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Biomedical subjects

M Cusack

Publications and source records attributed to M Cusack.

12 recordsLinked to original sources
PubMed2003

Magnesium and phosphorus distribution in the avian eggshell.

Magnesium and phosphorus are major inorganic constituents of the avian eggshell. The Mg/Ca ratio has been used as a palaeothermometer in a range of calcite biominerals. Eggshells provide the opportunity to examine the Mg/Ca ratio of a calcite biomineral produced in a constant temperature environment. Mg distribution is not constant throughout the shell, decreasing from nucleation until after fusion of the mammillary caps and then increasing to termination. This indicates that temperature of deposition is not the only factor controlling the Mg content of this biomineral system. There is a greater increase in magnesium concentration in the outer region of eggshells from older birds. The variation in magnesium concentration does not appear to correlate with organic content. Phosphorus occurs in the outer quarter of the eggshell and rises to termination and is therefore not confined to cuticular vesicles.

Animals↗
PubMed2001

The nature of siliceous mosaics forming the first shell of the brachiopod Discinisca.

The juvenile shell of the brachiopod Discinisca consists of a mosaic of micrometer-sized siliceous tablets embedded in a chitinous substrate. The first-formed tablets are secreted on glycocalyx by a newly differentiated collective of outer epithelial cells. They are mainly rhombic but may also be ellipsoidal, discoidal, or deformed and sporadically overlap one another. On the surrounding juvenile shell, secreted by an incipient outer mantle lobe, the tablets are nearly all perfect rhombic plates in rhombic arrays. Their constant size, arrangement, and centripetal crystallization suggest intracellular assembly. The tablets, which are normally bilamellar, consist of discrete aggregates of crystalline spherules of silica in rhombic arrays within an organic matrix of fibrous protein and, presumably, a soluble polysaccharide(s). Mosaic secretion ceases at about the time when juveniles settle on the sea bed, which more or less coincides with the secretion of a ring of lamellae around the mosaic, induced by rapid advances and retractions of the outer mantle lobe prior to deposition of the organophosphatic mature shell. Energy dispersion X-ray analyses of pelagic and newly settled juveniles show that phosphatic secretion, even in the site of the first-formed outer epithelial collective, does not begin until all siliceous secretion has ceased.

Animals↗
PubMed2000

Recent advances in ischaemic heart disease.

There continue to be important developments in the understanding of the pathogenesis of coronary artery disease. Advances have also been made in both the medical and interventional management of patients with ischaemic heart disease. This review has, however, not focused on the wider developments that have occurred in the area of percutaneous intervention. The vast array of new stent designs and other interventional devices have had a considerable impact on the treatment of obstructive coronary disease. In addition it is likely that further developments will be seen in areas such as intracoronary radiotherapy to reduce restenosis after PTCA and in gene therapy to promote angiogenesis in ischaemic myocardium. Both of which will be discussed in a future review of this area.

Angina Pectoris↗
PubMed1999

Evolution of a rhythmic lamination in the organophosphatic shells of brachiopods

The secondary layer of organophosphatic-shelled brachiopods consists of stratiform laminae in glycosaminoglycans (GAGs), pervaded by canals with chitinous walls. The laminae are composed of various aggregates of protein-coated granules of apatite, 4-8 nm in size, 10 or so soluble proteins, beta-chitinous meshes and sheets, and a possibly proteinaceous actin-like network. The succession is disposed in rhythmic sets grading between predominantly apatitic and wholly membranous laminae. The most conspicuous set consists of apatitic rods (baculi) in trellised arrays associated with laminae of compacted mosaics and spherules of apatite. The baculi are composed of mosaics accreting around axial fibrous proteins; apatitic aggregates are also scattered throughout the GAGs and accrete on proteinaceous networks and chitinous meshes. Baculi, subtended between two compact laminae, first appeared in Early Cambrian times and are a synapomorphy of lingulides. Subsequently, the secretion of one or another of the compact laminae was suppressed in the two surviving clades, with sets of the lingulid Glottidia and the discinids, respectively, grading inwardly from, and to, compact laminae. Suppression of baculate secretion also occurred in the dorsal valve of living Discinisca while, in Lingula, baculi have been replaced by botryoidal aggregates of mosaics at least since Carboniferous times. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Renal function in chronically catheterized conscious diabetic rats using constant and servo-controlled infusion.

