Dietary vitamin B6 supplementation attenuates hypertension in spontaneously hypertensive rats

In spontaneously hypertensive rats (SHRs) excess endogenous aldehydes bind sulfhydryl groups of membrane proteins, altering membrane Ca²⁺ channels, increasing cytosolic free calcium and blood pressure. N-acetyl cysteine normalizes elevated blood pressure in SHRs by binding excess endogenous aldehydes. It is known that dietary vitamin B6 supplementation can increase the level of endogenous cysteine. Our objective was to investigate whether a dietary supplementation of vitamin B6 can prevent hypertension and associated changes in SHRs. Starting at 7 weeks of age, animals were divided into three groups of six animals each. Animals in WKY-control group and SHR-control group were given a normal vitamin B6 diet; and SHR-vitamin B6 group, a high vitamin B6 diet (20 times the recommended dietary intake; RDA) for the next 14 weeks. After 14 weeks, systolic blood pressure, platelet [Ca²⁺]_i and liver, kidney and aortic aldehyde conjugates were significantly higher in SHR controls compared to WKY controls. These animals also showed smooth muscle cell hyperplasia in the small arteries and arterioles of the kidneys. Dietary vitamin B6 supplementation attenuated the increase in systolic blood pressure, tissue aldehyde conjugates and associated changes. These results further support the hypothesis that aldehydes are involved in increased systolic blood pressure in SHRs and suggest that vitamin B6 supplementation may be an effective antihypertensive.     

Neutron scattering measurements of intact cells show changes after heat shock consistent with an increase in molecular crowding

Molecular crowding has been shown to be important in many cellular processes. The crowded environment in the cell results in a significant proportion of the cellular water being in contact with macromolecules such as proteins and DNA. These interfacial water molecules show a reduced dynamic motion that has been observed with isolated macromolecules using several biophysical techniques. Previously we investigated the inelastic neutron scattering properties of water closely associated with isolated biomolecules, and showed that interfacial water is strongly perturbed, as judged by its energy transfer spectrum. Here we have probed living cells using inelastic and quasielastic neutron scattering. We have found that mild heat stress ('heat shock'), which causes some proteins to become unfolded in the cell, results in changes in the inelastic neutron scattering in the librational region (45-130 meV). Heat shock also causes a narrowing of the quasielastic scattering peak. These changes can be understood in terms of an increase in the proportion of interfacial water molecules, and a net reduction in proton dynamics.     

Changes in micronucleus frequency resulting from preirradiation of cell culture surfaces

We have initiated a series of experiments to quantify the impact of environmental variables on the observed frequency of micronuclei in monolayer cultures. In this paper the influence of preirradiation of cell culture vessels on micronucleus formation in Chinese hamster ovary cells was examined. Dry cell culture vessels were preirradiated with 2 Gy of either alpha particles or X rays and immediately plated with nonirradiated cells. About 48 h later a group of randomly chosen containers was set aside, and the rest of the containers were exposed to a range of doses of X rays or alpha-particle radiation. Nonirradiated cells plated on previously irradiated cell culture surfaces manifested nearly as many micronuclei as the irradiated cells. In all experiments, preirradiation of the cell substrate (the culture dish) led to a significantly increased micronucleus frequency relative to unirradiated substrate. These results suggest that methods of cell culture vessel sterilization and the composition of cell attachment surfaces could be a confounding factor, particularly in low-dose experiments.     

Construction of a linkage map based on a <Emphasis Type="Italic">Lathyrus sativus</Emphasis> backcross population and preliminary investigation of QTLs associated with resistance to ascochyta blight

A linkage map of the Lathyrus sativus genome was constructed using 92 backcross individuals derived from a cross between an accession resistant (ATC 80878) to ascochyta blight caused by Mycosphaerella pinodes and a susceptible accession (ATC 80407). A total of 64 markers were mapped on the backcross population, including 47 RAPD, seven sequence-tagged microsatellite site and 13 STS/CAPS markers. The map comprised nine linkage groups, covered a map distance of 803.1 cM, and the average spacing between markers was 15.8 cM. Quantitative trait loci (QTL) associated with ascochyta blight resistance were detected using single-point analysis and simple and composite interval mapping. The backcross population was evaluated for stem resistance in temperature-controlled growth room trials. One significant QTL, QTL1, was located on linkage group 1 and explained 12% of the phenotypic variation in the backcross population. A second suggestive QTL, QTL2, was detected on linkage group 2 and accounted for 9% of the trait variation. The L. sativus R-QTL regions detected may be targeted for future intergenus transfer of the trait into accessions of the closely related species Pisum sativum.     

