Microscopical observations on the excretory organs of the hydrothermal mussel Bathymodiolus thermophilus (Mollusca: Bivalvia)

The pericardial gland of the deep-sea hydrothermal mussel Bathymodiolus thermophilus (Mollusca: Bivalvia: Mytilidae) differs from other mytilids by (1) a narrow lumen and (2) conspicuous polyhedral inclusion bodies in large cytoplasmic vacuoles of the epithelial cells. These inclusions do not contain metals as revealed by microanalysis but are possibly made of proteins. The cells of this gland exhibit a fenestrated basal border which indicates a site of haemolymph ultrafiltration. The kidney is histologically comparable to that of the coastal mussel Mytilus edulis.

Intracellular calcium and the regulation of sodium transport in the frog skin

Exposure of frog skins to Na-free solutions on the basal border causes a reduction in transepithelial Na transport. Since Na-free solutions produce an increase in cell Ca concentration in some cell types, we have explored whether such increase plays a rôle in their inhibitory effects on transepithelial transport. Measurements of 45 Ca uptake in isolated epithelia showed that Na-free solutions caused a threefold stimulation of Ca uptake; nearly all the increased uptake occurred through the basal border. The reduction in transepithelial Na transport caused by Na-free solutions was absent when Ca was also eliminated from the basal solution. These findings suggest that the reduction in transepithelial Na-free solutions is caused by increased cytoplasmic calcium levels. We also found that during the action of metabolic inhibitors, Ca efflux from the epithelium was increased markedly. Since such as increase in efflux is probably due to increased (Ca) in the cytoplasm, we suggest that the reduced epithelial Na permeability observed during metabolic inhibition may be due to increased cytoplasmic calcium.

Thick, layered peridotite–gabbro lava flows in Munro Township, Ontario

Two unusually thick (120 m) lava flows in Munro Township, Ontario, are differentiated from peridotite at the base to gabbro near the top. One flow is komatiitic and contains the following units (from top to bottom): ultramafic flow-top breccia (19.5% MgO); olivine and pyroxene spinifex-textured rocks (17–10% MgO); gabbro (7% MgO); pyroxene cumulates (10–25% MgO); olivine cumulates (32–35% MgO); and a basal border zone. The composition of the lava at the time of eruption is believed to be represented by the ultramafic flow-top breccia. Following eruption, this lava differentiated to produce ultramafic cumulate rocks, and liquid of quartz-normative basaltic composition that solidified as gabbro.The other flow is tholeiitic and has a picritic hyaloclastite flow top (14% MgO) underlain successively by an aphanitic pyroxenite zone (but no spinifex texture), a gabbro zone, a thick clinopyroxene-rich cumulate unit, and a thin basal veneer of cumulate olivine.

Ultrastructural Changes in the Chlamydia-Infected Ileal Mucosa of Newborn Calves

Ultrastructural changes induced by chlamydial infection of mucosal cells of the ileum of newborn calves after oral inoculation were investigated. Depending on the stage of chlamydial development, the organelles of all infected cells became damaged. The damage was degenerative and included vesiculation of microvilli and swelling of the terminal web of absorptive epithelial cells. The mitochondria were swollen and had fragmented cristae. The endoplasmie reticulum was dilated and vesiculated, and infected cells gradually lost their ribosomes. The lateral junctional complex between infected cells became occasionally dislocated and fragmented. The basal lamina was thrown into folds, became discontinuous and separated from the basal border of the epithelial cells. The nuclei of infected cells were affected last, lost their chromatin pattern, and ultimately became pyknotic.

V. On the Megatherium (Megatherium americanum, cuvier and blumenbach) . Part IV. —Bones of the anterior extremities

The bones of the limbs of the Megatherium are not less fraught with interest to the comparative Anatomist and Physiologist, than are those of the trunk and head, by reason their peculiar proportions and configurations, and more especially as the unguiculate type on which they are constructed is exemplified in a quadruped of such enormous bulk. The anterior extremities (Plate XVIII.) exceed the posterior ones in length: in their bony structure they include a complete clavicle (58) with the scapula (51), a humerus (53), an antibrachium, consisting of fully developed and reciprocally rotating radius (55) and ulna (54), carpus, metacarpus, and four digits; they manifest, in short, all the main perfections of brachial structure, save the opposable thumb, observable in the mammalian ass. These perfections, moreover, are associated with proportions and processes indicative of enormous strength, and bespeak a limb fitted not only to take its full share in e support of the body, but to be employed on operations in which unusual resistance id manifestly to be overcome. In no respect, perhaps, does the Megatherium more strikingly differ in its osseous structure from the existing quadrupeds of corresponding bulk, than in the bony fulcra of the anterior extremity. Scapula . —The scapula (Plate XVIII. 51, and Plate XIX. figs. 1 and 2) is a vast expanse of bone, with a double spinous process; the normal one expanding into a large acromion, which is continued into, and is confluent with, the coracoid process. The scapula usually presents an inequilateral triangular form (Plate XIX. fig. 1), of which e acromion ( k ) is the apex. The upper border ( b, c ) is the shortest; but, in one specimen, owing to the greater development of the basal border, as indicated by the dotted outline in Plate XIX., the upper border appeared to begin at the part of the base marked a , and to form a low angle, as if continued about one-fourth of the distance from the base parallel with the lower border, whilst the rest of the costa inclines downward towards the coracoid ( c ), with a slight concave outline. The upper border increases in thickness as it passes into the origin of the coracoid. The base of the scapula, from the point a , is straight as far as the origin of the spine, a' ; it then bends, with a convex curve, and increases in thickness to the inferior angle of the scapula ( d ), close to which commences the second or lower spine. The inferior costa of the scapula extends forward, straight and parallel with the lower spine, for some way, and then is lost upon the inner surface, the lower spine itself appearing, at e , to form the inferior costa for the rest its course to the glenoid cavity ( g ).