which is itself a phosphoprotein that can be deactivated by protein phosphatase 2A. These studies suggest that a step in insulin signalling involves sequential activation by phosphorylation of at least two serine/threonine protein kinases.     

Protease inhibitor domain encoded by an amyloid protein precursor mRNA associated with Alzheimer's disease

Amyloid B-protein/amyloid A4 is a peptide present in the neuritic plaques, neurofibrillary tangles and cerebrovascular deposits in patients with Alzheimer's disease and Down's syndrome (trisomy 21) and may be involved in the pathogenesis of Alzheimer's disease. Recent molecular genetic studies have indicated that amyloid protein is encoded as part of a larger protein by a gene on human chromosome 21 (refs 6-9). The amyloid protein precursor (APP) gene is expressed in brain and in several peripheral tissues, but the specific biochemical events leading to deposition of amyloid are not known. We have now screened complementary DNA libraries constructed from peripheral tissues to determine whether the messenger RNA encoding APP in these tissues is identical to that expressed in brain, and we identify a second APP mRNA that encodes an additional internal domain with a sequence characteristic of a Kunitz-type serine protease inhibitor. The alternative APP mRNA is present in both brain and peripheral tissues of normal individuals and those with Alzheimer's disease, but its pattern of expression differs from that of the previously reported APP mRNA.     

Resolution of quantitative traits into Mendelian factors by using a complete linkage map of restriction fragment length polymorphisms

The conflict between the Mendelian theory of particulate inheritance and the observation of continuous variation for most traits in nature was resolved in the early 1900s by the concept that quantitative traits can result from segregation of multiple genes, modified by environmental effects. Although pioneering experiments showed that linkage could occasionally be detected to such quantitative trait loci (QTLs), accurate and systematic mapping of QTLs has not been possible because the inheritance of an entire genome could not be studied with genetic markers. The use of restriction fragment length polymorphisms (RFLPs) has made such investigations possible, at least in principle. Here, we report the first use of a complete RFLP linkage map to resolve quantitative traits into discrete Mendelian factors, in an interspecific back-cross of tomato. Applying new analytical methods, we mapped at least six QTLs controlling fruit mass, four QTLs for the concentration of soluble solids and five QTLs for fruit pH. This approach is broadly applicable to the genetic dissection of quantitative inheritance of physiological, morphological and behavioural traits in any higher plant or animal.     

Novel anti-inflammatory peptides from the region of highest similarity between uteroglobin and lipocortin I

Significant future developments in the effective treatment of inflammatory diseases may arise from non-toxic dual inhibitors of both cyclooxygenase and lipoxygenase pathways in the arachidonate cascade. Inhibition of phospholipase A2(PLA2)(EC3.1.1.4), may provide such a dual action and recent research has concentrated on the role of PLA2-inhibitory proteins as possible anti-inflammatory agents. Blastokinin or uteroglobin is a steroid-induced rabbit secretory protein with PLA2-inhibitory activity. Its biochemical and biological properties have been extensively studied and its crystallographic structure has been resolved at 1.34 A (refs 15, 16). Lipocortins are a family of related proteins, which, it has been suggested, mediate the anti-inflammatory effects of glucocorticoids (for a review, see ref. 23). Some proteins of this group have been purified and the complementary DNA sequences of two human lipocortins are known. Lipocortins inhibit PLA2 in vitro, although their mechanism of action is still unclear. Recombinant lipocortin I inhibits eicosanoid synthesis in isolated perfused lungs from the guinea pig. Here, we report that synthetic oligopeptides corresponding to a region of high amino-acid sequence similarity between uteroglobin and lipocortin I have potent PLA2 inhibitory activity in vitro and striking anti-inflammatory effects in vivo.     

Inositol 1,4,5-trisphosphate activates a channel from smooth muscle sarcoplasmic reticulum

Inositol 1,4,5-trisphosphate (InsP3) can initiate calcium release into the cytoplasm in a variety of cells. From experiments using permeabilized cells, membrane vesicles, and patch-clamp techniques, it has been suggested that InsP3 acts by directly opening calcium channels. Here, we show that InsP3 induced openings of channels in planar lipid bilayers into which vesicles made from aortic muscle sarcoplasmic reticulum (SR) were incorporated. Activation of channels by InsP3 was not observed when vesicles made from SR of cardiac or skeletal muscle were incorporated into planar lipid bilayers. The present study demonstrates for the first time unique properties of an InsP3-gated calcium channel in sarcoplasmic reticulum vesicles from vascular smooth muscle. This InsP3-activated channel from aortic SR differs strikingly from the calcium-gated calcium channel of striated muscle SR in single-channel conductance and pharmacology.     

