Lactose Synthesis

This chapter is related to lactose synthesis, its chemistry, regulation, and differences between species, especially in cattle. Lactose synthesis takes place in the Golgi apparatus of mammary epithelial cells (MEC) by the lactose synthase (LS) enzyme complex from two precursors, glucose and UDP-galactose. The enzyme complex is formed by galactosyltransferase, and it is associated with α-lactalbumin. Importantly, the lactose secreted determines the volume of milk produced, due to its osmotic properties. Milk contains 5% lactose and 80% water, percentages that remain constant during lactation in the different mammalian species. The low variation in milk lactose content indicates that lactose synthesis remains constant throughout the period of lactation and that is highly conserved in all mammals. Lactose synthesis is initiated during the first third of the pregnancy, increasing after birth and placenta removal. Different glucose transporters have been involved in mammary glucose uptake, mainly facilitative glucose transporters GLUT1, GLUT8, and GLUT12 and sodium-glucose transporter SGLT1, with more or less participation depending on mammal species.

Search for the Origin of Discrepancies in Osmotic Measurements of the PNIPAM - Water System

Major, still unelucidated, inconsistencies exist in the literature among measurements of the thermodynamic properties of poly(N-isopropylacrylamide) (PNIPAM) solutions and gels. This paper looks for evidence of intrinsic ionic behaviour in cross-linked PNIPAM homopolymer hydrogels synthesized in water under standard conditions. Systematic measurements are made of the swelling and osmotic properties of lightly cross-linked PNIPAM hydrogels, as well as of their potentiometric titration and DSC response, over a wide range of pH and ionic strength conditions, in order to distinguish the effects of the latter two parameters on putative intrinsic ions. The intrinsic ion content of the gel is found to be vanishingly small, and consequently unlikely to be the source of the divergences among past measurements. By contrast, a major finding of this study is that comparison of the present results with the literature reveals that frustrated equilibrium can be a source of substantial discrepancies.

Hydrogel-enabled osmotic pumping for microfluidics: towards wearable human-device interfaces

This paper describes a technique that utilizes the osmotic properties of hydrogels to passively draw fluid through a membrane and pass it along to a microfluidic network for sensing purposes.