PPARalpha agonists stimulate progastrin production in human colorectal carcinoma cells

The three subtypes of peroxisome proliferator activated-receptors (PPARalpha, delta and gamma) control the storage and metabolism of fatty acids. Treatment of rats with the PPARalpha ligand ciprofibrate increases serum gastrin concentrations, and several lines of evidence suggest that non-amidated gastrins act as growth factors for the colonic mucosa. The aim of the present study was to investigate the expression of PPARs and the effect of PPAR ligands on gastrin production and cell proliferation in human colorectal carcinoma (CRC) cell lines. mRNAs for all three PPAR subtypes were detected by PCR in all CRC cell lines tested. The concentrations of progastrin, but not of glycine-extended or amidated gastrin, measured by radioimmunoassay in LIM 1899 conditioned media and cell extracts were significantly increased by treatment with the PPARalpha ligand clofibrate. Similar increases in progastrin were seen following treatment with the PPARalpha ligands ciprofibrate and fenofibrate, but not with bezafibrate, gemfibrozil or Wy 14643. The PPARgamma agonist rosiglitazone had no significant effect on progastrin production. The PPARalpha ligand clofibrate also stimulated proliferation of the LIM 1899 cell line. We conclude that some PPARalpha ligands increase progastrin production by the human CRC cell line LIM 1899, and that clofibrate increases proliferation of LIM 1899 cells. These studies have revealed a relationship between PPARs and gastrin, two regulatory molecules implicated in the pathogenesis of CRC.     

Evolving nature of the AP2 alpha-appendage hub during clathrin-coated vesicle endocytosis

Clathrin-mediated endocytosis involves the assembly of a network of proteins that select cargo, modify membrane shape and drive invagination, vesicle scission and uncoating. This network is initially assembled around adaptor protein (AP) appendage domains, which are protein interaction hubs. Using crystallography, we show that FxDxF and WVxF peptide motifs from synaptojanin bind to distinct subdomains on alpha-appendages, called 'top' and 'side' sites. Appendages use both these sites to interact with their binding partners in vitro and in vivo. Occupation of both sites simultaneously results in high-affinity reversible interactions with lone appendages (e.g. eps15 and epsin1). Proteins with multiple copies of only one type of motif bind multiple appendages and so will aid adaptor clustering. These clustered alpha(appendage)-hubs have altered properties where they can sample many different binding partners, which in turn can interact with each other and indirectly with clathrin. In the final coated vesicle, most appendage binding partners are absent and thus the functional status of the appendage domain as an interaction hub is temporal and transitory giving directionality to vesicle assembly.     

Muscarinic M2 antagonists: anthranilamide derivatives with exceptional selectivity and in vivo activity

Anthranilamide analogues such as 23 are potent and highly selective muscarinic M2 antagonists that also show good oral bioavailability and in vivo activity.     

Cell balance equation for chemotactic bacteria with a biphasic tumbling frequency

Alts three-dimensional cell balance equation characterizing the chemotactic bacteria was analyzed under the presence of one-dimensional spatial chemoattractant gradients. Our work differs from that of others who have developed rather general models for chemotaxis in the use of a non-smooth anisotropic tumbling frequency function that responds biphasically to the combined temporal and spatial chemoattractant gradients. General three-dimensional expressions for the bacterial transport parameters were derived for chemotactic bacteria, followed by a perturbation analysis under the planar geometry. The bacterial random motility and chemotaxis were summarized by a motility tensor and a chemotactic velocity vector, respectively. The consequence of invoking the diffusion-approximation assumption and using intrinsic one-dimensional models with modified cellular swimming speeds was investigated by numerical simulations. Characterizing the bacterial random orientation after tumbles by a turn angle probability distribution function, we found that only the first-order angular moment of this turn angle probability distribution is important in influencing the bacterial long-term transport. Mathematics Subject Classification (2000):60G05, 60J60, 82A70     

Structure-function correlation in airway smooth muscle adapted to different lengths

Airway smooth muscle is able to adapt and maintain a nearly constant maximal force generation over a large length range. This implies that a fixed filament lattice such as that found in striated muscle may not exist in this tissue and that plastic remodeling of its contractile and cytoskeletal filaments may be involved in the process of length adaptation that optimizes contractile filament overlap. Here, we show that isometric force produced by airway smooth muscle is independent of muscle length over a twofold length change; cell cross-sectional area was inversely proportional to cell length, implying that the cell volume was conserved at different lengths; shortening velocity and myosin filament density varied similarly to length change: increased by 69.4% ± 5.7 (SE) and 76.0% ± 9.8, respectively, for a 100% increase in cell length. Muscle power output, ATPase rate, and myosin filament density also have the same dependence on muscle cell length: increased by 35.4% ± 6.7, 34.6% ± 3.4, and 35.6% ± 10.6, respectively, for a 50% increase in cell length. The data can be explained by a model in which additional contractile units containing myosin filaments are formed and placed in series with existing contractile units when the muscle is adapted at a longer length. muscle contraction; myosin filaments; ATPase activity; electron microscopy