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Biomedical subjects

R Marty

Publications and source records attributed to R Marty.

At least 37 records · Page 2Linked to original sources
PubMed1980

[Bodian process. Ultrastructural study].

The Bodian method was used for an ultrastructural study on the optic nerve of the adult cat in order to compare the effects of two fixation techniques on the normal nerve and on the nerve during Wallerian degeneration after unilateral enucleation. Immersion fixation causes a predominately metallic deposit in the myelin sheath; the perfusion has no effect. During the Wallerian degeneration the two fixation methods lead to a metallic deposit located in the axon which is in large grains after immersion and extremely dense after perfusion. Various diffraction methods were used to identify the nature of the metallic deposit. These results emphasize the positive elements in systemically associating the electron microscope with the optic microscope for studies concerning Wallerian degeneration after metallic impregnation in the central nervous system

Animals↗
PubMed1980

[Myelinization of oligodendrocytes in experimental degeneration of the corpus callosum].

An ultrastructural study of myelinated oligodendrocytes and aberrant myelin sheaths has been carried out on the corpus callosum of the adult rat, undergoing wallerian and retrograde degeneration. Abnormal myelin configurations appear under various forms and may be explained under different processes. In some cases, the collapsed myelin sheaths are closely apposed to the cell body of the oligodendrocyte while in others the sheaths surrounding the glial perikarya are described as redundant myelin sheaths issued from small neighbouring myelinated axons. In most instances, myelin of the compact type consisting of 1 to 5 lamellae or of splitted ones between which invades oligodendroglial cytoplasm, ensheaths completely the oligodendrocytes. Myelination de novo (that is, aberrant myelination) seems to be a correct interpretation of some enwrapping sheaths of myelin but for the other myelinated oligodendrocytes it is suggested that the glial cells penetrate inside previously formed myelin sheaths following the degeneration of the axon.

Animals↗
PubMed1979

[The optic nerve in the cat. I. Quantitative aspects in the adult cat].

A quantitative study was carried out on the adult cat optic nerve near the eyeball by systematically measuring the perimeters of all the axons seen through the optic microscope. The main purpose of this study was to define the topographical distribution of these axons in function of their size. Statistical studies show the existence of an area of maximal concentration of large axons in crescent form situated in the temporal zone of the nerve. The neurophysiological implications are discussed.

Age Factors↗
PubMed1979

[The optic nerve in the cat. II. Qualitative aspects of maturation in the adult cat].

54 healthy cats were studied. In almost all cases, two types of degenerative signs could be seen: in the primary optic pathways, but also in the posterior funiculi and the spinal-cerebellar tracts, lesions of wide-diameter axons seen by their initial demyelination, accompanied by intense neuroglial reactions, and, on the other hand, a Wallerian degeneration of smaller axons situated in the axial part of the nerve. The percentage of these abnormalities must still be evaluated. Their eventual consequences and nature are discussed.

Age Factors↗
PubMed1978

[Postnatal cellular reactivity of the optic nerve after enucleation in the rat. Quantitative aspects in relation to myelinization].

The use of an experimental procedure based upon progressive postoperative delays allowed the quantification of the effects of enucleation performed at the ages of 2, 8 and 20 days, corresponding to key stages of the postnatal maturation of the optic nerve, namely premyelination, myelination and postmyelination. Two main events were noteworthy regarding cell reactivity. The higher the age of the animals at operation, the lower was the proliferation, and the larger was the time lapse between operation and the peak of proliferation. The interferences between reaction gliosis and myelination gliosis depended upon the developmental stage of the optic nerve. This reflects a progressive loss of plasticity.

Age Factors↗
PubMed1977

Ultrasonic evaluation of radiation therapy ports.

Radiation therapy is useful in the palliative treatment of large, unresectable abdominal and pelvic malignancies. The purpose of this study is to evaluate the effectiveness of B mode ultrasound scanning as an adjunct in radiation treatment planning of these patients. Fifty-one patients with large abdominal or pelvic masses had radiation therapy ports established using findings from surgery, radiographs, and physical examination. All the patients then had B mode ultrasound examinations. The position of the therapy ports was marked on the echogram. Thirty-one of the 51 patients studied (61%) had evidence of extension of tumor beyond the therapy ports. This was often due to "iceberging", i.e. when the deep portion of the tumor was considerably larger than the palpable margins of the superficial portion. B mode ultrasound scanning is a valuable adjunct in planning palliative radiation therapy of patients with large, unresectable, abdominal and pelvic malignancies.

Abdominal Neoplasms↗
PubMed1977

[Projections of the cortical visual areas of the posterior gyrus sigmoid and the caudate nucleus in the cat].

The complex performances of the visuo-motor system entail probably an intervention of circuits connecting, the primary visual areas, to other cortical regions, specially the sensory motor cortex, and certain sub-cortical formations. For testing this hypothesis, the unilateral resection of the areas 17, 18 and 19 has been undertaken on 19 cats, with delays ranging from 8 days to 3 months after intervention. The tracing of the pathways was carried out by combining different degenerating methods in particular the Marchi reaction. Based on this, it is possible to define a compact bundle of the axons originating from the primary visual cortex and dividing into two fascicles of unequal magnitude. The slender ends in the lower part of the posterior gyrus sigmoïd; the larger one penetrates into the caudale nucleus. An ultrastructural study specifies the modalities of distribution of the axons within this nucleus.

