Cryptosporidiosis in three pigs.

Coccidia of the genus Cryptosporidium were found at necropsy in 3 pigs. The organisms were embedded in the microvillous border of crypt epithelial cells of the large intestine. Mild inflammation was associated with the infection but without clinical signs of enteritis.

Studies of spermatogenesis in the Hepaticae. II. Blepharoplast structure in the spermatid of Marchantia.

The blepharoplast in a young, developing spermatid of Marchantia polymorpha, is a composite structure consisting of two basal bodies and a subjacent narrow band of axonemal-type tubules that we have termed the "spline." For most of its length, the spline consists of six long parallel tubules that nearly encircle the cell. The spline anterior is asymmetrically widened for about 2 micro by shorter tubules of the same kind. The lateral displacement of three long, adjacent marginal tubules by three short intervening tubules at the spline tip produces a long narrow aperture. Distally, the aperture is closed by the convergence of the displaced tubules with another trio of long tubules. Together, these form the six-membered cell-encircling portion. The expanded spline anterior has, at this stage of development, the four-layered (Vierergruppe) structure, of which the aforementioned tubules constitute the uppermost layer. The lower three strata consist of diagonal fins, elongated chambers, and fine tubules, respectively. The two flagellar bases lie close above the spline tip-one slightly anterior to the other-and diverge unequally from the spline axis. A few triplets extend proximally from the basal bodies, but do not connect with the spline. The anterior basal body is longer than the posterior one.

Spermatogenesis in Polytrichum juniperinum : I. The origin of the apical body and the elongation of the nucleus.

Spermatogenesis in Polytrichum juniperrinum includes a series of precise and coordinated morphogenetic movements among the organelles of the androcyte. The basal bodies, the underlying microtubules, and the multilayered structure (MLS) are positioned as an integrated unit at the periphery of the cell, and the nucleus migrates into contact with them. The shape of the nucleus begins to change, with the formation of an anterior projection, or beak. The mitochondrial sheath that has coalesced on the plastid divides to form the apical body, and elongation of the nucleus begins. The posterior basal body and one microtubule undergo lateral displacement from the rear forward, as elongation of the nucleus and the microtubules continues. The mitochondrial mass that is now the apical body grows rearward along the side of the elongated nucleus, and the two groups of microtubules in the MLS rearrange themselves. The lower elements of the MLS also participate in the morphogenetic rearrangement. By the time the nucleus has elongated once around the cell and the apical body has begun it s rearward growth, the lower elements of the MLS are found only beneath the anterior basal body. Subsequently these layers disappear from this location also.

Spermatogenesis in Polytrichum juniperinum : II. The mature sperm.

In the mature sperm of Polytrichum, the nucleus contains only condensed chromatin. The apical body is as long as the posterior basal body, and the anterior basal body remains short. The microtubules that were part of the multilayered structure persist to form the filamentous appendage of the mature sperm. The cytoplasmic remnant contains the plastid and a few mitochondria that did not participate in the formation of the apical body.

Studies of spermatogenesis in the hepaticae. I. Ultrastructure of the vierergruppe in Marchantia.

Spermatids of the liverwort Marchantia polymorpha were shown by analysis of thin-sections to contain a four-layered organelle, the Vierergruppe, lying between the flagellar bases above and a subjacent mitochondrial body. The uppermost layer consists of parallel tubules structurally similar to those of the axoneme. Some of the tubules extend beyond the four-layered region to form a long ribbon-like appendage. The second layer consists of low, vertical, membranous fins connected by numerous short links to the tubules above. The third layer, limited above and below by two horizontal membranes, consists of vertical partitions, apparently continuous with the fins. The fourth and lowermost layer consists of narrow parallel tubules aligned beneath alternate partitions. The long axes of the lower three layers are parallel to each other and lie at an angle of 48 degrees to the tubule axis of the uppermost stratum. A graphic representation of a three-dimensional scale model interpreting organelle structure is given. The Vierergruppe supersedes Dreiergruppe interpretation in most if not all of the bryophytes studied to date.