Beat Direction Research Articles

Heat Flux Distribution Near a Crevasse

AbstractPreviously reported experimental temperature data were used to compute the two components of the heat flux vector in the ice body adjacent to a crevasse in a glacier of the ice sheet of northern Greenland. Graphical differentiation techniques were employed. The computed components were used to synthesize values of the beat flux vector, including magnitude and direction. Improved accuracy was achieved over the previously reported technique of sketching heat flow lines orthogonal to the isotherms.

The relationship between the fine structure and direction of beat in gill cilia of a lamellibranch mollusc.

This paper describes the fine structure and its relationship to the direction of beat in four types of cilia on the gill of the fresh-water mussel Anodonta cataracta. The cilia contain nine outer, nine secondary, and two central fibers, such as have been described previously in other material. Each outer fiber is a doublet with one subfiber bearing arms. One particular pair of outer fibers (numbers 5 and 6) are joined together by a bridge. The two central fibers are enclosed by a central sheath; also present in this region is a single, small mid-fiber. The different groups of fibers are connected together by radial links that extend from the outer to the secondary fibers, and from the secondary fibers to the central sheath. The basal body consists of a cylinder of nine triplet fibers. Projecting from it on one side is a dense conical structure called the basal foot. The cylinder of outer fibers continues from the basal body into the cilium, passing through a complex transitional region in which five distinct changes of structure occur at different levels. There are two sets of fibers associated with the basal bodies: a pair of striated rootlets that extends from each basal body down into the cell, and a system of fine tubular fibers that runs parallel to the cell surface. The relationship between fine structure and direction of beat is the same in all four types of cilia examined. The plane of beat is perpendicular to the plane of the central fibers, with the effective stroke toward the bridge between outer fibers 5 and 6, and toward the foot on the basal body.

The fine structure of the cilia from ctenophore swimming-plates.

The ctenophore swimming-plate has been examined with the electron microscope. It has been recognized as an association of long cilia in tight hexagonal packing. One of the directions of the hexagonal packing is parallel to the long edge of the swimming-plate and is perpendicular to the direction of the ciliary beat. All the cilia in the swimming-plate are identically oriented. The effective beat in the movement of the swimming-plate is directed towards the aboral pole of the animal, and this is also the side of the unpaired peripheral filament in all the cilia. The direction of the ciliary beat is fixed in relation to the position of the filaments of the cilia. The swimming-plate cilium differs from other types of cilia and flagella in having a filament arrangement that can be described as 9 + 3 as opposed to the conventional 9 + 2 pattern. The central filaments appear in a group of two "tubular" filaments and an associated compact filament. The compact filament might have a supporting function. It has been called "midfilament." Two of the peripheral nine filaments (Fig. 1, Nos. 3 and 8) are joined to the ciliary membrane by means of slender lamellae, which divide the cilium into two unequal compartments. These lamellae have been called "compartmenting lamellae." Some observations of the arrangement of the compartmenting lamelae indicate that they function by cementing the cilia together in lateral rows. The cilia of the rows meet at a short distance from each other, leaving a gap of 30 A only. The meeting points are close to the termini of the compartmenting ridges. An electron-dense substance is sometimes seen bridging the gap. Some irregularities are noted with regard to the arrangement of the compartmenting lamellae particularly at the peripheral rows of cilia. In many cilia in these rows there are small vesicles beneath the ciliary membrane.

The Form of Beat in Cilia of Stentor and Opalina

ABSTRACT The patterns of beat in cilia of Stentor and Opalina are described. A fibrillar contraction mechanism is suggested to explain the beating of these cilia and of flagella. The diverse forms of beat are thought to result from differences in the relative timing of parts of the contraction process in different organelles. In both types of ciliary beat the effective and recovery phases are in progress simultaneously and are inseparable parts of one continuous contraction process. The average rate of propagation of the contraction wave in Stentor cilia was 844 μ/sec., which is comparable with the rate found in echinoderm sperm tails. In Opalina cilia the rate was much slower at between 20 and 100 μ/sec. The peristomial cilia of Stentor always beat in the same direction, but Opalina cilia may show co-ordinated beat in any direction, and the form of beat appears the same whatever the direction of beat.

CILIARY STREAMING THROUGH THE LARYNX AND TRACHEA: Relation to Direction of Ciliary Beat and Significance in Sites of Respiratory Disease

CILIARY STREAMING THROUGH THE LARYNX AND TRACHEA: Relation to Direction of Ciliary Beat and Significance in Sites of Respiratory Disease

Aspects of ciliary fine structure in Euplotes patella.

