Cat Mesentery Research Articles

Enteric plexus fibers in the mesentery of cats, dogs and rabbits.

Enteric plexus fibers in the mesentery of cats, dogs and rabbits.

Vascular effects of hypertonic solutions.

During the course of an investigation into the treatment of metabolic acidosis arising from total body perfusion, it was noticed that the intra-arterial administration of concentrated alkalies resulted in a fall in arteriovenous pressure difference at constant flow. A similar decline in peripheral resistance could be produced by hypertonic sugar and salt solutions. This response was found to be independent of the central nervous system. The role of the vasodilatation in the complex vasomotor reaction to the rapid intravenous injection of hyperosmotic agents was then investigated in the intact and vagotomized dog. It was found that when concentrations of up to 1,500 mOsm./L. were used, the predominant response was a delayed hypotension consistent with peripheral vasodilatation. This reaction was complicated by preliminary pulmonary hypertension when solutions containing more than 2,000 mOsm./L. were administered. Twenty per cent NaCl produced such a severe initial phase that the animals frequently died from acute cor pulmonale. The site of obstruction to blood flow through the lungs was variable. Fifty percent glucose could incite pulmonary hypertension, but urea was anomalous in that it was never observed to produce pulmonary vascular effects. Studies in the isolated perfused lung indicated that, again with the exception of urea, all solutions with an osmolarity equal or greater than 5 per cent NaCl evoked pulmonary hypertension. The increase in pulmonary vascular resistance was transitory in spite of recirculation. No response could be elicited when red cells were absent from the perfusate even though, under these conditions, the lung was still sensitive to serotonin. Microscopic examination of the circulation through the brain, lung, mesentery and thigh of both cat and dog demonstrated that intravascular red-cell agglutination occurred after regional arterial injection of highly concentrated salt and sugar solutions. This alteration in the stability of the red-cell stream is considered to be responsible for the obstructive effects of hyperosmotic agents previously attributed to vasospasm.

Observations on the so-called sex chromatin.

In an investigation concerning some cytological aspects of the problem of sexual dimorphism of intermitotic nuclei in some mammals, as discribed originally by Barr and his associates, the following facts were established. 1. A corpuscle, here called “Barr's corpuscle” can be found in about 75% of the nuclei in 5 μ sections of adreneal cortex of the female cat, stained by Feulgen's method. It can be recognised by characteristic morphological features and is found only in female individuals. Chromatin bodies of similar size in nuclei of male individuals are found in 6–10% of the nuclei of male adrenocortical tissue. They have a variable size and aspect and could not be distinguished cytologically from chromatin particles occurring, independently of Barr's corpuscle, in cell nuclei of female individuals. 2. When only nuclei are counted which are not touched by the microtome knife (thick sections), Barr's corpuscle was found in 97% or more of the nuclei of adrenal cortex of the (female) cat. In total preparations of the mesentery of female cats this element, as a rule in bipartite form, was found in 97–99 % of the mesothelial nuclei, in the same material of female rabbits in 99–100%. In oral mucosal smears the disappearance of Barr's corpuscle was shown to go parallel with degenerative changes in the nuclei of the desquamated epithelial cells, in tissue culture preparations to be accompanied by progressive abnormality in the karyotype. 3. In the prophase of the mitotic division of female nuclei an element, corresponding in aspect and size to Barr's corpuscle in intermitotic nuclei of the same kind can be observed. In later stages of mitosis it is lost between the other chromosomes. In the telophase it reappears as a dark staining element between the decondensing chromosomes in each of the two daughter nuclei. 4. In nuclei of male individuals, neither in intermitotic nuclei nor in the prophase, a separate element could be found with a morphological behaviour similar to Barr's corpuscle. The chromatin bodies of similar size to the latter, found in a part of small and intermediate nuclei (especially frequent in the rabbit) seem, in the hydropic nuclei of mesothelial cells, to be broken up into smaller elements and are lost in the whole chromatin pattern. The same is the case with corpuscles of the same kind in female nuclei, found independently of Barr's corpuscle. 5. Barr's corpuscle shows a massive, rounded aspect in small nuclei with a coarsely granular chromatin. Under the electron microscope it is seen in this form as a homogenous mass. In large, hydropic nuclei it occurs mainly as two rod-shaped elements lying near to each other in different positions; each of them sometimes shows a bi-filamentous structure. In the mammals examined here (man, cat and rabbit) there is a similarity in form and size between these rodshaped elements of the corpuscle of Barr in „unfolded“ form and the X-chromosome of the mammals concerned, as described in the cytogenetical literature.

Staining Nerve Fibers with Methylene Blue. An Evaluation of Variables Used in An Immersion Technic

A study of the effects of osmotic pressure, pH, the presence of dextrose, acetate, pyruvate or lactate, and agents affecting cell permeability during supravital staining by methylene blue was made by means of an immersion technic. Mesentery and intestine of dogs and cats were used. Penetration of the dye was limited to the mesentery and more superficial layers of intestine. Conditions which facilitated the characteristic differentiation of of nerve fibers were: continuous oxygenation of the staining solution, pH about 5.6 stabilized by phosphate buffer, and the presence of small amounts of acetate and lactate. Young animals' tissue stained better than old. Methylene blue was a much more effective staining agent than less completely methylated thionins.