American Journal of Anatomy

doi: 10.1002/aja.1001380101pmid: N/A

Grant, Philip G.

doi: 10.1002/aja.1001380102pmid: 4200389

Reinterpretation of existing data and introduction of new evidence appear to indicate that this controversial muscle might better be treated as two muscles. Anatomically the lateral pterygoid in man and in the rhesus macaque has two distinct heads, superior and inferior. Biomechanically, the two heads posses different properties: the superior head has a closing moment (or perhaps no moment) while the inferior head has an opening moment. The findings are similar in the two species. Electromyographically the two heads show different activity patterns: the superior head is active during various jaw‐closing movements only, while the inferior head is active during jaw‐opening and protrusion only. Functionally, therefore, the lateral pterygoid of man and rhesus macaque appears to be two muscles.

Etherton, John E.; M. Conning, David; Corrin, Bryan

doi: 10.1002/aja.1001380103pmid: 4582356

The Clara cell of the mouse terminal bronchiole has been examined by high resolution phase contrast and electron microscopy, and the secretory route of surfactant in the mouse lung has been investigated using both light and electron microscopical autoradiography of a surfactant precursor (palmitic acid). Serial sections of terminal bronchioles examined by phase contrast microscopy demonstrated the appearances of apocrine secretion of amorphous droplets by Clara cells. Electron microscopy showed that the non‐decapitating supranclear region of Clara cells contained numerous rounded mitochondria with scanty achrestic cristae, whilst the apical portion was rich in smooth tubular membranes. Autoradiographical labeling of bronchiolar Clara cells exceeded that of all other cell types within three minutes of administration of the radioactive precursor, with location primarily over the endoplasmic reticulum. Subsequently there was heavy labeling of the bronchiolar lining layer. An hour later, silver grains were most numerous over the lamellated bodies of type II cells. It is suggested that palmitic acid is synthesized in the specialized mitochondria of the non‐secretory region of the Clara cell and is incorporated into dipalmitoyl lecithin in the membranous apex. Subsequent secretion, possibly by the apocrine mechanism, provides a surface‐active bronchiolar lining layer.

S. Forbes, M.; A. Zaccaria, R.; N. Dent, J.

doi: 10.1002/aja.1001380104pmid: 4741500

The cytology of pigment‐bearing cells is followed in the integument of the red‐spotted newt, Notophthalmus viridescens viridescens Rafinesque, with observations beginning in the late embryo and continuing through to the adult. Dermal melanophores appear in late tailbud stages, and dermal xanthophores differentiate prior to hatching. In young larvae, both become widely and evenly distributed in the dorsal skin, but in older larvae a pattern develops so that melanophores are absent from certain circumscribed lateral regions designated as melanophore voids. Iridophores differentiate and accumulate among the xanthophores which have remained in the voids. Those xanthophores then are transformed into proerythrophores; that is, their form is altered from stellate to punctate, their nuclei change from fusiform to ovoid, and their pterinosomes are largely replaced by lipid droplets. In some of the voids, the proerythrophores migrate into the epidermis to become the erythrophores of the red spots. The remaining voids cease to exist when their proerythrophores disappear and are replaced by dermal melanophores. At the same time, some dermal melanophores accumulate to form dorsal black spots, and a morphologically different type of melanophore differentiates within the epidermis. In the interspot regions of the eft, xanthophores hypertrophy and pack the dermis, giving an orange color to the skin. In the interspot regions of the adult newt, xanthophores with fewer organelles produce a yellow color on the ventral surface, and, in combination with melanophores and iridophores, produce a greenish color in the dorsum.

Jean Adamo, Norma; A. Daigneault, Ernest

doi: 10.1002/aja.1001380105pmid: 4741501

Electron microscopic study of the cat's spiral ganglia reveals that neuronal cytoplasmic extensions evaginate into the inner Schwann cell lamellae; some may become surrounded by the ensheathing Schwann cell. Inner lamellae of ensheathing Schwann cells penetrate the neuron and invest small portions of neuronal cytoplasm. Membrane‐bound neuronal regions, completely or partially bare of Schwann cell ensheathment, also are observed within neurons or adjacent to the neuronal plasmalemma. Some of these isolated neuronal regions might represent cytoplasmic extensions of the same or another neuron. Speculations are made as to the mechanism by which the observed relationships are formed.

