Effects of Hydrogen Bonding on Diffusion of Aromatic Compounds in Acetone: An Experimental Investigation from 268.2 to 328.2 K.

Diffusion coefficients of pseudoplanar aromatic compounds at infinite dilution in acetone have been measured at different temperatures by the Taylor dispersion technique. The data of the polar solutes that can form hydrogen bonds with acetone are compared with those of the nonpolar ones incapable of hydrogen bonding to quantify the effects of hydrogen-bonded association on diffusion. The effects are further found to correlate strongly with the overall hydrogen-bonded acidity of the polar solutes containing proton-donating groups. For the nonpolar solutes in this study, the diffusivities at different temperatures can be expressed very well by the recently developed molecular-modified fractional Stokes-Einstein relation with only two constants. An innovative model for solute diffusion in liquid solutions, which is constructed by combining the molecular-hydrodynamic relation for nonpolar solutes with the overall hydrogen-bonded acidity scale for polar solutes, is introduced for representing the diffusivities of different types of disc-shaped molecules at various temperatures. An equation developed from this model is demonstrated to be capable of calculating a total of 191 diffusion data of both the hydrogen-bonded and the nonassociated aromatic solutes in acetone from 268.2 to 328.2 K to a standard deviation of 2.7%.

Diffusion of Aromatic Isomers in Acetone: An Investigation on the Effects of Intramolecular and Intermolecular Hydrogen Bonding.

Limiting mutual diffusivities of o- and m-isomers of methylaniline, nitroaniline, nitrophenol, and aminophenol were measured in acetone at 298.2 K by the Taylor dispersion method. The data reveal that all of the o-substituted solutes capable of intramolecular hydrogen bonding diffuse faster than their m-counterparts without such bonding. By taking into account of the small corrections for the differences in molecular shape and steric hindrance between the o- and m-isomers that can form solute-solvent complexes, the net effects of intramolecular hydrogen bonding were uncovered to render the o-isomers greater in diffusivity by 3-15% as compared to their m-isomers in this study. For aromatic amines and phenols diffusing in acetone, the overall effects of intermolecular hydrogen bonding on diffusivity were ascertained by comparing the available diffusivity data of the associated aromatic solutes with those of the nonassociated ones. The intermolecular effects that cause solutes to diffuse slower were found to vary from approximately 12-39% in the present work. The results indicate that both of the opposite intra- and intermolecular effects are significant. In addition, the quantified effects were analyzed to show that they are closely related to the nature and position of the functional groups contained in the aromatic solutes, including those that are unable to form hydrogen bonds with acetone. A relation that can correlate the diffusivities of the hydrogen-bonded aromatic amines and phenols in acetone with the overall acidities of the compounds is also presented.

Chronic treadmill running protects hippocampal neurons from hypobaric hypoxia-induced apoptosis in rats.

