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Biomedical subjects

J Armand

Publications and source records attributed to J Armand.

At least 55 records · Page 3Linked to original sources
PubMed1980

Cells of origin of crossed and uncrossed corticospinal fibers in the cat: a quantitative horseradish peroxidase study.

The cortical distribution of the cells of origin of the dorsolateral and the ventral corticospinal tracts were studied in cat. This was done by making subtotal spinal transections, which in different experiments spared different portions of one ventral or one lateral funiculus at C5--C7. One week later horseradish peroxidase (HRP) injections were made one segment caudal to the lesion and the cortical distribution of the HRP labeled neurons was studied. Thus, it was found that the dorsolateral corticospinal tract at C5--C7 is composed of crossed and uncrossed fibers in a ratio of about 10 : 1, while the ventral corticospinal tract, which contains much fewer cortical fibers, is composed and uncrossed fibers in a ratio of approximately 1 : 1. Further, the primary motor cortex (area 4) was found to contribute fibers to both the crossed and the uncrossed dorsolateral corticospinal tract as well as to both the crossed and the uncrossed ventral corticospinal tract. The primary somatosensory cortex (area 3a, 3b, 1--2, 5a, 5b) as well as the secondary somatosensory cortex (area 2 pre-insularis), on the other hand, were found to contribute fibers mainly to the crossed dorsolateral tract. Area 4 was found to display a further organization, such that it contains a medial and a lateral part, both of which contribute mainly fibers to the crossed dorsolateral tract, while the remainder of area 4 contributes fibers to the crossed and uncrossed dorsolateral as well as to the crossed and uncrossed ventral tracts.

Animals↗
PubMed1980

Hemolymph acid-base balance of the crayfish Astacus leptodactylus as a function of the oxygenation and the acid-base balance of the ambient water.

The acid-base balance of the prebranchial hemolymph of the crayfish Astacus leptodactylus was studied at various acid-base balances and levels of oxygenation of the ambient water at 13 degrees C. The water acid-base balance was controlled automatically by a pH-CO2-stat. Into water of constant titration alkalinity, TA, this device intermittenly injects carbon dioxide to maintain the pH at a preset value. Water pH was reduced to the same value either by hypercapnia (at constant TA) or by adding HCl or H2SO4 to decrease the TA (at constant CO2 tension). Decrease of hemolymph pH and increase of hemolymph PCO2 were similar for the three acidic waters. Water oxygenation changes strongly affected hemolymph ABB. In crayfish living in hyperoxic water (PO2 congruent to 600 Torr) compared to those in hypoxic water (PO2 congruent to 40 Torr), hemolymph pH was 0.3 to 0.4 unit lower and hemolymph PCO2 several times higher, the exact values of pH and PCO2 depending on the controlled ambient acid-base balance. In any study of the hemolymph acid-base balance of the crayfish, it is an important to control ambient water's acid-base balance and oxygenation as it is to control its temperature, a conclusion which probably holds true for studies on all water breathers.

Acid-Base Equilibrium↗
PubMed1978

Topical versus diffuse organization of the corticospinal tract in the cat.

1. The organization of the corticospinal system has been studies, in the cat, using electrophysiological techniques (stimulation of the lateral corticospinal tract at different spinal levels, recording in the contralateral cortex by means of transcortical bipolar electrodes) and anatomical techniques (HRP injection localized in the grey matter of a chosen spinal level). These two approaches give complementary results. Different cortical zones can be defined according to their spinal projections. 2. Some restricted cortical zones are at the origin of only contralateral corticospinal projections specific to a given spinal enlargement, cervical or lumbar. 3. Other larger cortical zones are at the origin of bilateral spinal projections specific to a given spinal enlargement, at least in the case of the cervical one. 4. Finally, a cortical zone is at the origin of bilateral cortical projections both to the cervical and lumbar enlargements. The question of multiple branching of individual cortisospinal neurons is considered, but cannot be answered using out techniques.

Animals↗
PubMed1977

[Organization of contralateral and bilateral projections of corticospinal tracts in cats].

In Cats with a previous spinal lesion (C 6) saving only a lateral or ventral funiculus, a caudal horseradish peroxidase injection (C 8-Th 1) reveals that some cortical zones (lateral sigmoïd gyrus, medial part of the posterieur sigmoïd gyrus, medial part of the dorsal bank of the cruciate sulcus) send spinal projections, only contralaterally, by way of the dorsolateral funiculus, whereas other cortical zones (anterior sigmoïd gyrus, middle part of the posterior sigmoïd gyrus, lateral parts of the dorsal and ventral bank of the cruciate sulcus) send bilateral spinal projections by way of the ventral and dorsolateral funiculi.

Animals↗