Annals of medicine
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The adipsin-ASP pathway provides a mechanism by which the adipocyte is able to regulate its rate of de novo triglyceride synthesis and reesterification. The adipocyte can synthesize and secrete the three proteins necessary for the formation of the effector molecule, acylation stimulating protein (ASP). ASP increases membrane transport of glucose and the activity of diacylglycerol acyltransferase and by virtue of both of these effects markedly increases the rate of triglyceride synthesis. ⋯ Accordingly, the concept of microenvironmental metabolic regulation of triglyceride hydrolysis at the endothelial surface and triglyceride synthesis within the adipocyte will be presented. In addition, the pathogenetic sequence by which dysfunction of this pathway can lead to dyslipoproteinaemia will be reviewed. Emphasis, however, will be placed on the role this pathway may play in the pathogenesis of obesity and the adaptation to negative caloric balance in the obese.
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Apolipoprotein B (apo B) circulates in two distinct forms referred to as apo B100 and apo B48. Apo B48 is colinear with the amino-terminal half of apo B100 and arises as a result of a post-transcriptional modification, termed apo B mRNA editing. This process changes a single cytidine nucleotide in apo B100 mRNA thereby altering a CAA codon, encoding glutamine in apo B100, to a UAA codon, which specifies an in-frame stop codon in apo B48. ⋯ These differences arise because the requisite regions of apo B for interaction either with the low-density lipoprotein receptor or with apolipoprotein (a) are contained within the carboxyl terminus of apo B100. Apo B mRNA editing is regulated by species, tissue and cell-specific factors, one of which has been recently cloned. The further characterization of apo B mRNA editing, the first example of a mammalian gene regulated by post-transcriptional nucleotide alteration, will be important for an understanding of lipoprotein assembly.
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The pathogenesis of nutritional rickets is not well-understood. While the etiologies include deficiencies of vitamin D, calcium (Ca) or phosphate (PO4), and perhaps aluminium toxicity, the role these nutrients play in the development of tissue level anomalies characteristic of rachitic cartilage and bone has yet to be defined. Reported alterations in the biochemistry of rachitic bone and cartilaginous matrix which could adversely affect mineralization and endochondral ossification are of questionable significance since the tissues mineralize rapidly when exposed to Ca and PO4 salts in vivo and in vitro. ⋯ In healing rickets, the Ca and PO4 content of these tissue fluids increases in the same time-frame it takes to experimentally remineralize the matrices. However, it is not certain what determines the Ca and PO4 content of the ECF. Cytokines which may play a role in the cellular regulation of Ca and PO4 and maintain processes which contribute to normal patterns of endochondral ossification could provide a mechanism common to the pathogenesis of rickets from a variety of causes.
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Ethics is an essential dimension of the practice of obstetric ultrasound. This paper addresses four important areas in which ethics is especially relevant: competence and referral, disclosure, confidentiality, and routine screening.