American Journal of Anatomy

doi: 10.1002/aja.1001500301pmid: N/A

Mollenhauer, Hilton H.; Morré, D. James

doi: 10.1002/aja.1001500302pmid: 930855

Structures superficially resembling dictyosomes were present in guinea pig primary spermatocytes and in spermatids in late stages of development. The dictyosome‐like structures (DLS) were composed of 2 to 17 saccules. Each saccule averaged about 20 nm in thickness (membranes plus lumen) and 400 nm in diameter and was separated from adjacent saccules in a stack by an intersaccular space of about 12 nm. Single saccules separated from the DLS were also present. Tubules up to 60 nm in diameter were continuous with the edges of the saccules and sometimes extended for several micrometers into the cytoplasm. The membranes of the tubules appeared similar to the saccule membranes. Some DLS saccules and tubules had coated vesicles attached to them.

Spyropoulos, Meropi N.

doi: 10.1002/aja.1001500303pmid: 930856

The purpose of this investigation was: (a) to study the developmental relationships of the temporal muscle and the coronoid process during the critical initial stages of morphogenesis and (b) to correlate the developmental stages of the muscle and the bone with data describing the functioning of the muscles of mastication in utero.

Bruni, J. E.; Montemurro, D. G.; Clattenburg, R. E.

doi: 10.1002/aja.1001500304pmid: 337791

The morphology of the ependymal surface of the rabbit third ventricle was studied following intraventricular injections of an ovulatory dose of synthetic LH‐RH. Identically treated rabbits that received injections of saline, only, served as controls. Animals from both groups were killed 5 minutes and 15 minutes after the injections. The ependyma of the dorsolateral ventricular wall and transitional zone maintained a constant appearance from animal to animal regardless of treatment or time of autopsy. The uniformly non‐ciliated ependyma of the ventrolateral wall and floor (infundibular and mammillary recesses) of the ventricle, however, not only exhibited an appearance quite distinct from either the dorsolateral wall or transitional zone, but also exhibited a transient responsiveness to LH‐RH treatment. In the controls, most ependymal cells of this region bulged conspicuously into the ventricle. Numerous pleomorphic knob‐ of bleb‐like protrusions and occasional microvilli characterized their apical membranes. In contrast, marked changes were seen in the character of the ependymal surface of animals killed five minutes following LH‐RH administration. These changes, which principally took the form of numerous irregular microvillous eruptions of the apical membrane, pervaded the rostrocaudal extent of the infundibular and mammillary recesses. Equivalent regions of the ependymal surface in animals killed 15 minutes after LH‐RH administration, however, were similar to those of the controls. These transient morphological changes observed in the ependymal surface of the ventrolateral wall and floor of the ventricle five minutes after LH‐RH injection may reflect structural modifications associated with absorption of the hormone across the ependymal‐CSF interface.

Taylor, A. B.; Kreulen, David; Prosser, C. L.

doi: 10.1002/aja.1001500305pmid: 930857

Electrotonic spread of applied potentials was observed between longitudinal and circular muscle layers of the small intestine with no rectification. Nexal junctions were demonstrated between muscle fibers of each layer. Connective tissue cells bridged between the two muscle layers. These showed structural characteristics of fibrocytes and of interstitial cells. Some nexuses were seen between connective tissue cells and between these cells and muscle fibers of each layer but in most junctions the membranes were 10–18 nm apart. Since connective tissue can serve for electrical conduction between cultured heart cells and since electrical properties of intestinal muscle permit transmission with low degrees of coupling, it is suggested that interstitial cells and fibrocytes may electrically couple longitudinal and circular muscle layers of cat intestine.

Beckham, Cassandra; Dimond, Richard; Greenlee, Theodore K.

doi: 10.1002/aja.1001500306pmid: 930858

D‐tubocurarine was injected into the air sac of 8‐day chick embryos to prevent movement of the digits of the hind limb. The embryos were paralyzed from the tenth to the eighteenth day, when the experiment was terminated. The immobilization of the flexor digitorum profundus tendons in the tarsus resulted in a loss of specialized structures around and on this tendon, as determined by light and electron microscopy. Specialized areas observed in the normal chick (synovial cavity, fibrocartilaginous area, and elastic vinculum) failed to form, as a result of the paralysis of the digit.

Gaare, John D.; Langman, Jan

doi: 10.1002/aja.1001500307pmid: 930859

The nasal region of 12‐day‐old mouse embryos was examined with the electron microscope to determine whether a surface coat and membrane specializations are involved in epithelial fusion between the medial and lateral nasal swellings. Ruthenium red was used to examine the distribution of the surface coat.

Gaare, John D.; Langman, Jan

doi: 10.1002/aja.1001500308pmid: 930860

The nasal fin is an epithelial seam that develops by fusion between the epithelial linings of the medial and lateral nasal swellings. Shortly after its formation the nasal fin regresses and is replaced by mesenchyme, with exception of its most posterior portion which remains as the bucconasal membrane. Since the regression of the nasal fin plays an important role in the formation of the upper lip and primary palate, the breakdown of the fin was examined with the electron microscope in 12‐day‐old mouse embryos.

Cavicchia, Juan Carlos; Dym, Martin

doi: 10.1002/aja.1001500309pmid: 412409

Techniques of quantitative stereology have been utilized to determine the relative volume occupied by the Sertoli cells and germ cells in two particular stages (I and VII) of the cycle of the seminiferous epithelium. Sertoli cell volume ranged from 24% in stage I of the cycle to 32% in stage VII. Early germ cells occupied 3.4% in stage I (spermatogonia) and 8.7% in stage VII (spermatogonia and preleptotene spermatocytes). Pachytene spermatocytes occupied 15% (stage I) and 24% (stage VII) of the total volume of the seminiferous epithelium. In stage I the two generations of spermatids comprised 58% of the total epithelium by volume, whereas in stage VII, after spermiation, the acrosome phase spermatids occupied 35% of the total seminiferous epithelial volume.