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Biomedical subjects

M L Mackenzie

Publications and source records attributed to M L Mackenzie.

7 recordsLinked to original sources
PubMed1998

Assessing the changing diet of indigenous peoples.

Because a dietary transition is occurring among indigenous populations from traditional foods to more market (store-bought) foods, there are concerns about a rise in diet-related chronic disease. More research into dietary intakes of indigenous peoples is needed. When the use of longitudinal studies is not possible, the use of cross-sectional data to characterize the process of dietary change appears to be an appropriate way to assess change during rapid transition.

Adult↗
PubMed1989

The vasa nervorum: microcorrosion casts for scanning electron microscopy.

Studies on the vasa nervorum have a long history, not least because of their beneficial application in surgical practice and in understanding the pathogenesis of some neuropathies. In the present study a method is described for the preparation of microcorrosion casts of the vasa nervorum suitable for examination by scanning electron microscopy. The results confirm the findings of earlier investigations but also demonstrate the advantages of an immediate three-dimensional representation of the vascular architecture together with the additional magnification and resolving power of electron microscopy.

Animals↗
PubMed1985

Filipin-sterol complexes at nodes of Ranvier.

Using the filipin-sterol technique, regional heterogeneity in the axonal and Schwann cell plasma membranes was investigated at the node of Ranvier and paranodes. Filipin-sterol complexes were abundant at the nodal axolemma but infrequent throughout the paranodal axolemma. The paranodal Schwann cell plasma membrane was rich in complexes which extended over the nodal Schwann cell microvilli. There were no regional differences in filipin labelling of the nodal-paranodal Schwann cell plasma membrane in relation to features such as paranodal cytoplasmic columns or mesaxonal furrows. However, the paranodes of adjacent Schwann cells were sometimes markedly different from each other in the amount of filipin labelling. The extent to which filipin labelling is indicative of cholesterol membrane content is discussed and the findings are related to current concepts of distribution, mobility and interaction of protein and lipid in biomembranes, with particular reference to the nodal axolemma.

Animals↗
PubMed1984

Myelinated nerve fibres and the fate of lanthanum tracer: an in vivo study.

The permeability of the marginal tight junctional system of myelin was tested in the rat employing the electron-dense tracer lanthanum nitrate. Lanthanum was either included in the fixative used for vascular perfusion (at a concentration of 20 mM) or was microinjected in vivo into the sural or tibial nerve (5, 10 and 20 mM). After 5-60 minutes, the microinjected nerves were fixed either by immersion or vascular perfusion. Lanthanum tracer was present in the intraperiod line gap of myelin, irrespective of the mode of application of the tracer, the method of fixation or the time of exposure to lanthanum. However, the tracer was present more extensively when included in the fixative compared with in vivo microinjection. Internodally, lanthanum was usually restricted to the inner, or more commonly, the outer lamellae of larger fibres, while all lamellae were usually penetrated by tracer in smaller fibres. Paranodally, compact myelin was more extensively penetrated. The periaxonal space (between axon and Schwann cell) was readily accessible to tracer. It is concluded that the marginal tight junctional system of myelin is apparently of the 'leaky' type and is permeable to ions. The findings have implications for the electrophysiology and pathophysiology of the myelinated nerve fibre.

Animals↗
PubMed1980

The effect of blood flow on the surface morphology of the human endothelium.

The endothelial lining from the aortae of three 17 week human fetuses was examined by scanning electron microscopy. Orientation of the endothelial cells, particularly in the region above the aortic valve, was related to known flow patterns. Endothelial morphology showed regional variation noticeably at the mouths of arteries and at the aortic bifurcation. The possibility that this morphological change may be a hitherto unrecognised risk factor related to the site of atheromatous deposition is discussed.

Aorta↗
PubMedDate not supplied

Some scanning electron microscopic features of human cervical epithelium in cell culture.

Human cervical epithelial cells, growing out in confluent monolayers from small explants, develop cytoplasmic extensions from the margins of the growth, extending out and terminating on the glass substrate. The marginal fibrils are particularly frequent on the edges of cellular lamellipodia, protruding in advance of the growing edges. Marginal cells with microvilli tend to have more marginal fibrils on their leading edges than smooth more differentiated cells, and occasionally there is continuity between microvilli and marginal fibrils. Where there is cellular overlap, marginal fibrils extending over the surface of another cell can be seen; where these is an intercellular cleft, cytoplasmic bridges have the same appearance as marginal fibrils. Colchicine (10-6 M) did not affect marginal fibril formation.

Cells, Cultured↗