This study was designed to examine the effects of chronic running exercise (Ex) on the hypobaric hypoxia-induced neuronal injury in the hippocampus. Male Wistar rats (9 weeks old) were caged in a hypoxic altitude chamber simulating the condition of 9,000 m high (0.303 atm) for 7h and the brains were examined at 0, 4, and 24h after treatment. Hypoxia challenge increased the levels of caspase 3 (mean ± SEM, % of baseline control, 121.9 ± 11.8, 152.3 ± 15.3, 141.6 ± 7.0 for 0, 4 and 24h, respectively, n=5) and induced apoptosis (cell number, 205.7 ± 8.8, 342.3 ± 33.4, 403.0 ± 12.2 for 0, 4 and 24h vs. 7.7 ± 1.4 baseline control, n=3) in the hippocampal CA1 pyramidal neurons. The expression levels (% of control for 0, 4 and 24h, respectively, n=5) of hypoxia inducible factor-1α (HIF-1α; 150.5 ± 8.1, 176.7 ± 11.1, 136.2 ± 13.3), neuronal nitric oxide synthase (nNOS; 163.4 ± 9.6, 194.5 ± 13.6, 163.7 ± 10.9) and inducible nitric oxide synthase (iNOS; 139.4 ± 9.5, 169.2 ± 13.3, 134.3 ± 13.0) and the degrees of microglia (cell number, 255.3 ± 48.2, 349.0 ± 57.3, 433.7 ± 42.4 vs. 57.7 ± 13.0 baseline control, n=3) and astrocyte (150.0 ± 9.7, 199.3 ± 10.8, 154.2 ± 4.7) activation were increased by the hypoxia treatment, indicating that the brain was under hypoxic, oxidative and inflammatory stresses. Furthermore, the protein levels of hippocampal brain-derived neurotrophic factor (BDNF; 76.0 ± 2.5, 76.1 ± 7.1, 69.3 ± 1.7 for 0, 4 and 24h, respectively, mean % of control ± SEM, n=5) were reduced by the hypoxia treatment. Four weeks of treadmill Ex before hypoxia treatment significantly reduced the hypoxia-induced apoptosis (p<0.001, n=3) in the hippocampal CA1 neurons. Ex decreased the hypoxia-induced elevations of HIF-1α (p<0.001, n=5), nNOS (p<0.001, n=5) and iNOS (p<0.001, n=5) levels and activation of microglia (p=0.005, n=3) and astrocyte (p<0.001, n=5) status; whereas the hypoxia-reduced BDNF protein levels (p=0.013, n=5) were restored. Taken together, our results show that chronic Ex protects hippocampal CA1 neurons against hypobaric hypoxia insult. Ex-enhanced bioenergetic adaptation and anti-oxidative capacity may prevent neurons from hypoxia-induced apoptosis. Furthermore, activation of the BDNF signaling pathway may be involved in the Ex-induced protection.

Resonantly diode-pumped continuous-wave and Q-switched Er:YAG laser at 1645 nm.

We describe an efficient Er:YAG laser that is resonantly pumped using continuous-wave (CW) laser diodes at 1470 nm. For CW lasing, it emits 6.1 W at 1645 nm with a slope efficiency of 36%, the highest efficiency reported for an Er:YAG laser that is pumped in this manner. In Q-switched operation, the laser produces diffraction-limited pulses with an average power of 2.5 W at 2 kHz PRF. To our knowledge this is the first Q-switched Er:YAG laser resonantly pumped by CW laser diodes.

Alpinia pricei Hayata rhizome extracts have suppressive and preventive potencies against hypercholesterolemia.

The aim of this study was to investigate the effects of 70% ethanol extracts of Alpinia pricei (APE) on lipid profiles and lipid peroxidation. Syrian hamsters were fed a chow-based hypercholesterolemic diet (HCD) for 2 weeks to induce hypercholesterolemia (>250 mg/dl). To evaluate the potency of APE in suppressing hypercholesterolemia, hamsters were then fed HCD plus a high dose (500 mg/kg body weight) or a low dose (250 mg/kg body weight) of APE, or only HCD for another 4 weeks. We found that hypercholesterolemic hamsters fed a high dose of APE had lower serum total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C) levels, lower thiobarbituric acid reactive substances (TBARS) and alanine aminotransferase (ALT) activities, lower atherogenic indices (LDL-C/HDL-C and TC/HDL-C ratios), and lower hepatic protein expression of peroxisome proliferators activated receptor gamma (PPARgamma) than hamsters fed a HCD diet. In addition, we also determined the preventive effects of APE on hamsters fed a HCD for 6 weeks. The hypocholesterolemic effects were also found in hamsters co-fed a high dose of APE and HCD for 6weeks. These results suggest that APE has both suppressive and preventive potencies against hypercholesterolemia and has the potency to protect against lipid peroxidation.

Comparative effects of polyunsaturated- to saturated fatty acid ratio versus polyunsaturated- and monounsaturated fatty acids to saturated fatty acid ratio on lipid metabolism in rats.

