Revisiting the bilayer structures of fluid phase phosphatidylglycerol lipids: Accounting for exchangeable hydrogens

We recently published two papers detailing the structures of fluid phase phosphatidylglycerol (PG) lipid bilayers (Ku?erka et al., 2012 J. Phys. Chem. B 116: 232–239; Pan et al., 2012 Biochim. Biophys. Acta Biomembr. 1818: 2135–2148), which were determined using the scattering density profile model. This hybrid experimental/computational technique utilizes molecular dynamics simulations to parse a lipid bilayer into components whose volume probabilities follow simple analytical functional forms. Given the appropriate scattering densities, these volume probabilities are then translated into neutron scattering length density (NSLD) and electron density (ED) profiles, which are used to jointly refine experimentally obtained small angle neutron and X-ray scattering data. However, accurate NSLD and ED profiles can only be obtained if the bilayer's chemical composition is known. Specifically, in the case of neutron scattering, the lipid's exchangeable hydrogens with aqueous D₂O must be accounted for, as they can have a measureable effect on the resultant lipid bilayer structures. This was not done in our above-mentioned papers. Here we report on the molecular structures of PG lipid bilayers by appropriately taking into account the exchangeable hydrogens. Analysis indicates that the temperature-averaged PG lipid areas decrease by 1.5 to 3.8 Å², depending on the lipid's acyl chain length and unsaturation, compared to PG areas when hydrogen exchange was not taken into account.     

An immunohistochemical study of the pancreatic endocrine cells of the ddN mouse

The regional distribution and frequency of the pancreatic endocrine cells in the ddN mouse were studied using specific antisera against insulin, glucagon, somatostatin and human pancreatic polypeptide (hPP). In the pancreatic islets, most of insulin-immunoreactive (IR) cells were located in the central region, and glucagon-, somatostatin and hPP-IR cells were located in the peripheral region regardless of the lobe. In the splenic part, glucagon-IR cells were also located in the central regions, and more numerous somatostatin-IR cells were detected in the central regions as compared with the duo-denal part. hPP-IR cells were restricted to the peripheral regions in both lobes but more numerous cells were detected in the duodenal portion. In the exocrine parenchyma of the splenic lobe, only insulin- and glucagon-IR cells were detected but all four kinds of IR cells were observed in the duodenal portion. In addition, insulin and hPP-IR cells were also demonstrated in the pancreatic duct regions. In conclusion, some strain-dependent characteristic distributional patterns of pancreatic endocrine cells were found in the ddN mouse with somewhat different distributional patterns between the two pancreatic lobes.     

Monolayer formation of human osteoblastic cells on vertically aligned multiwalled carbon nanotube scaffolds

Monolayer formation of SaOS‐2 (human osteoblast‐like cells) was observed on VACNT (vertically aligned multiwalled carbon nanotubes) scaffolds without purification or functionalization. The VACNT were produced by a microwave plasma chemical vapour deposition on titanium surfaces with nickel or iron as catalyst. Cell viability and morphology studies were evaluated by LDH (lactate dehydrogenase) release assay and SEM (scanning electron microscopy), respectively. The non‐toxicity and the flat spreading with monolayer formation of the SaOs‐2 on VACNT scaffolds surface indicate that they can be used for biomedical applications.     

Influence of the acetylcholinesterase active site protonation on omega loop and active site dynamics

Existence of alternative entrances in acetylcholinesterase (AChE) could explain the contrast between the very high AChE catalytic efficiency and the narrow and long access path to the active site revealed by X-ray crystallography. Alternative entrances could facilitate diffusion of the reaction products or at least water and ions from the active site. Previous molecular dynamics simulations identified side door and back door as the most probable alternative entrances. The simulations of non-inhibited AChE suggested that the back door opening events occur only rarely (0.8% of the time in the 10ns trajectory). Here we present a molecular dynamics simulation of non-inhibited AChE, where the back door opening appears much more often (14% of the time in the 12ns trajectory) and where the side door opening was observed quite frequently (78% of trajectory time). We also present molecular dynamics, where the back door does not open at all, or where large conformational changes of the AChE omega loop occur together with alternative passage opening events. All these differences in AChE dynamical behavior are caused by different protonation states of two glutamate residues located on bottom of the active site gorge (Glu202 and G450 in Mus musculus AChE). Our results confirm the results of previous molecular dynamics simulations, expand the view and suggest the probable reasons for the overall conformational behavior of AChE omega loop.     