Warshawsky, H.; Haddad, A.; P. Gonçalves, R.; Valeri, V.; L. De Lucca, F.

doi: 10.1002/aja.1001380106pmid: 4741502

The South American rattlesnake venom gland is made up of secretory tubules lined by a simple columnar epithelium containing horizontal cells, mitochondria‐rich cells, and the principal cell type, the columnar secretory cells. This cell has a round basal nucleus and abundant rough endoplasmic reticulum, the cisternae of which are variably distended with flocculent material containing many dense intracisternal granules. The supranuclear Golgi apparatus is spherical, with stacks of flattened saccules at the periphery and large vacuoles containing masses of dense material, and other dense granules in the center. Similar but smaller granules are present at the apex where they fuse with the microvillus‐covered apical membrane and release their content into the lumen. Protein synthesis was studied in snakes injected with 3H‐tyrosine and sacrificed at several times after injection. Radioautographs showed reactions at one half and one hour over the ribosomes and membranes of the rough endoplasmic reticulum. At two hours the immature face of the Golgi apparatus was labeled. At four hours Golgi saccules and vacuoles with dense masses (secretory granules) were labeled, and at eight hours the dense masses within the secretory granules were heavily labeled both in the Golgi region and in the apex near the lumen. Labeled material was found in the lumen at two days. Intracisternal granules were first labeled at eight hours, and by two days reactions remained only over the flocculent content and intracisternal granules of the rough endoplasmic reticulum. Thus, venom protein was synthesized on the rough endoplasmic reticulum, migrated through the Golgi apparatus and accumulated in the dense masses of the secretory granules, which moved to the apex and were extruded. The labeling of intracisternal granules at eight hours and two days after injection indicated a storage nature for these granules.

L. Zimny, Marilyn

doi: 10.1002/aja.1001380107pmid: 4270209

The glomerular basement membrane in the kidney of a hibernating 13‐lined ground squirrel, when compared with that of a non‐hibernating animal, stains positively with ruthenium red indicating the presence of acid mucopolysaccharide. This increased quantity of anionic material accompanying hibernation may be responsible for maintaining water and electrolyte balance by acting as a resin for the exchange of cations between the capillary and urinary spaces, attracting water and concentrating protein.

R. Shear, Charles; Keith O'Steen, W.; V. Anderson, Kenneth

doi: 10.1002/aja.1001380108pmid: 4741497

Retinas of albino rats exposed to continuous, low intensity fluorescent light for periods of 6, 12, and 18 hr display fine structural changes in both pigment epithelial cells and in the outer segments of the photoreceptor cells. Adjacent pigment epithelial cells showed wide intercellular spacing (600 to 36,000 A) and retraction of the villous processes. As the rats were exposed to increasingly longer photoperiods, the lamellated discs, which are flattened in dark‐adapted retinas, became progressively more tubular.

O. Simpson, Leslie

doi: 10.1002/aja.1001380109pmid: 4741498

Multiple regression analysis of the relationships of thymus weight to age and body weight, suggests that thymic growth patterns are widely variable and possibly are strain characteristics.

Duncan, Donald; Morales, Ricardo

doi: 10.1002/aja.1001380110pmid: 4741499

A search for the cells of origin of synaptic vesicles with electron‐opaque cores and located in the substantia gelatinosa was attempted by subjecting cats to transection of dorsal roots and double hemisection in the upper lumbar region. The hemisections were accompanied by interruption of the dorsal rootlets to the affected segment. The cats were perfused with buffered aldehydes and processed for electron microscopy 55–71 days after the operations. Comparison of intact and operated sides of the rhizotomized cats revealed no discernible differences in numbers and location of the granulated vesicles associated with the substantia gelatinosa. In cats with double hemi‐section plus rhizotomy the distribution of the granules was the same on the normal and operated sides but the numbers appeared to be reduced especially close to the surgical incisions. Dark‐core vesicles were situated in association with the Golgi apparatus of substantia gelatinosa neurons, in dendrites, in small axons and in synaptic sacs in all material studied. It was concluded that most of the granulated vesicles located in the substantia gelatinosa are produced by small neurons in the immediate vicinity of their axon terminals.