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P H Bonner

Publications and source records attributed to P H Bonner.

15 recordsLinked to original sources
PubMed1997

The oculomotor periphery: the clinician's focus is no longer a basic science stepchild.

The study of the oculomotor periphery, the extraocular muscles and their orbital attachments, is undergoing a rapid expansion. This is an important progression for both basic and clinical communities as, for too long, the ophthalmologist has worked primarily in the periphery and the basic researcher has been occupied with study of the central components of the oculomotor system. From recent studies, it is clear that the morphology, cell and molecular biology, and genetics of the eye muscles and their corresponding motoneuron pools, and muscle attachments within the orbit are more complex than has heretofore been appreciated.

Animals↗
PubMed1994

Botulinum A toxin stimulates neurite branching in nerve-muscle cocultures.

In addition to skeletal muscle paralysis, type A botulinum toxin commonly causes sprouting of motor axons in various experimental whole-animal systems. The use of type A botulinum toxin in clinical treatment of muscle spasm disorders is becoming increasingly popular. The eventual, unwanted return of involuntary activity in the treated muscles may be a consequence of such axon sprouting. We have developed a coculture model allowing the quantification of botulinum toxin-induced sprouting that shows promise for future studies on its mechanism and control. Chick embryo ciliary ganglion motor neurons were cocultured with chick leg muscle cells. The presence of type A botulinum toxin in the coculture medium was correlated with significantly increased branching frequency of neurites. Toxin-increased branching frequency occurred even when the neurons and muscle cells were separated from each other on the culture dishes, suggesting a presynaptic effect of toxin. Cocultures incubated in the presence of curare, a post-synaptic blocker, had control levels of neurite branching, ruling out the possibility that simple synaptic blockade causes sprouting but again supporting the hypothesis of a pre-synaptic activity of botulinum toxin.

Animals↗
PubMed1989

Correlation of development stage and gap junction formation between chick embryo neurons and cloned skeletal muscle myoblasts.

The frequency of gap junction formation between neurons and myoblasts of chick embryo leg skeletal muscle changes as a function of the developmental stage of the muscle. Cells from leg muscle of various ages and states of innervation were first cloned in vitro and then co-cultured with ciliary ganglion, spinal cord, or dorsal root ganglion neurons. The presence of gap junctions between cells was identified by the passage of fluorescent dyes or electric currents from one cell to another. The clones examined were fusing muscle clones (myoblasts) as well as nonfusing clones. Mononuclear cells of either kind of clone derived from legs younger than stage 24 (E4) dye-couple with other clone cells but do not dye-couple with neurons. Myoblasts of fusing muscle clones derived from stage 24 through stage 29 (E5) legs dye-couple with neurons at high frequency; nonfusing clones from these same embryos do not contain cells that dye-couple with neurons. Mononuclear cells of both fusing and nonfusing clones from normally innervated stage 30 (E6) through 38 (E12) legs do not dye-couple with neurons at significant frequencies. Additionally, aneural legs of denervated E10-E12 embryos yield muscle clones in which the myoblasts again dye-couple with neurons at high frequency. The ability to form communicating junctions between muscle cells and neurons in culture is restricted to myoblasts cloned from legs of those stages of development and conditions of innervation that define and limit neuron-dependent alteration of myoblast populations in vivo.

Animals↗
PubMed1988

Gap junctions form in culture between chick embryo neurons and skeletal muscle myoblasts.

Possible mechanisms by which neurons can affect the differentiated states of mononucleated cells in the early chick embryo leg skeletal myogenic lineage are being investigated. Under conditions of co-culture known to promote inductive interactions between embryonic neurons and leg cells, spinal cord neurons and mononucleated leg cells are coupled by gap junctions as shown by cell-to-cell passage of Lucifer yellow and hyperpolarizing or depolarizing currents. Co-cultures composed of ciliary ganglion neurons and clones of leg cells showed that the ability to form gap junctions with neurons is a differentiated function of myoblasts. Dye-coupling with neurons was found at high frequency only when the partner cell was a myoblast of a differentiating muscle clone. Myoblasts in undifferentiated clones formed gap junctions with each other but not with neurons. The nature of the junction-forming neuron is not restricted since neurons from spinal cord, ciliary ganglion and dorsal root ganglion all readily form junctions with myoblasts.

Animals↗
PubMed1987

Myoblast differentiation is induced by nerve transplanted to chick embryo legs.

