Thalamic mediation of hypoxic respiratory depression in lambs.

Immaturity of respiratory controllers in preterm infants dispose to recurrent apnea and oxygen deprivation. Accompanying reductions in brain oxygen tensions evoke respiratory depression, potentially exacerbating hypoxemia. Central respiratory depression during moderate hypoxia is revealed in the ventilatory decline following initial augmentation.

Peter Mark Roget: physician, scientist, systematist; his thesaurus and his impact on 19th-century neuroscience.

Peter Mark Roget (1779-1869) is best known for his Thesaurus, a project completed late in his long life. He trained as a physician, practiced medicine, and was interested in many branches of science. Much of his life was dedicated to the systematization of knowledge and identifying relationships.

Golgi in retrospect: a historiographic examination of contextual influence in tracing the constructs of neuronal organization.

The concepts underlying the connectivity of neurons and the dynamics of interaction required to explain information processing have undergone significant change over the past century. A re-examination of the evolution of the modern view in historical context reveals that rules for connectivity have changed in a manner that might be expected from critical analysis enabled by technical advance. A retrospective examination of some germane issues that moved Camillo Golgi to question the widely held dogma of his era reveals network principles that could not have been recognized a century ago.

Whither withered Golgi? A retrospective evaluation of reticularist and synaptic constructs.

The 100th anniversary of the shared first Nobel prize in neuroscience by Camillo Golgi and Ramon y Cajal invites reappraisal of the merits of the arguments adduced by these two combative scientists in the light of contemporary knowledge. Guided by cogent reasons for reluctance in accepting the inviolable polarity principle of the neuron doctrine and concern for explaining cerebral recovery of function, Golgi joined the 'reticularists' of his generation. Modern observations of axo-axonic and dendro-dendritic synapses, gap-junction interconnections, rules for the direction and mode of analog or impulse conduction, the myriad diversity of ion channels and gating principles and the complexities of synaptic plasticity have eclipsed the polarized neuron doctrine explanations of reflex physiology and the 'fixed and immutable' connections successfully championed by Cajal.

The sensory neuron and the triumph of Camillo Golgi.

While Golgi's concept of the sensory neuron provided sound reasons for his rejection of the polarity principles underlying the 'neuron doctrine', it is now apparent that his concern about recovery of function after injury and the vast modern findings of ephemerality of connexin-clustered connections in the cerebral cortex and elsewhere in the central nervous system, and credibly termed 'reticularist', has somewhat eclipsed the polarized neuron doctrine of reflex physiology with the "fixed and immutable" connections championed by Cajal. Although Golgi's view was not the result of incisive reasoning based on subsequently confirmed observation, both principles espoused by these combatant Nobel laureate partners have proven robustly operative in different spheres and time frames of neural activity that have vastly enhanced contemporary understanding of neural connectivity.

An early illustrated comparative anatomy of the brain: Samuel Collins' A Systeme of Anatomy (1685) and the emergence of comparative neurology in 17th century England.

The concept of comparing of the brains of various animals and of individual human brains was launched in the last half of the 17th century in England and was much influenced by the formation of the European scientific societies and their attempts to guide naturalist observations into a new systematics. An ambitious attempt to document this trend in an extensively illustrated work of encyclopedic pretensions was the singular publication of Samuel Collins (1618-1710), an energetic anatomist and president of the Royal College of Physicians. His little known tow-volume folio presentation, written in teh vernacular for broad acceptance, contains the seeds of a science of comparative neurology with the largest collection of brain illustrations (as well as of other organ systems) attempted in his era.

Edward Tyson's 1680 account of the 'porpess' brain and its place in the history of comparative neurology.

Edward Tyson (1650-1708), a prominent London physician and an early fellow of the Royal Society is best known for his several anatomical contributions in the creation of primatology, including the preputial and coronal mucilaginous glands (Tyson's glands), later described by Alexis Littré. He also published the first comprehensive account of a single animal (the 'porpess') and placed it in the context of a systematic and experimental methodology. This rare monograph accounts for the contention that Tyson was the founder of comparative anatomy in England, by using this 'fish' to better understand the human condition.

Axonal terminals of sensory neurons and their morphological diversity.

The application of electron microscopy to defining the fine structural characteristics of axon terminals and synapses was followed by a half century of intensive exploration of the molecular concomitants of synaptic activity. The summer of 2003 marks the 50th anniversary of the earliest accounts of synapses by Palay and Palade. Prompted by recent findings of specialization in the fine structure of nociceptor terminals that lack contacts remotely resembling a synapse, we present a survey of arrangements, contacts and axoplasmic contents of peripheral sensory axon terminals.

Electrical stimulation of the posteromedial thalamus modulates breathing in unanesthetized fetal sheep.

Having previously shown that lesions in the posteromedial group of thalamic nuclei abolish hypoxic inhibition of fetal breathing, we devised this study to identify thalamic loci that depress breathing by focal stimulation of specific sectors of the caudal thalamus and adjacent structures. Multipolar electrode arrays consisting of a series of eight stimulation contacts at 1.25-mm intervals were implanted vertically through guide cannulae into the caudal diencephalon of 12 chronically catheterized fetal sheep (>0.

Nociceptor structural specialization in canine and rodent testicular "free" nerve endings.

The receptive fields (RFs) of polymodal nociceptor units of canine testis consist of small fascicles of branching axons ending as clusters within the thin vascular layer overlying the seminiferous tubules. This propitious arrangement enabled serial reconstruction of electron micrographs of a flat, punctate zone, identified during recording of impulse discharge of a single physiologically characterized nociceptor "unit." The RFs showed multiple axons, with some branching and sequential vesicle-containing swellings, similar to what have been called terminals and assumed to constitute impulse generating sites in other tissues.

Genetically-targeted and conditionally-regulated ablation of astroglial cells in the central, enteric and peripheral nervous systems in adult transgenic mice.

Ablation of tissue regions, specific genes, or specific cell types represent important means of studying function in the nervous system. Here we summarize recent experience using a strategy for the genetically-targeted and conditionally regulated ablation of astroglial cells in different parts of the nervous system. The strategy is based on the targeted expression of herpes simplex virus thymidine kinase to astroglial cells using the glial fibrillary acid protein promoter in transgenic mice, combined with treatment with the antiviral agent ganciclovir.

Fixed-diameter polyethylene cuffs applied to the rat sciatic nerve induce a painful neuropathy: ultrastructural morphometric analysis of axonal alterations.

Polyethylene cuffs of varying inner diameters were applied to the rat sciatic or sural nerve with the aim of inducing a standardized nerve injury, as assessed by morphometric analyses of fiber-size spectrum alterations, associated with behavioral manifestations of neuropathic pain. The temporal sequence of axonal degeneration and regeneration was examined in parallel with behavioral analyses of pain initiation and recovery over a 6-week postoperative (PO) period. Cuffs of 0.