The lining cells in the cavernous body, which is a branch of the afferent branchial artery, of lamprey gills were studied with transmission (TEM) and scanning electron microscope (SEM).Adult and larval lampreys, Lampertra planeri, were used in this study. Lamprey gills removed after perfusion were fixed in 2 % glutaraldehyde/formaldehyde (pH 7. 4) for 1 hour and postfixed in 1 % osmic acid. For TEM, the gills were dehydrated in ethanol and embedded in epon 812. Ultrathin sections were doubly stained with uranyl acetate and lead citrate. For SEM, most of the gills were dehydrated in ethanol and isoamylacetate and cracked in liquid nitrogen. Some of the gills dehydrated were embedded in stylene monomer. Stylene embedded blocks were cracked with a hummer and dissolved in propylene oxide. All the specimens were dried in a critical point dryer and coated 100 Å thickness with gold-paladium.The cavernous body is composed of trabeculae, between which are blood spaces, the lacunae.
Estimation of Total Number of Nucleated Cells in the Bone Marrow of Young Adult Albino Rats.* In this laboratory we have been studying the quantitative aspects of the lymphocyte production in the thymolymphatic tissues of albino rats (OSOGOE et al. 1957). Along with such studies, detailed studies on the production of blood cells in the bone marrow are also being performed. In this paper we wish to present the results of some determinations on young adult albino rats conducted along this line of investigation. I. Material and Methods. Forty-one WISTAR strain albino rats weighing around 200g served as the material. They were taken from the laboratory colony maintained on the standard stock diet.** In the present study it was of particular importance to employ test animals under comparable nutritional conditions and with almost identical body weights, for it is often observed that the cellular density or the rate of cell multiplication may vary, to a fairly considerable extent, depending upon the nutritional conditions and the monthly (or even weekly) age of the animal.
Summary
The histological features of the regional lymph node draining a skin homograft have been examined in normal and tolerant recipients. The response of this node was morphologically identical in normal and specifically tolerant hosts, the most important feature being the appearance of medullary cords packed with intensely pyroninophilic cells. Furthermore, a similar response was observed in the regional lymph nodes of (DA × Lewis)F1 hybrids bearing DA skin grafts of which they were “genetically tolerant”. It was concluded that the failure of graft rejection in tolerant rats could not be attributed to an absence of reactivity to the grafts on the part of the lymphoid tissue of the host.
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