Modulation of granulocyte functions by peptide YY in the rat: Age-related differences in Y receptors expression and plasma dipeptidyl peptidase 4 activity

It has been acknowledged that aging exerts detrimental effects on cells of the innate immune system and that neuropeptides, including neuropeptide Y (NPY) and NPY-related peptides fine-tune the activity of these cells through a receptor specific mechanism. The present study investigated the age-dependent potential of peptide YY (PYY) to modulate different granulocyte functions. The PYY reduced the carrageenan-elicited granulocyte accumulation into the air-pouch of aged (24 months) rats, and markedly decreased the phagocytosis of zymosan, as well as the H₂O₂ production, when applied in vivo (20 μg/air-pouch). The anti-inflammatory effect of PYY was less prominent in adult (8 months) and young (3 months) rats. However, the proportions of granulocytes expressing Y1, Y2 and Y5 receptor subtypes were significantly lower in both aged and young rats when compared to adult rats. Furthermore, the aging was found to be associated with the diminished dipeptidyl peptidase 4 (DP4, an enzyme converting the NPY and PYY to Y2/Y5 receptor selective agonists) activity in plasma. In conclusion, the diverse age-related anti-inflammatory effect of PYY in rats originates from different expression levels of Y1, Y2, and Y5 receptor subtypes in addition to different plasma DP4 activity.     

Quantitative trait loci mapping of leaf angle and leaf orientation value in maize (Zea mays L.)

A major limiting factor for high productivity of maize (Zea mays L.) in dense planting is light penetration through the canopy. Plant architecture with a narrower leaf angle (LA) and an optimum leaf orientation value (LOV) is desirable to increase light capture for photosynthesis and production per unit area. However, the genetic control of the plant architecture traits remains poorly understood in maize. In this study, QTL for LA, LOV, and related traits were mapped using a set of 229 F_2:3 families derived from the cross between compact and expanded inbred lines, evaluated in three environments. Twenty-five QTL were detected in total. Three of the QTL explained 37.4% and five of the QTL explained 53.9% of the phenotypic variance for LA and LOV, respectively. Two key genome regions controlling leaf angle and leaf orientation were identified. qLA1 and qLOV1 at nearest marker umc2226 on chromosome 1.02 accounted for 20.4 and 23.2% of the phenotypic variance, respectively; qLA5 and qLOV5 at nearest bnlg1287 on chromosome 5 accounted for 9.7 and 9.8% of the phenotypic variance, respectively. These QTL could provide useful information for marker-assisted selection in improving performance of plant architecture with regard to leaf angle and orientation.     

Occurrence and fate of fetal lumbar rib induced by Scutellariae radix in rats

BACKGROUND: This study was conducted to evaluate the occurrence and fate of fetal lumbar rib induced by Scutellariae radix (SR) in rats. METHODS: Water extracts of SR were orally administered to pregnant rats from day 7 to day 17 of gestation at a dose of 186 mg/kg/day, equivalent to 25 g/kg of starting material, representing a 100‐fold increase over typical human intake level. RESULTS: The incidence of fetal lumbar rib in the SR‐treated group was increased on gestational day 20 and then decreased on postnatal day 50. The weight of fetuses in the SR‐treated group tended to be less than that in the control group. Alkaline phosphatase in SR‐treated dams was increased on gestational day 20, but was decreased on postnatal day 50. There were no significant differences between the vehicle control and SR‐treated groups in maternal body weight, embryological, histopathological, hematological, and serum biochemical changes. CONCLUSIONS: The present data suggest that the appearance of lumbar rib induced by SR is a transient fetal variation rather than teratogenicity or maternal toxicity. Birth Defects Res (Part B) 89:201–206, 2010. © 2010 Wiley‐Liss, Inc.     

Browning of chitooligomers and their optimum preservation

Chitooligomers have attracted much interest due to their unique biological activities. However, chitooligomers easily turn brown during shelf life. The factors influencing the browning of chitooligomers were investigated. The results indicated that the browning was attributed to the structure change of chitooligomers. The water-solubility, thermal stability and moisture–adsorption of chitooligomers decreased with the increase of browning. The time, temperature, pH, moisture, oxygen and reductant all had effect on the browning of chitooligomers. The optimal preservation condition for chitooligomers should be at low temperature and humidity, at pH below 4 or above 10, and in absence of oxygen.