Hasil untuk "Physiology"

E. Niki

J. Travis, G. Salvesen

L. Csonka

The capacity of organisms to respond to fluctuations in their osmotic environments is an important physiological process that determines their abilities to thrive in a variety of habitats. The primary response of bacteria to exposure to a high osmotic environment is the accumulation of certain solutes, K+, glutamate, trehalose, proline, and glycinebetaine, at concentrations that are proportional to the osmolarity of the medium. The supposed function of these solutes is to maintain the osmolarity of the cytoplasm at a value greater than the osmolarity of the medium and thus provide turgor pressure within the cells. Accumulation of these metabolites is accomplished by de novo synthesis or by uptake from the medium. Production of proteins that mediate accumulation or uptake of these metabolites is under osmotic control. This review is an account of the processes that mediate adaptation of bacteria to changes in their osmotic environment.

H. Helmholtz, A. Ellis

Y. Kawaguchi, Charles J. Wilson, S. Augood et al.

S. Lord, H. Menz, A. Tiedemann

J. Goff, R. Horst

J. Metz, O. Diekmann

M. Kreek, D. Nielsen, E. Butelman et al.

A. Bookout, Yangsik Jeong, M. Downes et al.

In multicellular organisms, the ability to regulate reproduction, development, and nutrient utilization coincided with the evolution of nuclear receptors (NRs), transcription factors that utilize lipophilic ligands to mediate their function. Studying the expression profile of NRs offers a simple, powerful way to obtain highly relational information about their physiologic functions as individual proteins and as a superfamily. We surveyed the expression of all 49 mouse NR mRNAs in 39 tissues, representing diverse anatomical systems. The resulting data set uncovers several NR clades whose patterns of expression indicate their ability to coordinate the transcriptional programs necessary to affect distinct physiologic pathways. Remarkably, this regulatory network divides along the following two physiologic paradigms: (1) reproduction, development, and growth and (2) nutrient uptake, metabolism, and excretion. These data reveal a hierarchical transcriptional circuitry that extends beyond individual tissues to form a meganetwork governing physiology on an organismal scale.

S. Nardi, D. Pizzeghello, A. Muscolo et al.

D. Barañano, Mahil Rao, C. D. Ferris et al.

B. Folkow

L. Ernster, Gustav Dallner, Gustav Dallner

L. Lipsitz, A. Goldberger

Steven B. Zimmerman, Allen P. Minton

G. Wilkinson, D. Shand

W. Miller

J. Graham, Christine L. Clarke

C. Horan

Thyroid and parathyroid gland Thyroxine-binding globulin (TBG) concentrations rise due to increased oestrogen levels. T4 and T3 increase over the first half of pregnancy but there is a normal to slightly decreased amount of free hormone due to increased TBG-binding. Normal ranges are slightly reduced in the second and third trimester. TSH production is stimulated after the first trimester, although in healthy individuals this is not usually significant. A large rise in TSH is likely to indicate iodine deficiency or subclinical hypothyroidism. Women are relatively iodine-deficient in pregnancy; the World Health Organization (WHO) recommends an increased intake during this time. [3, 4]Where iodised salt is unavailable, supplements are recommended. If iodine levels are maintained in pregnancy, the thyroid gland should stay the same size and any increase be investigated. It will be larger in the presence of iodine deficiency. Although fetal need for calcium is high, maternal serum calcium levels are maintained in pregnancy by increased intestinal absorption. There is also increased excretion in the urine, as a result of which pregnant women are at increased risk of renal stones. Colecalciferol (vitamin D3) is converted to its active metabolite, 1,25-dihydroxycolecalciferol, by placental 1α-hydroxylase. Serum levels rise and are responsible for the increased intestinal absorption of calcium.