This study examined the effects of various polyunsaturated fatty acid (PUFA, P)/saturated fatty acid (SFA, S) ratio versus PUFA + monounsaturated fatty acid (MUFA, M)/SFA ratio on lipid metabolism. The P/S ratio of dietary fat was fixed at a certain level (0.5, 1, 2, or 4, respectively) for each of four pairs of rat groups respectively, and then the P + M/S ratio was changed for the four pairs of rat groups. When the P/S ratio was fixed at 0.5, 1, 2, or 4, the plasma total cholesterol, LDL-cholesterol (C), and HDL-C levels did not show any significant difference in each pair of groups with different P + M/S ratios. However, when the P/S ratio was fixed at 1.0, the higher P + M/S ratio of 5.7 (M/S=4.7, P/M=0.2) resulted in significantly higher plasma total triacylglycerol (TAG), VLDL-TAG, VLDL-C, and VLDL-phospholipid (PL) than the lower P + M/S ratio of 1.4 (M/S=0.4, P/M=2.4). Whereas when SFA was fixed at a similar level, it therefore had approximately the same P + M/S ratio(5.3, 5.6, 5.7), and by increasing the P/S ratio from 1, 2 to 4 (70.4, 52.7 and 23.2% of the total fatty acids as MUFA respectively), the plasma VLDL-C, VLDL-TAG, and VLDL-PL concentrations decreased progressively. When PUFA or MUFA was kept on a similar level (14.9 or 53% respectively), the higher P + M/S ratio (5.7 or 5.3, respectively) resulted in significantly greater accumulation of liver cholesterol than the lower P + M/S ratio of 2.2. When the P/S ratio was fixed at 1 or 4, the diet of higher P + M/S ratio in a pair of the groups also resulted in greater accumulation of liver cholesterol. The results of the study suggests that if the P + M/S ratio was below 3, the change in the P/S ratios (0.5, 1 or 2) did not affect the levels of plasma total and lipoprotein cholesterol and TAG. Increases in the plasma VLDL-C and VLDL-TAG were related to increased MUFA content in the diet. And high MUFA content resulted in greater accumulation of liver cholesterol. It seems that the prerequisites for keeping low plasma and liver cholesterol are (a) low M/S ratio and (b) high P/M ratio and (c) P + M/S ratio not to exceed 3.

Effects of the ratio of polyunsaturated and monounsaturated fatty acid to saturated fatty acid on rat plasma and liver lipid concentrations.

The effects of dietary monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid + MUFA/saturated fatty acid (PUFA + MUFA/SFA) ratio on plasma and liver lipid concentrations were studied. In experiment I, when rats were fed with 40% fat (energy%, PUFA/SFA ratio 1.0) and 1% (w/w) cholesterol (C) diets for 21 d, a large amount of MUFA (28.1 energy%, PUFA + MUFA/SFA = 5.7) in the diet was found to increase the plasma total C, triacylglycerol (TAG), and phospholipid (PL) as compared with the low-MUFA diet (7.0 energy%, PUFA + MUFA/SFA = 1.4). The plasma very low density lipoprotein (VLDL)-C, VLDL-TAG, VLDL-PL, and low density lipoprotein (LDL)-C increased significantly in the high-MUFA diet group, but high density lipoprotein (HDL)-C did not change significantly. The high-MUFA diet resulted in greater accumulation of liver C but lesser accumulation of TAG. In experiment II, when dietary SFA was fixed at a certain level (13.2 energy%; PUFA + MUFA/SFA = 2.0), rats given a larger amount of MUFA (23.1 energy%; PUFA/MUFA = 0.2; MUFA/SFA = 1.8) showed higher plasma and liver C levels than did the low-MUFA diet (7.7 energy%; PUFA/MUFA = 2.5; MUFA/SFA = 0.6). When PUFA was fixed at a certain level (24.4 energy%), there was not a significant difference in the plasma C level between the high- and low-MUFA dietary groups (PUFA + MUFA/SFA = 4.8 and 8.4), but the higher PUFA + MUFA/SFA diet, which was high in MUFA/SFA ratio, significantly decreased the plasma HDL-C and TAG levels. However, when MUFA content was fixed at a certain level (16.4 energy%), no significant difference was observed between the two groups with different PUFA/SFA ratios of 0.2 and 4.1, but liver C level was raised in the higher PUFA/SFA diet. It appears that the PUFA/SFA ratio alone is unsuitable to predict the change of plasma C level, because a large amount of dietary MUFA may lead to an increase of plasma and liver lipids in rats. It seems that the prerequisites for keeping low plasma and liver C are (i) low MUFA/SFA ratio, (ii) high PUFA/MUFA ratio, and (iii) PUFA + MUFA/SFA ratio not to exceed 2.

