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.     

Materials for Lithium Batteries Prepared via Mechanochemical Route

1 Results Nanostructured materials are currently of interest for lithium-ion batteries due to relevant demands for high-rate performance batteries and the aspect of structural stability (reversibility) under charge-discharge processes.Decreasing of particle size facilitates the reducing of diffuse paths for lithium ions as compared with micron-sized materials and the increasing of surface contact between electrode and electrolyte leading to acceleration of ionic transport and of charge-discharge process...     

Fluctuating stripes at the onset of the pseudogap in the high-T(c) superconductor Bi(2)Sr(2)CaCu(2)O(8+x)

Doped Mott insulators have a strong propensity to form patterns of holes and spins often referred to as stripes. In copper oxides, doping also gives rise to the pseudogap state, which can be transformed into a high-temperature superconducting state with sufficient doping or by reducing the temperature. A long-standing issue has been the interplay between the pseudogap, which is generic to all hole-doped copper oxide superconductors, and stripes, whose static form occurs in only one family of copper oxides over a narrow range of the phase diagram. Here we report observations of the spatial reorganization of electronic states with the onset of the pseudogap state in the high-temperature superconductor Bi(2)Sr(2)CaCu(2)O(8+x), using spectroscopic mapping with a scanning tunnelling microscope. We find that the onset of the pseudogap phase coincides with the appearance of electronic patterns that have the predicted characteristics of fluctuating stripes. As expected, the stripe patterns are strongest when the hole concentration in the CuO(2) planes is close to 1/8 (per copper atom). Although they demonstrate that the fluctuating stripes emerge with the onset of the pseudogap state and occur over a large part of the phase diagram, our experiments indicate that the stripes are a consequence of pseudogap behaviour rather than its cause.     

Direct expression in Escherichia coli of a DNA sequence coding for human growth hormone.

DNA coding for human growth hormone was constructed by using chemically synthesised DNA in conjunction with enzymatically prepared cDNA. This 'hybrid' gene was expressed in Escherichia coli under the control of the lac promoter. A polypeptide was produced having the size and immunological properties characteristic of mature human growth hormone.     

Insights into phase transition kinetics from colloid science

Colloids display intriguing transitions between gas, liquid, solid and liquid crystalline phases. Such phase transitions are ubiquitous in nature and have been studied for decades. However, the predictions of phase diagrams are not always realized; systems often become undercooled, supersaturated, or trapped in gel-like states. In many cases the end products strongly depend on the starting position in the phase diagram and discrepancies between predictions and actual observations are due to the intricacies of the dynamics of phase transitions. Colloid science aims to understand the underlying mechanisms of these transitions. Important advances have been made, for example, with new imaging techniques that allow direct observation of individual colloidal particles undergoing phase transitions, revealing some of the secrets of the complex pathways involved.     

High-affinity NGF binding requires coexpression of the trk proto-oncogene and the low-affinity NGF receptor.

Nerve growth factor (NGF) interacts with two different low-affinity receptors that can be distinguished by affinity crosslinking. Reconstitution experiments by membrane fusion and transient transfection into heterologous cells indicate that high-affinity NGF binding requires coexpression and binding to both the low-affinity NGF receptor and the tyrosine kinase trk gene product. These studies reveal a new growth factor receptor-mediated mechanism of cellular differentiation involving trk and the low-affinity NGF receptor.     

Transition from haploidy to diploidy

As a direct consequence of sex, organisms undergo a haploid and a diploid stage during their life cycle. Although the relative duration of haploid and diploid phases varies greatly among taxa, the diploid phase is more conspicuous in all higher organisms. Therefore it is widely believed that diploidy offers more evolutionary possibilities and is thus nearly always selected for. We have now performed computer simulations to investigate one possible advantage of diploidy, that is, protection against the expression of deleterious mutations. Instead of comparing isolated haploid and diploid populations, we considered interbreeding haploids and diploids. Diploids invaded the population only when the dominance degree of a single deleterious mutation was smaller than about 1/2, and the condition allowing diploidy to invade depended on how harmful the mutation was.     

Immune sera recognize on erythrocytes Plasmodium falciparum antigen composed of repeated amino acid sequences

Protective immune responses against the asexual stages of the human malaria parasite, Plasmodium falciparum, are most probably directed against exposed antigenic determinants on the surface of the free merozoite or the infected red blood cell, and therefore antigens in these locations are candidates for testing as components of a defined molecular vaccine. To facilitate the search for such antigens, we recently developed a method for the expression of P. falciparum proteins in Escherichia coli as fused polypeptides. Many clones producing antigens were detected by screening with immune human sera. We show here that antibodies against the fused polypeptide expressed by one such clone react with a P. falciparum protein that is synthesized late in schizogony and is later present on the surface of the ring-infected erythrocyte. The protein is composed of repeating subunits of 8, 4 and 3 amino acids and is present in all isolates of P. falciparum examined.     

The complexity of parathyroid hormone-related proteinsignalling

Our understanding of the mode of action of parathyroid hormone-related protein (PTHrP) has changed profoundly during the last decade. Most PTHrP activities are mediated by membrane receptors through autocrine/paracrine pathways. However, both endogenous and exogenous PTHrP also appear to have intracrine effects through translocation into the nucleus. The present review proposes unconventional PTHrP signalling, based on novel clues. First, PTHrP binding to its membrane receptor triggers internalization of the whole complex, mediated by beta-arrestin. There is growing evidence that the receptor and arrestin are the effectors of biological responses, rather than the ligand (or in addition to the ligand). Second, the existence of putative PTHrP targets within the cytoplasm is beginning to be supported. Recent findings of interactions between a COOH-terminus of PTHrP and beta-arrestin and between the PTHrP receptor and 14-3-3 proteins represent the starting point for identification of intracellular partners of both the hormone and its receptor.Received 19 June 2003; received after revision 10 July 2003; accepted 21 July 2003     

The molecular mechanisms of congenital hypofibrinogenaemia

Congenital hypofibrinogenaemia is characterized by abnormally low levels of fibrinogen and is usually caused by heterozygous mutations in the fibrinogen chain genes (, and ). However, it does not usually result in a clinically significant condition unless inherited in a homozygous or compound heterozygous state, where it results in a severe bleeding disorder, afibrinogenaemia. Various protein and expression studies have improved our understanding of how mutations causing hypo- and afibrinogenaemia affect secretion of the mature fibrinogen molecule from the hepatocyte. Some mutations can perturb chain assembly as in the 153 Cys Arg case, while others such as the B Leu Arg and the B414 Gly Ser mutations allow intracellular hexamer assembly but inhibit protein secretion. An interesting group of mutations, such as 284 Gly Arg and 375 Arg Trp, not only cause hypofibrinogenaemia but are also associated with liver disease. The nonexpression of these variant chains in plasma fibrinogen is due to retention in the endoplasmic reticulum, which in turn leads to hypofibrinogenaemia.Received 17 December 2003; received after revision 19 January 2004; accepted 21 January 2004