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Biomedical subjects

M A Sleigh

Publications and source records attributed to M A Sleigh.

At least 19 recordsLinked to original sources
PubMed1990

Ciliary adaptations for the propulsion of mucus.

The cilia that propel mucus are specialised for the function in their arrangement, length, some details of structure, beat pattern, beat cycle characteristics, metachronal coordination, local control of beat rate by response to mechanical stimulation and generalised control of beat rate by neurohormones. These features are matched to the properties of the visco-elastic mucus gel that is propelled at the ciliary tips above a low-viscosity periciliary layer whose depth must be regulated within defined limits.

Animals↗
PubMed1989

Adaptations of ciliary systems for the propulsion of water and mucus.

1. The characteristics of ciliary systems are determined by the dominance of viscous effects over inertial effects. 2. The velocity of water propulsion depends on ciliary length, beat frequency, pattern of beating, the arrangement of the cilia and their co-ordination. Beating cilia influence a layer of water only two or three cilium lengths deep, with maximal velocity near the ciliary tip. 3. Mucus is propelled by the tips of short cilia that penetrate the mucus; these cilia are closely spaced on epithelia, and achieve slow propulsion that is relatively independent of load and does not require strong ciliary co-ordination.

Animals↗
PubMed1988

Flagellar root maps allow speculative comparisons of root patterns and of their ontogeny.

A method of mapping the patterns of origin of flagellar roots around basal bodies in two-dimensional diagrams is suggested, making allowance for the varied orientations of members of a pair or quartet of basal bodies in a cell. The method is used to compare flagellar root patterns in a wide range of protistan groups, and appears to demonstrate similarities in many areas. Comparison of such patterns in three published examples shows that during the ontogeny of a basal body it may display first one root pattern and then another, so that the root array of a given basal body is not fixed but changes with the position and role of that basal body in the cell.

Animals↗
PubMed1988

The propulsion of mucus by cilia.

The presence of cilia on epithelia of the respiratory tract was reported more than 150 yr ago, and the two-layer model of mucus transport was put forward more than 50 yr ago. However, it is only in the last 10 yr or so that the motion of mucus-propelling cilia of the mammalian respiratory system has been adequately described, and fluid dynamic studies have developed far enough to allow descriptions of the mechanisms by which ciliary movement is coupled to mucus transport. In this review, scientific developments on the study of cilia and mucus, and interactions between them, are drawn together to further understanding of mucociliary clearance mechanisms of the respiratory tract. The study of the cilia incorporates a discussion of the internal mechanics and biochemistry of the ciliary axoneme, the physical principles of the beat pattern, and the (weak) metachronal coordination of cilia in the lung. Mucus rheology plays a central role in mucociliary transport with the rheologic properties of the mucus determining the effective functioning of this clearance mechanism. Theoretical models provide information on the mechanical principles of the beat pattern as well as providing reliable estimates of the transport rates. Although airflow is not thought to contribute to mucus transport in the normal state, high frequency ventilation and coughing may make significant contributions.

Animals↗
PubMed1984

The effects of serum immunoglobulins on the metachronal coordination of the lateral cilia of Mytilus edulis.

Human IgM and a bovine, IgM-enriched serum fraction isolated from normal adult serum at concentrations of 0.25-1 mg/ml protein induced a pronounced increase in the metachronal wavelength of the lateral (L) cilia of the sea mussel Mytilus edulis without altering their beat frequency. This change in activity was indistinguishable from that induced by 50% adult human or bovine serum. At protein concentrations ranging from 1-9 mg/ml, human IgG or a bovine, IgG-enriched serum fraction had no or little effect on the activity of the L cilia. Similarly, neither monomeric (8S) human IgM (0.25 mg/ml) nor monospecific pentameric IgM (1 mg/ml) isolated from Waldenström's macroglobulinemia patients altered the metachrony of the L cilia. Indirect immunofluorescence demonstrated that both bovine and human IgM became attached almost exclusively to the L cilia, while very little bovine or human IgG was found to associate with these cilia. The results of this study suggest that serum IgM specifically binds to the L cilia of Mytilus in an antigen-antibody manner and agglutinates adjacent cilia into blocks or bundles, thereby increasing the coupling between cilia. As a result, the wavelength of the metachronal coordination is increased. The origin of these ciliary antibodies and their significance to ciliary bioassays used to monitor serum for the detection of cystic fibrosis are discussed.