1. Infusion experiments were performed on chronically catheterized conscious rats to assess kidney function before and after the induction of diabetes mellitus with streptozotocin. 2. Two infusion regimens were used, a conventional constant-infusion protocol and a novel computer-driven, servo-controlled fluid replacement technique. The latter enables body fluid status to be maintained throughout a study occasion by servo-controlled replacement of spontaneous urinary fluid losses. 3. The chronically catheterized conscious rat infused using a servo-controlled system appears to be the optimum model for a study of diabetic renal function. The conscious preparation circumvents problems associated with anaesthesia and acute surgery. The servo-controlled infusion protocol maintains the altered fluid status of the diabetic condition. Both hyperfiltration and polyuria, characteristics of human diabetes often absent in anaesthetized and/or constantly infused diabetic rats, were seen in all conscious servo-controlled diabetic animals. 4. The new regimen enables a more accurate assessment of renal function in experimental diabetes than with previous protocols. It should prove useful in future studies, particularly those assessing the role of anti-diabetic drugs on the kidney.

Animals↗
PubMed1998

Siliceous tablets in the larval shells of apatitic discinid brachiopods

The marine bivalved Brachiopoda are abundant throughout the geological record and have apatitic (CaPO4-rich) or calcitic (CaCO3-rich) shells. Vesicles covering the larval valves of living apatitic-shelled discinids contain tablets of silica. The tablets are cemented into close-packed mosaics by spherular apatite in glycosaminoglycans. They are usually lost as vesicles degrade but leave imprints on the underlying apatitic shell. Similar imprints ornament larval surfaces of some of the earliest Paleozoic apatitic-shelled brachiopods and may also be indicators of siliceous biomineralization.

Journal Article↗
PubMed1992

An intracrystalline chromoprotein from red brachiopod shells: implications for the process of biomineralization.

1. The red colour of some terebratulid brachiopod shells is caused by a small chromoprotein that occurs within the calcium carbonate matrix of the shell. 2. This carotenoid-protein complex was isolated from within the calcite shell of three different brachiopod genera and may therefore be involved in the process of biomineralization. 3. The apparent molecular weight of this protein, as judged by SDS-PAGE, is 6.5 kDa. 4. The partial N-terminal amino acid sequence of the protein is virtually identical in three different brachiopod genera, indicating homology. 5. Two carotenoids are present in Terebratella sanguinea: canthaxanthin and the tentatively identified monoacetylinic analogue of astaxanthin.

Amino Acid Sequence↗
PubMed1991

Purification and characterization of thaumatopain, a cysteine protease from the arils of the plant Thaumatococcus daniellii.

Aqueous extracts of the aril of the seed of Thaumatococcus daniellii contain, in addition to the intensely sweet protein thaumatin, a cysteine protease that we have termed thaumatopain. Thaumatopain has been purified by ion-exchange chromatography from arils, and is a monomeric protein of Mr 30,000. The protease strongly resembles papain in proteolytic activity, pH optima, susceptibility to inhibitors of cysteine proteases and in N-terminal sequence. The protease has also been identified in crude aril extracts by affinity labelling with iodo[14C]acetate. Thaumatopain is responsible for the cysteine protease activity previously attributed to thaumatin. Thaumatin is digested by thaumatopain at neutral to alkaline pH values.

Amino Acid Sequence↗
PubMedDate not supplied

Combining work and home.

The health consequences for women of combining work outside the home with domestic responsibilities are reviewed. The chapter evaluates role stress as a function of multiple roles and concludes that such juggling promotes women's health by offering increased variety of functions performed as well as increased emotional buffering. The chapter also concludes that women's working outside the home has a positive effect likewise on children and spouses.

Female↗