1. The functional unity of cirri and membranelles can result structurally only from extensions of the ciliary membrane. 2. The pellicle is composed of an outer pellicular membrane and an inner cytoplasmic membrane. 3. The ciliary rootlets are composed of numerous filaments 120 A in diameter with central areas of low density. They have no periodic structure. 4. The ciliary membrane is a double-layered structure continuous with the pellicular membrane. The cilia show the typical arrangement of nine double, peripheral and two single, central fibrils. All fibrils pass into the basal region, the peripheral ones joining with the rootlet filaments, while the central fibrils from the extreme proximal position of the basal region turn back toward the pellicle and appear to unite just beneath the cytoplasmic membrane. 5. The cilia (300 mmicro diameter) taper at their tips to a diameter at least as small as 50 mmicro. At a diameter of about 150 mmicro, the fibrils begin to show a reduction in number. 6. The central ciliary fibrils may determine the possible directions of ciliary beat. These fibrils show an intrafibrillar structure in their basal portion, which involves regularly spaced 40 A granules. 7. These observations on Euplotes, together with the other evidence cited, are consistent with the hypothesis that ciliary motion is produced by the contraction of the peripheral fibrils, while the central fibrils perhaps determine the plane in which the cilia can bend.

Relations between Metachronism and the direction of ciliary beat in metazoa

ABSTRACT In various ciliated epithelia one can distinguish either symplectic, antiplectic, dexio-plectic, or laeoplectic metachronal waves, according to whether the effective beat of their cilia is with, against, to the right of, or to the left of, the direction of movement of the waves. In a given epithelium the relation between the direction of the waves and the direction of beat is constant. Symplectic waves are probably associated with the transport of large particles, or viscous masses of mucus; antiplectic and diaplectic waves are better suited for creating water currents. It is unusual to find both dexioplectic and laeoplectic waves in the same animal; indeed, it is the rule for only one of these two types of metachronism to occur throughout a given systematic group. Dexioplectic waves are found in Protochordata, primitive Spiralia, the velum of Eulamellibranchiata, Phoronidea, Brachiopoda, Bdelloidea, and Melicertida; laeoplectic waves are found in Chaetopterus, Mollusca generally, Bryozoa, and Ploima. The incidence of dexioplectic and laeoplectic meta-chronism is not influenced by morphological reversals of symmetry such as the situs inversus. The relation between the direction of beat and the direction of the waves is therefore probably determined by cytological or stereochemical factors, rather than by gross morphology.

A New Method of Ciliary Feeding in the Brachiopod Neothyris lenticularis

THE Pygocaulian Brachiopod Neothyris lenticularis possesses sets of ciliated filaments similar to those in other invertebrate filter feeders. Studies on this form, however, have shown that the method of feeding is very different from that in other ciliary feeders—Lamellibranchs1, certain sedentary Gastropods2, Cryptocephalous Polychaetes3, Tunicates and Amphioxus4, Entoproct and Ectoproct Polyzoa5,6 and Crania7. There are two fundamental points of difference, namely, the function of the filaments and the direction of beat of the cilia on the filaments.

Effect of Some Chemicals, Which Affect Smooth Muscle Contraction, on Ciliary Activity in Paramecium.

Mast and Nadler, Merton, Oliphant and others have shown that monovalent cation salts and hydrates induce reversal in the direction of the effective beat of the cilia in protozoa while, with few exceptions, bi- and tri-valent cation salts and hydrates do not. Similar observations have been made regarding ciliary reversal in the metazoa, and the reproductive cells of plants and animals have been observed to swim backward. Alverdes, Worley and others have also shown that in fragments of ciliated protozoa the cilia continue to beat as long as they are connected with a fragment of cytoplasm. Such ciliated fragments have also been observed to reverse direction of ciliary beat in response to environmental change and this suggests that cilia here are automatic in their activity and that alterations in ciliary behavior are of an extraneous nature. Furthermore it is now generally agreed that the fundamental phenomena of protoplasmic contractility are essentially alike for pseudo-podial movement, ciliary activity and muscular contraction, and that a theory which will adequately explain one will doubtless be applicable to the others.6-8 However the demonstration of similarity between various forms of cellular movement is by no means complete. From these observations and assumptions it would be expected that substances which profoundly affect cellular movement in populations of smooth muscle cells would also profoundly affect ciliary activity, possibly inducing ciliary reversal. It is the object of this investigation to explore the possibility of such a similarity in behavior of ciliated and smooth muscle cells in response to chemical agents in the environment, with a view to contributing to the analysis of chemical and physical factors involved in protoplasmic contractility.

Ultraviolet Point Radiation in the Production of Arrythmias in the Heart of the Chick Embryo.

By means of apparatus previously described,1 a point source of radiation could be directed on the desired spot on the developing embryonic heart and its effect on the rhythm noted. Studies were made on embryos varying in age from 2 to 20 days, and the following results obtained: Short exposures of the sinus region of the heart produced an increase in rate of beat within 30 seconds after the exposure was begun. A long-continued exposure slowed the rate. Exposure on the ventral aspect of either auricle (at a point of visible condensation of tissue) also produced a marked increase. Exposure of the ventricle did not change the rate of beat except when the point of the quartz rod was placed on the interventricular septum at the base of the auricles. A slight increase was then obtained in hearts whose rate had already been slowed.Also, in young hearts (2 to 6 days old), it was possible to obtain complete reversal of the direction of beat by a preliminary slowing brought about by lowering the temperature, and th...