Multiple liquid crystal phases of DNA at high concentrations

DNA packaging in vivo is very tight, with volume concentrations approaching 70% w/v in sperm heads, virus capsids and bacterial nucleoids. The packaging mechanisms adopted may be related to the natural tendency of semi-rigid polymers to form liquid crystalline phases in concentrated solutions. We find that DNA forms at least three distinct liquid crystalline phases at concentrations comparable to those in vivo, with phase transitions occurring over relatively narrow ranges of DNA concentration. A weakly birefringent, dynamic, 'precholesteric' mesophase with microscopic textures intermediate between those of a nematic and a true cholesteric phase forms at the lowest concentrations required for phase separation. At slightly higher DNA concentrations, a second mesophase forms which is a strongly birefringent, well-ordered cholesteric phase with a concentration-dependent pitch varying from 2 to 10 micron. At the highest DNA concentrations, a phase forms which is two-dimensionally ordered and resembles smectic phases of thermotropic liquid crystals observed with small molecules.     

Incubation periods for paediatric AIDS patients

A recent seroprevalence study of newborns indicates that one in 62 children born in New York City has antibodies to the human immunodeficiency virus (HIV). The distribution of incubation periods for paediatric patients is needed to estimate future AIDS case loads from these seroprevalence data. Current estimates of incubation periods for paediatric patients are based on limited data. We use parametric and non-parametric methods to analyse incubation periods for 215 paediatric patients with AIDS whose only known route of infection is maternal. We conclude that incubation periods are longer than previously reported; that there is a distinct knee in the incubation period distribution at seven months which suggests two risk populations; and that there is an increase in incidence which is consistent with exponential growth.     

Neural encoding of individual words and faces by the human hippocampus and amygdala

Patients with lesions in the medial temporal lobe (MTL) of the brain, which includes the hippocampus, amygdala and parahippocampal gyrus, are severely impaired in their ability to remember and recognize words or faces which they saw only a short time ago. These lesions also prevent the effect of word repetition on cortical event-related potentials that are associated with these tasks. We have been able to study the response of individual neurons in the human medial temporal lobe to such delayed recognition tasks in epileptic patients undergoing neurosurgery. We found that some MTL neurons preferentially fired on sight of one particular word from a set of ten words used in a memory task, and others fired in response to one particular face. This stimulus-specific firing was maximal during the time that the neocortical event potentials are most sensitive to stimulus repetition, suggesting that the MTL contributes specific information to the cortex during the retrieval of recent memories.     

Expression of human proteoglycan in Chinese hamster ovary cells inhibits cell proliferation

In studying the functional role of an extracellular matrix proteoglycan, decorin, we have made observations that suggest a role for this proteoglycan in the control of cell proliferation. Extracellular matrices are made up of different combinations of collagens, elastin, hyaluronic acid, proteoglycans and various glycoproteins such as fibronectin. Most of these components can interact with cells, and much of the control of cell adhesion, migration and differentiation appears to be mediated by these interactions. Earlier studies have also attributed growth-regulatory activities to intact extracellular matrices, but the individual molecules responsible for these effects have not been characterized. We report here that Chinese hamster ovary (CHO) cell lines expressing human decorin from a stably transfected complementary DNA construct form a more orderly monolayer and grow to a lower saturation density than control cells lacking decorin. The extent of the morphological changes correlates with the level of decorin expression, and the saturation density is inversely proportional to it. The reduction in the saturation densities of the cell lines with the highest expression of decorin is more than 50%. These results reveal a novel growth inhibitory mechanism which may be related to contact inhibition of cell proliferation.     

Pattern of covariation between life-history traits of European birds

A large amount of variation is found in most reproductive traits of birds. Clutch size for instance, can vary from 1 to 15 between species of similar body weight. The adaptive significance of this variation is only poorly understood. According to life-history theory, large clutch size and early onset of reproduction are expected when the chances of survival are low. There is some support for the existence of such a relationship from studies of single species. Here I present evidence that, in European birds, clutch size is increased, and onset of reproduction occurs earlier in life, when the probability of survival is low.