James C. Smith

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The Brachyury (T) gene is required for mesoderm formation in the mouse. In this paper we describe the cloning and expression of a Xenopus homolog of Brachyury, Xbra. As with Brachyury in the mouse, Xbra is expressed in presumptive mesodermal cells around the blastopore, and then in the notochord. We show that expression of Xbra occurs as a result of(More)
The location of neurons generating the rhythm of breathing in mammals is unknown. By microsection of the neonatal rat brainstem in vitro, a limited region of the ventral medulla (the pre-Bötzinger Complex) that contains neurons essential for rhythmogenesis was identified. Rhythm generation was eliminated by removal of only this region. Medullary slices(More)
New protein parameters are reported for the all-atom empirical energy function in the CHARMM program. The parameter evaluation was based on a self-consistent approach designed to achieve a balance between the internal (bonding) and interaction (nonbonding) terms of the force field and among the solvent-solvent, solvent-solute, and solute-solute(More)
Gastrulation in the amphibian embryo is driven by cells of the mesoderm. One of the genes that confers mesodermal identity in Xenopus is Brachyury (Xbra), which is required for normal gastrulation movements and ultimately for posterior mesoderm and notochord differentiation in the development of all vertebrates. Xbra is a transcription activator, and(More)
Vertebrate gastrulation involves the specification and coordinated movement of large populations of cells that give rise to the ectodermal, mesodermal and endodermal germ layers. Although many of the genes involved in the specification of cell identity during this process have been identified, little is known of the genes that coordinate cell movement. Here(More)
A network of oscillatory bursting neurons with excitatory coupling is hypothesized to define the primary kernel for respiratory rhythm generation in the pre-Bötzinger complex (pre-BötC) in mammals. Two minimal models of these neurons are proposed. In model 1, bursting arises via fast activation and slow inactivation of a persistent Na+ current INaP-h. In(More)
In late summer 1999, an outbreak of human encephalitis occurred in the northeastern United States that was concurrent with extensive mortality in crows (Corvus species) as well as the deaths of several exotic birds at a zoological park in the same area. Complete genome sequencing of a flavivirus isolated from the brain of a dead Chilean flamingo(More)
The mesoderm of amphibian embryos such as Xenopus laevis arises through an inductive interaction in which cells of the vegetal hemisphere of the embryo act on overlying equatorial and animal pole cells. Three classes of 'mesoderm-inducing factor' (MIF) that might be responsible for this interaction in vivo have been discovered. These are members of the(More)
Mouse embryos homozygous for a null mutation in nodal arrest development at early gastrulation and contain little or no embryonic mesoderm. Here, two Xenopus nodal-related genes (Xnr-1 and Xnr-2) are identified and shown to be expressed transiently during embryogenesis, first within the vegetal region of late blastulae and later in the marginal zone during(More)
We have proposed models for the ionic basis of oscillatory bursting of respiratory pacemaker neurons in the pre-Bötzinger complex. In this paper, we investigate the frequency control and synchronization of these model neurons when coupled by excitatory amino-acid-mediated synapses and controlled by convergent synaptic inputs modeled as tonic excitation.(More)