American Journal of Anatomy

doi: 10.1002/aja.1001410101pmid: N/A

Hiatt, James L.; Gartner, L. P.; Provenza, D. V.

doi: 10.1002/aja.1001410102pmid: 4853244

Odontogenesis was studied in the Mongolian gerbil (Meriones unguiculatus) molar from the dental lamina stage of development to the appositional stage. Fertilization, determined by vaginal lavage technique, was counted as day 0. Prior to the eighteenth post‐coital day no dental primordia could be detected. Beginning on day 18, pregnant females were sacrificed and the fetuses were decapitated. The heads were frozen and sectioned in a cryostat. The tissue was stained, dehydrated, cleared, and covered. Light microscopy was utilized in evaluating molar odontogenesis. Odontogenesis of the molar began at the dental lamina stage on day 18 followed by the bud stage on day 19 prenatal. The cap stage of development was observed on day 19 or 20. Development of the bell stage was noted on day 22. By the fourth postnatal day, the first molar had reached the appositional stage of development. Development of molars in the gerbil resembles that in other rodents.

Miller, M. L.; Murthy, L.; Basom, C. R.; Petering, H. G.

doi: 10.1002/aja.1001410103pmid: 4850486

Morphometric analyses of liver parenchymal cells were performed on male albino rats fed a semipurified diet supplemented with two levels of copper and zinc. These metals were administered in demineralized drinking water to four groups of animals at two levels. (1) 0.25 μgm Cu/ml, 2.5 μgm Zn/ml, and (2) 1.0 μgm Cu/ml, 10 μgm Zn/ml. Cadmium, also administered in the drinking water daily to rats at 17.2 μgm cadmium/ml, was given to one group of animals on each of the two semipurified diets. Two groups of rats were given laboratory chow plus 17.2 μgm Cd/ml for 71 days and for 280 days.

Rosse, Cornelius; Trotter, John A.

doi: 10.1002/aja.1001410104pmid: 4851246

The morphogenetic events of erythroid differentiation in guinea pig bone marrow were studied by electron microscopy. The diaminobenzidine (DAB) reaction and radioautographic detection of Fe55 incorporation permitted a more objective identification of erythroid cells than was possible in previous studies. With the combined use of these two methods morphological events of cell maturation could be correlated reliably with cytoplasmic hemoglobin content, thus providing a basis for the description of various maturation stages.

Mori, Hiroshi; Matsumoto, Keishi

doi: 10.1002/aja.1001410105pmid: 4368535

Adrenocortex‐like cells were consistently found in the mesovarium or in the hilus of the ovary of rabbits less than three months old. The adrenocortex‐like cells occurred usually in the form of nodules among or near the mesonephric tubules. But they sometimes appeared within the rete ovarii either in direct contact with the epithelial cells or scattered in the stroma. Similar cells were newly formed in the ovarian medulla of one‐month‐old rabbits following injection of ACTH (adrenocorticotropic hormone).

Weber, Dennis F.; Eisenmann, Dale R.; Glick, Paul L.

doi: 10.1002/aja.1001410106pmid: 4604696

Unaltered mature enamel and partially demineralized mature enamel from the cervical third of human permanent teeth were examined by means of transmission electron microscopy, microradiography, phase contrast and Nomarski differential interference microscopy. The Retzius lines in the outer third of the cervical enamel had a staircase configuration. The steps in the stair‐case pattern formed the bases of triangular regions which were radiolucent and ultrastructurally contained fewer crystallites than the adjacent enamel. In the outer prismless layer, the Retzius lines had a curvilinear configuration and were also crystallite deficient. The structure of the Retzius lines in the inner portion of the cervical enamel was not nearly as well defined.

English, Kathleen B.

doi: 10.1002/aja.1001410107pmid: 4850923

Type I mechanoreceptors (also called Haarscheiben or “domes”) are small elevations on the cat's skin, each being supplied by a myelinated sensory fiber. The fiber terminates in apposition to specialized receptor cells (Merkel cells) lying at the base of the epithelium investing the structure. When a group of domes was injured some of the neighboring domes became structurally altered as determined by light and electron microscopy. The changes observed resembled those which accompany denervation and involved the loss of Merkel cells and their apposed sensory nerve terminals from the dome. Since this trauma was produced indirectly it has been called secondary injury. Cells showing some of the morphological features of both keratin‐producing epithelial cells and Merkel cells were observed in secondarily injured domes and in non‐injured domes. The presence of such transitional cells suggests that Merkel cells may be derived from keratinocytes.

Simpson, L. O.

doi: 10.1002/aja.1001410108pmid: 4854498

The relationship of age and body weight to thymus weight in mature NZB mice is reported. Multivariate analysis of data obtained from nearly 1000 mice shows that the decrease in the weight of the thymus, which occurs during thymic involution, may be represented by a smooth curve which flattens out about the twentieth lunar month of age. NZB mouse thymus weight does not appear to be influenced by Coombs test positivity and involution patterns are similar to those of non‐autoimmune mouse strains.

Listgarten, Max A.

doi: 10.1002/aja.1001410109pmid: 4212399

A new type of intercellular junction was observed between adjacent gingival epithelial cells. The junction appears to be composed of two hemidesmosomes facing one another, with the intervening space occupied by basement lamina material. It is distinctly different from desmosomes or any other intercellular junction described thus far. It is perhaps significant that the combination of two hemidesmosomes into a junction may not result in the creation of a desmosome, but of a rather distinct anatomical structure.

Wilbur, Donald L.; Worthington, W. Curtis; Markwald, Roger R.

doi: 10.1002/aja.1001410110pmid: 4369411

Dibutyryl cyclic adenosine monophosphate (4.6 x 10−7M) was infused with a microcannula into hypothalamo‐hypophysial stalk portal vessels of adult male rats. Anterior pituitary glands were prepared for electron microscopic examination at 1, 5, 15, 30 and 60 min after microinfusion. Ultrastructural observations give evidence of stimulated protein synthesis, and emiocytosis. Emiocytosis occurs at 1, 5 and 15 min only. Evidence of protein synthesis does not develop until 15 min. It persists through the 30 min time period. These observations suggest that dbcAMP may be a potent stimulus to protein synthesis, and may be a sufficient stimulus for emiocytosis.