Animals↗
PubMed1976

The structural maturation of the stato-acoustic nerve in the cat.

The maturation of the stato-acoustic nerve in the cat was studied by light and electron microscopy from the fetal stage to the adult. Measurement of the outer diameter of the fibers and the study of the myelination process revealed that myelination begins earlier for the vestibular nerve than for the cochlear nerve: by the fifty-third day of gestation 64% of the vestibular fibres have already passed the promyelin stage whereas for the cochlear nerve this promyelin stage begins for the majority of fibers on the fifty-seventh gestation day. Afterward, maturation proceeds more rapidly for the cochlear nerve. In the case of both nerves, maturation is still incomplete at two months of age. Concerning the relationship between the thickness of the myelin sheath and the axoplasmic diameter, there is already a good correlation by the fifty-seventh day of gestation in the vestibular nerve, whereas it appears several days after birth in the cochlear nerve.

Age Factors↗
PubMed1976

[Pathways and ascending vestibular projections emanating from primary nuclei: radioautographic study (author's transl)].

A study of the pathways and ascending vestibular projections was carried out in the cat after unilateral injection of tritiated leucine into the rostral vestibular complex. Radioautographic analysis revealed a gradual decline in the density of labeling as ascending fibers were found to progress towards more rostral relays. The pathways and projections were very compact in the oculomotor nuclei, became less intense in the Cajal and Darkschewitsch nuclei, and thinned out considerably until they reached a transitional zone in the thalamus between the ventrobasal and ventrolateral complexes. These results confirm established and previous findings in this laboratory obtained by neurophysiological and neurohistological examination procedures. They provide the first anatomical evidence concerning the existence of vestibulothalamic projections and pathways.

Afferent Pathways↗
PubMed1976

A vestibulothalamic pathway: electrophysiological demonstration in the cat by localized cooling.

Localized cooling was used in the search for vestibulothalamic pathways and a study was made of its effect on the activity of the thalamic neurons brought into action by stimulation of the vestibular nerve. Two cell populations were identified by their distinctive latencies in the ventral part of the posterior thalamus. Short latency responses were transmitted monosynaptically by means of a direct controlateral pathway whose course was identified. For long latency responses, the hypothesis of a polysynaptic path seems probable.

Animals↗
PubMed1976

Bone trauma and related benign disease: assessment by bone scanning.

The radionuclide investigation of skeletal trauma in the past was confined generally to scintimetry and an occasional bone scan. The development of improved radiopharmaceuticals, including 99mTc-labeled compounds with their enhanced sensitivity, and the refinement of imaging devices offering superior resolution and speed have allowed a more detailed assessment of conditions resulting from trauma. Practical approaches to the diagnosis of subtle bone injury resulting in stress fracture, the differentiation between delayed healing and nonunion, and early recognition of avascular necrosis and osteomyelitis are now available. The changing pattern of radionuclide uptake in bone following damage by radiation and other abnormalities as a consequence of trauma also can be easily studied.

Adolescent↗
PubMed1975

The onset of synaptogenesis in rat temporal cortex.

The onset of synaptogenesis was studied in the temporal cortex of rat fetuses whose age ranged between 15 and 19 days of gestation. First synapses were found at a surprisingly early stage of cortical development: on day 16. These contacts showed relatively few vesicles and very inconspicuous membrane-thickenings. They were located in the marginal layer, above as well as below the narrow band formed by the newly arrived first neuroblasts of the prospective corticle plate. The postsynaptic structures were probably dendrites of the horizontally or obliquely orientated neurons scattered throughout the marginal layer (such neurons were seen even within the cell-dense band). On day 17, the cortical plate separated the differentiated cells definitely into a superficial and a deep population. As on the following days, synapses were found above and below the cortical plate but not within it. In addition to contacts showing the same features as those described on day 16, there were already synapses with numerous vesicles and clearly asymmetric membrane thickenings. On days 18 and 19 the borders of the cortical plate became more clear-cut. The well-differentiated neurons situated above and below this plate could now be identified as Retzius-Cajal cells of the prospective molecular layer and as polymorphous cells of the layer VI b respectively. The presence of axo-somatic contacts on these neurons provided direct evidence that both cell types are targets for synapses. Desmosome-like junctions were found even in the youngest fetuses studied. Their roughly symmetric membrane thickenings were clearly more conspicious than those of earliest synapses. Desmosome-like junctions occurred very frequently between structures which subsequently were never seen to become synaptically linked. During the entire period studied, numerous coated vesicles fused with cell membranes were noted. Such "open" vesicles were seen on neurons (sometimes in the immediate vicinity of synapses) but also on non-nervous, extracortical as well as intracortical structures. Thus there does not seem to be a specific relationship between desmosome-like junctions and coated vesicles on the one hand and synapse formation on the other.

Animals↗