Animals↗
PubMed1983

Kartagener's syndrome, ciliary defects and ciliary function.

The several genetically-determined structural defects of cilia that cause ineffective mucociliary clearance in Kartagener's syndrome and related diseases (for which the group name Primary Ciliary Dyskinesia is thought most appropriate) are compared with structural defects of flagella of mutant Chlamydomonas, about which biochemical information is also available. This comparison suggests that the effective activity of several or many genes may be essential for formation of each of the major components of the ciliary axoneme, and that Primary Ciliary Dyskinesia may result if a patient is homozygous for ineffective genes at any one of these gene loci. However, the mutants often appear to be "leaky", with incomplete effects; in addition, structural abnormalities of human cilia are relatively common in apparently normal individuals. The relationship of axonemal defects to disorientation of ciliary bases is questioned and the possibility is raised that such disorientation may result from morphogenetic disturbances through infection rather than from genetic origins.

Chlamydomonas↗
PubMed1983

Ciliary function in transport of mucus.

Mucus is propelled by short cilia which rest during each beat cycle. Cilia move from rest by bending sideways and backwards through a recovery stroke in which they keep near the cell surface. This is followed by an effective stroke, in a plane nearly perpendicular to the cell surface, which ends with the cilium bent over in its rest position and with its tip pointing in the direction of propulsion. The cilium moves in a layer of periciliary fluid whose depth is a little less than the ciliary length, so that the overlying mucus is only penetrated by the ciliary tips in the effective stroke. The thickness of the periciliary layer is critical for effective propulsion of mucus. The cilia are coordinated by visco-mechanical interaction between the moving units to produce short oblique metachronal waves which pass across a few ciliated cells before dying away. Many small areas of independently coordinated activity collaborate to propel the overlying mucus. The activity of the cilia can respond to the load of mucus and control of ciliary rate may be exerted indirectly by varying the load rather than by any direct neural mechanism.

Animals↗
PubMed1982

How are different ciliary beat patterns produced?

In this paper, the generation of different patterns of beat is discussed in terms of the internal mechanism of the cilia. A simple classification is proposed for the wide variety of patterns of planar beating. Ctenophore comb plates can show four types of movement: arrest, reverse beating, flagellar beating and forward beating. Other types of cilia show several or all of these beat patterns. Following stimulation of the organism these different beat patterns occur in a definite sequence which is the same in all cases. There is some evidence in each example that change in beating activity from the normal pattern towards the arrest or reversal response is associated with an increase in intraciliary Ca2+ concentration, and it is suggested that the sequence normal ciliary beat leads to symmetrical flagellar beat leads to reverse ciliary beat leads to active arrest represents the response of the axoneme mechanism to progressively increasing levels of intraciliary Ca2+ concentration, different patterns of beat resulting from different patterns of activation of the dynein arms within the axoneme.

Animals↗
PubMed1979

Freeze substitution for preservation of ciliated surfaces for scanning electron microscopy.

A technique is described for arresting rapid movement of living cells and preserving their fine surface structures for scanning electron microscopy. Rapid freezing is recommended as the method of immobilization and freeze substitution has been employed to fix and dehydrate the specimens; this technique is more reliable than osmium fixation, both in terms of obtaining a much higher proportion of good results and in the improved preservation of detail. Various techniques of substitution have been investigated for best preservation, and the roles of the constituents of the substitution mixture have been discussed.

Alcohols↗
PubMed1976

Behavior of the contractile vacuole of Tetrahymena pyriformis W: a redescription with comments on the terminology.

The behavior of the contractile vacuole of Tetrahymena pyriformis W has been recorded and analyzed quantitatively by cinephotography. The vacuole fills in a stepwise fashion by the confluence of ampullae which appear regularly at the beginning of systole and whose membranes are continuous with that of the contractile vacuole throughout the cycle. The vacuole may subsequently fill slowly by a means not discernible by light microscopy. The vacuole rounds up at the beginning of systole and shortly thereafter the ampullae reappear around the perimeter of the vacuole. They are expanded by fluid forced into them from the vacuole. Round-up and the mode of growth of the ampullae indicate that the contractile vacuole is truly contractile. Expulsion occurs soon after the appearance of the ampullae and terminates the cycle. Contraction is initiated at regular intervals by a timing mechanism which is independent of the size of the vacuole. Suitable terminology to describe the structure and behavior of the contractile vacuole is discussed.

Animals↗