American Journal of Anatomy

doi: 10.1002/aja.1001280301pmid: N/A

Dym, Martin; Clermont, Yves

doi: 10.1002/aja.1001280302pmid: 4193812

In the normal adult rat testis, type A0 spermatogonia do not appear to participate to a significant extent in the production of spermatocytes, while type A1 spermatogonia periodically initiate a series of divisions resulting in the production of spermatocytes and new type A1 spermatogonia.

Hardin, J. H.; Spicer, S. S.

doi: 10.1002/aja.1001280303pmid: 4193813

For ultrastructural study of the formation and maturation of human eosinophil granules, bone marrow and buffy coat specimens were fixed with an aqueous solution of potassium pyroantimonate and osmium tetroxide and by conventional methods. The antimonate‐osmium tetroxide method of fixation, which is thought to permit ultrastructural localization of sodium or other cations, offered an advantage over routine methods in that it permitted recognition of four rather than two varieties of cytoplasmic granules in human eosinophils at various stages of cell development. These four granule varieties, designated A, B, C, and D, differed primarily in distribution and content of crystalloids and antimonate deposits: A granules lacked antimonate deposits and cystalloids; B granules contained a rim of deposits but lacked crystalloids; C granules possessed deposits that were present in the peripheral matrices but not in the central crystalloids; and D granules lacked deposits but contained crystalloids. Evidence is provided that these four varieties of granules represent progressive stages in the maturation of a single granule type and that granules without crystalloids are transformed into granules with crystalloids. The results also provide evidence for the presence of an as yet unidentified pyroantimonate precipitable cation in human eosinophil granules.

Hillman, Nina; Hillman, Ralph; Wileman, Geraldine

doi: 10.1002/aja.1001280304pmid: 4193814

A statistical study of embryos obtained from both spontaneously ovulated and superovulated +/t12 females, mated inter se, shows that the range of the lethal phenocritical period of the t12 allele in a homozygous condition is from the 8–12 cell stage to the early blastocyst stage. The majority of t12 homozygotes are developmentally arrested as late morula and the nuclei of these embryos contain lipid droplets and fibrillo‐granular bodies. These same inclusions are found in other t12 embryos which are developmentally arrested either earlier or later than the late morula stage and distinguish 30–40% of the embryos (presumably t12 homozygotes) from their litter‐mates at the 2‐ and 4‐cell stages. Ultrastructural‐cytochemical studies of the fibrillo‐granular bodies show that the fibrillar areas are sensitive to pepsin and the granules to ribonuclease and are thus structurally and chemically similar to definitive nucleoli. Binucleate cells are also present in a high frequency of t12 homozygous embryos. This condition is considered an additional phenotypic expression of the genotype.

Aterman, K.; Patel, S.

doi: 10.1002/aja.1001280305pmid: 4193815

The occurrence of striated muscle in an “extralobar pulmonary sequestration,” a typical “accessory lobe,” has been described for the first time in an infant with the respiratory distress syndrome of the newborn. The few published cases of the presence of striated muscle in the lungs have been reviewed. In most instances they were associated with benign or malignant tumor formation. The simultaneous occurrence of a pulmonary sequestration and striated muscle is explained by postulating the displacement of a fragment from the lung bud early in its development. This view eliminates the necessity of invoking an additional pathological happening in the sequestrated lung in the form of a “metaplastic transformation” of either smooth muscle or embryonic connective tissue into striated muscle. While a heteroplastic transformation may occur in instances of malignant tumor formation, striated muscle in the developmental anomaly described here may well form on an entirely different basis.

O'steen, W. Keith; Nandy, Kalidas

doi: 10.1002/aja.1001280306pmid: 4193816

Mutant mice are described which have an early developing locomotor difficulty accompanied by definite neuronal changes in the central nervous system. They develop head tremors during the second postnatal week and later action tremors while walking. Seizures occur spontaneously and can be induced by stimulation. By the third or fourth week, they lose the righting reflex. The most apparent neuropathologic sign is the progressive development of nuclear hyperchromasia, especially in the largest neurons of the spinal cord and brain stem. Purkinje cells of the cerebellum are similarly affected. Hyperchromasia occurs in single, isolated neurons scattered throughout the central nervous system, as well as in groups of cells which comprise a brain stem nucelus. Lipofuscin pigment in quantities comparable to that in neurons of 12 months old mice was found in neurons with hyperchromatic nuclei as early as five weeks of age, an observation which suggests that premature aging might be occurring in the mutant's central nervous system.

Yanagimachi, R.; Noda, Y. D.

doi: 10.1002/aja.1001280307pmid: 4193817

The fine structure of the principal components of the sperm head of the golden hamster (Mesocricetus auratus) is described. The acrosome investing the anterior half of the sperm nucleus comprises two regions, the anteriorly located, enlarged region (acrosome cap) and the posteriorly located, thin region (acrosome collar). The acrosome contains substances which are different in electron density. The less electron‐dense material is present in the anterior part of the acrosome cap. The electron‐dense material is located along the outer acrosome membrane of the posterior part of the acrosome cap and also in the acrosome collar. A cytoplasmic element distributed over the surface of the sperm nucleus is abundant in the regions called perforatorium, subacrosomal ring, and post‐nuclear cap. The perforatorium and subacrosmal ring consist of the densely packed cytoplasmic element invested by the inner acrosome membrane. The post‐nuclear cap is a layer of densely packed cytoplasmic element tightly adhering to the overlying plasma membrane. At the time of sperm death in the epididymis, uterus, and physiological salt solution (Tyrode's) the acrosome cap and plasma membrane tend to undergo drastic degenerative changes. On the other hand, the nucleus, acrosome collar, perforatorium, and post‐nuclear cap remain morphologically unchanged in many spermatozoa during the initial stage of sperm degeneration. Comparisons are made of the structures of the acrosome, perforatorium, and post‐nuclear cap of the hamster spermatozoa with those of other mammalian species.