Chick embryos were denervated early in development in order to disrupt the normal inductive interactions between the nervous system and developing populations of mononucleated myoblasts and their precursors in the leg. Neural tissue, either spinal cord or ciliary ganglion, was transplanted to one leg of the denervated embryos; the other leg remained aneural. Clonal analysis of cell populations in the transplant-containing legs showed that ectopic nerve tissue can recapitulate some of the neuromuscular interactions that occur in normally developing embryos. Chief among these was the observation that transplantation induced the appearance of the CMR-III myoblast class in the leg muscle. Since the process by which CMR-III myoblasts are produced from a precursor is dependent on nerve both in vivo and in vitro (Bonner, P.H. and T.R. Adams, Dev. Biol., 90:175-184, 1982), it was concluded that transplanted nerve tissue can also induce myoblast differentiation.

Animals↗
PubMed1980

Developmental fate of a distinct class of chick myoblasts after transplantation of cloned cells into quail embryos.

A technique appropriate to investigation of the developmental fates of distinct embryonic cell types is described and the fate of a particular type of chick myoblast (CMR-I) examined. CMR-I myoblast clones are morphologically different from other chick myoblast clone types and can readily be identified in living cultures. After two weeks of culture CMR-I myoblast clones were collected, aggregated, and transplanted into the prospective dorsal thigh region of young quail embryos. After four days of growth, cells of the transplant-containing quail legs were grown as clones. Chick clones were located by Feulgen staining and identified as muscle or non-muscle and, if muscle, as CMR-I or not; 91% of the chick clones recovered from transplants were muscle clones, and of these 97% were CMR-I. It was concluded that CMR-I myoblasts do not undergo a change in differentiated state identifiable by clonal analysis. Other transplant-containing quail legs were fixed, sectioned, and Feulgen stained. The locations of chick nuclei were determined. The only region in which chick nuclei appeared at significantly greater frequency than in control tissue was the dorsal thigh muscle, the region into which the cloned chick cells were placed originally. Dorsal thigh multinucleated myotubes exhibited the highest percentage of chick nuclei of all tissues examined. It was concluded that the fate of CMR-I myoblasts is fusion to form myotubes.

Animals↗
PubMed1974

Intermediates of bacteriophage MS2 assembly in vivo.

The in vivo process of virion assembly was studied in rifampin-treated, MS2-infected Escherichia coli during late times of infection-after 18 min postinfection. Differential sucrose gradient sedimentation of infected-cell lysates taken at various times after radioactive labeling indicated a definite temporal order of appearance of phage-specific protein in assembly-related structures. Labeled MS2 protein appears first as a low-molecular-weight peak at the tops of gradients, then as a peak at 40S and as a large number of almost unseparable structures between 40 and 80S, and finally as 80S mature phage particles. During the chase of a short labeling period, radioactive phage protein was found to disappear from gradients in the same temporal order as it appeared; the soluble peak disappears first, followed by the 40 to 70S region. The chased label appears quantitatively in the 80S phage peak. Labeled phage RNA was found to appear first in the 40S peak, then in the structures between 40 and 70S, and finally in 80S phage particles. The order of disappearance of labeled phage RNA during a chase is the same as its appearance. Resedimentation of the 40 to 70S region indicated the presence of distinct structures at 60 and 70S and many indistinct ones between 40 and 60S. The smaller intermediates exhibit separable maturation protein-rich and coat protein-rich segments, indicating nonrandom binding of the two proteins during the initial steps of assembly. Larger, discrete intermediates appear at 60 and 70S. Treatment of the various structures with pancreatic RNase results in destruction of those from 40 through 60S; treatment of the 70S structure results in the conversion of some of it to a 45S peak, presumably the complete capsid. A small fraction of the 80S phage peak is also sensitive to RNase, resulting in a similar 45S peak. Pulse-chase experiments indicate that structures from 40 through 60S as well as the RNase-sensitive 70S structure are assembly intermediates, but that the RNase-insensitive 70S and the RNase-sensitive 80S structures are not.

Carbon Radioisotopes↗
PubMedDate not supplied

Myoblast transfer therapy in the treatment of ptosis: a preliminary study.

Congenital ptosis with poor levator function is now managed by frontalis suspension techniques. While this procedure is better than those used in the past, serious shortcomings exist. A technique producing more normal lid function would be a beneficial addition to surgical management. Since congenital ptosis is thought to be a focal myopathy, we investigated the potential of myoblast transfer therapy in myopathic levator palpebrae superioris. Satellite cells harvested from temporalis muscle were grown as clones, labeled with Dil, and transplanted into experimentally myopathic levator muscle of the same animal. Within 2 weeks, the injected cells were found to be incorporated into muscle fibers within the levator basal lamina. The control side appeared myopathic with very little muscle regeneration. The presence of Dil labeled muscle fibers in the experimental muscles strongly suggests their origin from the injected cells. Electron microscopy of nearby sections showed these fibers to be maturing striated muscle. We feel that the development of this technique may make autogenous myoblast transfer therapy a useful treatment for congenital ptosis and other focal myopathies.

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