Plating efficiency of mouse embryo cells as a function of gestational age

Summary Mouse embryo cells can be plated directly from single-cell suspensions of fresh embryos. For randomly bred Swiss mice, there is an increase in plating efficiency as a function of gestational age. Colony-forming units appear at about day 10 and there is an exponential increase in colony-forming ability up to day 16, after which there is no further increase.The technical assistance of Ms.Helen Sandza is gratefully acknowledged. This work was supported by a grant from the National Cancer Institute (No. CA13053).     

Mechanical properties of the radula protractor ofBusycon canaliculatum

Zusammenfassung Der Radula Protractormuskel vonBusycon canaliculatum unterscheidet sich vom Herzmuskel, aber er verhält sich wie andere glatte Muskeln von andern Mollusken in der Beziehung zwischen passiver und aktiver Kraft.     

Evolutionary relationships of human populations from an analysis of nuclear DNA polymorphisms

The genetic relationships of human populations have been studied by comparing gene frequency data for protein and blood-group loci of different populations. DNA analysis now promises to be more informative since not only do the DNA coding sequences have more variation than their corresponding proteins but, in addition, noncoding DNA sequences display more extensive polymorphism. We have now studied the frequency of a group of closely linked nuclear DNA polymorphisms (haplotypes) in the beta-globin gene cluster of normal (beta A) chromosomes of individuals from eight diverse populations. We have found that all non-African populations share a limited number of common haplotypes whereas Africans have predominantly a different haplotype not found in other populations. Genetic distance analysis based on these nuclear DNA polymorphisms indicates a major division of human populations into an African and a Eurasian group.     

Vaccines against intracellular infections requiring cellular immunity

Vaccines against a variety of infectious diseases represent one of the great triumphs of medicine. The immune correlates of protection induced by most current vaccines seem to be mediated by long-lived humoral immune responses. By contrast, there are no currently available vaccines that are uniformly effective for diseases such as HIV, malaria and tuberculosis, in which the cellular immune response might be crucial in mediating protection. Here we examine the mechanisms by which long-lived cellular immune responses are generated and maintained in vivo. We then discuss current approaches for vaccination against diseases in which cellular immune responses are important for protection.     

Image reconstructions of helical assemblies of the HIV-1 CA protein

The type 1 human immunodeficiency virus (HIV-1) contains a conical capsid comprising approximately 1,500 CA protein subunits, which organizes the viral RNA genome for uncoating and replication in a new host cell. In vitro, CA spontaneously assembles into helical tubes and cones that resemble authentic viral capsids. Here we describe electron cryo-microscopy and image reconstructions of CA tubes from six different helical families. In spite of their polymorphism, all tubes are composed of hexameric rings of CA arranged with approximate local p6 lattice symmetry. Crystal structures of the two CA domains were 'docked' into the reconstructed density, which showed that the amino-terminal domains form the hexameric rings and the carboxy-terminal dimerization domains connect each ring to six neighbours. We propose a molecular model for the HIV-1 capsid that follows the principles of a fullerene cone, in which the body of the cone is composed of curved hexagonal arrays of CA rings and the ends are closed by inclusion of 12 pentagonal 'defects'.     

Warm-coding deficits and aberrant inflammatory pain in mice lacking P2X3 receptors

ATP activates damage-sensing neurons (nociceptors) and can evoke a sensation of pain. The ATP receptor P2X3 is selectively expressed by nociceptors and is one of seven ATP-gated, cation-selective ion channels. Here we demonstrate that ablation of the P2X3 gene results in the loss of rapidly desensitizing ATP-gated cation currents in dorsal root ganglion neurons, and that the responses of nodose ganglion neurons to ATP show altered kinetics and pharmacology resulting from the loss of expression of P2X(2/3) heteromultimers. Null mutants have normal sensorimotor function. Behavioural responses to noxious mechanical and thermal stimuli are also normal, although formalin-induced pain behaviour is reduced. In contrast, deletion of the P2X3 receptor causes enhanced thermal hyperalgesia in chronic inflammation. Notably, although dorsal-horn neuronal responses to mechanical and noxious heat application are normal, P2X3-null mice are unable to code the intensity of non-noxious 'warming' stimuli.