Acreage Living, December 2004-January 2005

Newsletter for those who reside on acreages

Digestion of Streptococcus pneumoniae cell walls with its major peptidoglycan hydrolase releases branched stem peptides carrying proinflammatory activity.

The peptidoglycan of Gram-positive bacteria is known to trigger cytokine release from peripheral blood mononuclear cells (PBMCs). However, it requires 100-1000 times more Gram-positive peptidoglycan than Gram-negative lipopolysaccharide to release the same amounts of cytokines from target cells. Thus, either peptidoglycan is poorly active or only part of it is required for PBMC activation. To test this hypothesis, purified Streptococcus pneumoniae walls were digested with their major autolysin N-acetylmuramoyl-L-alanine amidase, and/or muramidase. Solubilized walls were separated by reverse phase high pressure chromatography. Individual fractions were tested for their PBMC-stimulating activity, and their composition was determined. Soluble components had a Mr between 600 and 1500. These primarily comprised stem peptides cross-linked to various extents. Simple stem peptides (Mr <750) were 10-fold less active than undigested peptidoglycan. In contrast, tripeptides (Mr >1000) were >/=100-fold more potent than the native material. One dipeptide (inactive) and two tripeptides (active) were confirmed by post-source decay analysis. Complex branched peptides represented </=2% of the total material, but their activity (w/w) was almost equal to that of LPS. This is the first observation suggesting that peptidoglycan stem peptides carry high tumor necrosis factor-stimulating activity. These types of structures are conserved among Gram-positive bacteria and will provide new material to help elucidate the mechanism of peptidoglycan-induced inflammation.

Association with coregulators is the major determinant governing peroxisome proliferator-activated receptor mobility in living cells.

The nucleus is an extremely dynamic compartment, and protein mobility represents a key factor in transcriptional regulation. We showed in a previous study that the diffusion of peroxisome proliferator-activated receptors (PPARs), a family of nuclear receptors regulating major cellular and metabolic functions, is modulated by ligand binding. In this study, we combine fluorescence correlation spectroscopy, dual color fluorescence cross-correlation microscopy, and fluorescence resonance energy transfer to dissect the molecular mechanisms controlling PPAR mobility and transcriptional activity in living cells. First, we bring new evidence that in vivo a high percentage of PPARs and retinoid X receptors is associated even in the absence of ligand. Second, we demonstrate that coregulator recruitment (and not DNA binding) plays a crucial role in receptor mobility, suggesting that transcriptional complexes are formed prior to promoter binding. In addition, association with coactivators in the absence of a ligand in living cells, both through the N-terminal AB domain and the AF-2 function of the ligand binding domain, provides a molecular basis to explain PPAR constitutive activity.

Estimation of the viscoelastic properties of vessel walls using a computational model and Doppler ultrasound

Human arteries affected by atherosclerosis are characterized by altered wall viscoelastic properties. The possibility of noninvasively assessing arterial viscoelasticity in vivo would significantly contribute to the early diagnosis and prevention of this disease. This paper presents a noniterative technique to estimate the viscoelastic parameters of a vascular wall Zener model. The approach requires the simultaneous measurement of flow variations and wall displacements, which can be provided by suitable ultrasound Doppler instruments. Viscoelastic parameters are estimated by fitting the theoretical constitutive equations to the experimental measurements using an ARMA parameter approach. The accuracy and sensitivity of the proposed method are tested using reference data generated by numerical simulations of arterial pulsation in which the physiological conditions and the viscoelastic parameters of the model can be suitably varied. The estimated values quantitatively agree with the reference values, showing that the only parameter affected by changing the physiological conditions is viscosity, whose relative error was about 27% even when a poor signal-to-noise ratio is simulated. Finally, the feasibility of the method is illustrated through three measurements made at different flow regimes on a cylindrical vessel phantom, yielding a parameter mean estimation error of 25%.

Acreage Living, December 1999, Vol 5, no.9

Acreage Living newsletter for those persons living on or interested in acreage living.

Acreage Living, March 2000, Vol 6, no.3

Acreage Living newsletter for those persons living on or interested in acreage living.

Acreage Living, May 2000, Vol.6, no.5

Monthly newsletter for people in Iowa that live on Acreages, produced by Iowa State University Copperative Extension.

Acreage Living, January 2000, Vol.6, no.1

Monthly newsletter for people in Iowa that live on Acreages, produced by Iowa State University Copperative Extension.

Acreage Living, February 2000, Vol.6, no.2

Monthly newsletter for people in Iowa that live on Acreages, produced by Iowa State University Copperative Extension.

Acreage Living, April 2000, Vol.6, no.4

Monthly newsletter for people in Iowa that live on Acreages, produced by Iowa State University Copperative Extension.

Acreage Living, June 2000, Vol.6, no.6

Monthly newsletter for people in Iowa that live on Acreages, produced by Iowa State University Copperative Extension.

Acreage Living, April 2002, Vol.8, no.4

Monthly newsletter for people in Iowa that live on Acreages, produced by Iowa State University Copperative Extension.

Acreage Living, July 2000, Vol.6, no.5

Monthly newsletter for people in Iowa that live on Acreages, produced by Iowa State University Copperative Extension.

Acreage Living, August 2000, Vol.6, no.8

Monthly newsletter for people in Iowa that live on Acreages, produced by Iowa State University Copperative Extension.

Acreage Living, September 2000, Vol.6, no.9

Monthly newsletter for people in Iowa that live on Acreages, produced by Iowa State University Copperative Extension.