Role of cortical microtubules in the orientation of cellulose microfibril deposition in higher-plant cells

Summary Cortical microtubules (MTs) have been implicated in the morphogenesis of plant cells by regulating the orientation of newly deposited cellulose microfibrils (CMFs). However, the role of MTs in oriented CMF deposition is still unclear. We have investigated the mechanism of CMF deposition with cultured tobacco protoplasts derived from taxol-treated BY-2 cells (taxol protoplasts). The BY-2 protoplasts regenerated patches of β-l,3-glucan (callose) and fibrils of β-l,4-glucan (cellulose). Taxol protoplasts possessed the same ordered MT arrays as material cells and regenerated CMFs with patterns almost coincidental with MTs. Electron microscopy revealed that, on the surface of cultured taxol protoplasts, each CMF bundle appeared to be deposited on each cortical MT. These results suggest that MTs may attach directly to the cellulose-synthesizing complexes, by some form of linkage, and regulate the movement of these complexes in higher-plant cells.     

The fine structure of mature spermatozoids of Chara corallina,with special reference to microtubules and scales

Summary New features recorded here for the first time include demonstration of the presence of a covering of tiny diamond shaped scales all over the body of the helical cell of the mature spermatozoids of Chara corallina Klein ex Willd. as well as a covering of slightly larger diamond shaped scales over the surfaces of the two flagella which has previously been seen by other authors in spermatozoids of both Chara and Nitella.The arrangement of microtubules in the anterior end of the spermatozoid, as a layer completely surrounding the anterior row of mitochondria resembles that of Chara fibrosa described by Pickett-Heaps 1968 and differs from that described for Nitella missouriensis by Turner 1968; these details are therefore perhaps phyletically significant.Other features such as the partial degeneration of the anteriorly placed flagellar bases are similar to those previously described for these two species although the distance between the bases and the point of emergence of the flagella from the body surface seems to differ somewhat from species to species.The investigation includes observations on the dehiscence of the antheridia and on the emergence of living cells from the spermatogenous filaments.The possible phyletic significance of some of these observations is discussed in a preliminary way.     

Early morphogenesis in the platyhelminthes with special reference to egg development and development of cestode larvae

Early development of fertilized eggs is reviewed for the main groups within the phylum Platyhelminthes (Turbellaria, Temnocephaloidea, Monogenea, Digenea, Cestodaria and Cestoda). The Turbellaria show two different patterns of embryological development consequent on whether yolk material is contained within the ovum membrane (endolecithal) or whether yolk is added to the outside of the ovum (ectolecithal). In the parasitic groups, those that are oviparous or ovoviviparous produce shelled eggs of the ectolecithal type and, in addition, there are viviparous forms in which egg development shows variations and the amount of yolk, where present, is reduced. In every case examined, however, cleavage is of the spiral type. Within the Cestoda, clear distinction is made between those groups (orders) of worms which are oviparous as compared to those which are viviparous. It is suggested that oviparity is more primitive (ancestral) than viviparity based on adult morphology and on the evidence of life-cycle studies.The continued, post-oncospheral development of cestodes is described as is the ultrastructure of various representative cercoid larval forms. These include: the procercoid of Pseudophyllidea and Haplobothrioidea; the cercoid of Tetraphyllidea; and, within the Cyclophyllidea, the cercoscolex of the Dilepididae, the cysticercoid of the Hymenolepidae, and the cysticercus of the Taeniidae. During post-oncospheral development, in every case examined the posterior part of the developing larva, the cercomer, can be characterized by a microvillar tegument (at least during early development) whereas the more anterior larval body itself, destined to develop in the definitive host, develops microtriches. Modifications to the cercomer, and its microvilli, in the later stages of post-oncospheral development, occur particularly in the more advanced Cyclophyllidea such as the Taeniidae and in some Hymenolepididae.     

Models for plant tissue development with cell division orientation regulated by preprophase bands of microtubules

Abstract. Interesting new ideas have recently been put forward concerning the regulation of cell division orientation in plants by preprophase bands of microtubules and by their sites of attachment on cell edges. These ideas can be shown to be related to cellular models of development with edge label control. It is the purpose of this paper to elaborate on this relationship and to point out applications of these models to morphogenesis in plant tissues with regular division sequences, particularly in the apical regions of roots of the fern Azolla pinnata.     

The problem of proprietary dyes,with special reference to alamar blue,a proprietary dye revealed

A short strip of adhesive transfer cellophane tape is applied to the face of the block to provide backing for the section during cutting and handling. The tape is sealed to the nuclear track plate with the section against the dry emulsion. After exposure the cellophane backing is removed by immersion in water, and the adhesive is dissolved from the section in unleaded gasoline. The section is hydrated and photographic and histological processing are carried out in the usual manner.