An improved microinjection protocol for the transfer of Wolbachia pipientis between infected and uninfected strains of the flour beetle Tribolium confusum.

The lethality of halocarbon and other oils to hatching larvae of the flour beetle Tribolium confusum limits existing microinjection protocols, because postinjection survivorship is only 5.6% of the eggs injected. We report the development of an oil-free protocol that improves survivorship fivefold. We used this protocol to transfect the cytoplasmic endosymbiont Wolbachia pipientis from infected donor eggs to uninfected host eggs and observed reproductive incompatibility in 40% of the surviving, injected eggs. Compared with mock injected controls (35.9% survival) or microinjection of uninfected cytoplasm (32.3% survival), injection of Wolbachia-infected cytoplasm into host eggs significantly reduced egg-to-adult survival (25.1%).

Incipient speciation in the flour beetle, Tribolium confusum: premating isolation between natural populations.

We report the existence of partial reproductive isolation between two natural populations of the flour beetle, Tribolium confusum, collected in Kaduna, Nigeria and Zagreb, Croatia. When a female from either population is paired with a single sympatric or allopatric male, she produces near normal numbers of semifertile offspring. However, when females are multiply mated with allopatric and sympatric males, the sympatric males sire the large majority of offspring. When measured in offspring numbers, the mean relative fitness of allopatric males is 0.425 with Nigerian females and 0.085 with Croatian females. Thus, the reproductive isolation is reciprocal but asymmetric. Behavioural observations indicate that only a fraction of mating attempts by allopatric males are successful because females do not become quiescent as often when mounted by allopatric males. The premating isolation is also reciprocal but asymmetric: Nigerian females are more accepting of allopatric males as mates than are Croatian females. The prezygotic behavioural isolation between these two populations is different from the postmating, prezygotic isolation observed between two other species in the genus, T. castaneum and T. freemani. Furthermore, the T. confusum interpopulation hybrids are fertile although they exhibit a weak female bias.

Increased male fertility in Tribolium confusum beetles after infection with the intracellular parasite Wolbachia.

The cytoplasmically inherited microorganism Wolbachia pipientis behaves like a sexually selected trait in its host, the flour beetle Tribolium confusum, enhancing male fertility at the expense of female fecundity. Here we show that infected females have fewer offspring than uninfected females but infected males have a large fertility advantage over uninfected males within multiply-inseminated infected or uninfected females. The male fertility effect accelerates the spread of the Wolbachia through the host population and expands the initial opportunity for hitch-hiking of host nuclear genes. Sperm competition in a host, mediated by endosymbionts, has not been previously described.

Postcopulatory, prezygotic isolation in flour beetles.

We report the existence of postmating but prezygotic reproductive isolation within flour beetles of the genus Tribolium. Specifically, when a female of either T. castaneum or T. freemani is paired simultaneously with both a conspecific and a heterospecific male, virtually all of the offspring are sired by the conspecific male. In contrast, when a female of either species is paired only with a heterospecific male, she produces near normal numbers of offspring. Mate choice experiments rule out the possibility that premating reproductive isolation accounts for this phenomenon. A number of different mechanisms could explain this phenomenon of postmating but prezygotic reproductive isolation.

Effects of dietary monounsaturated fatty acids on plasma lipids in humans.

In order to test whether monounsaturated fatty acids (MUFA, M) would lower plasma cholesterol and/or triglycerides (TG), 14 young men were studied in a metabolism ward. They were given two experimental diets with the same P/S ratio (P: polyunsaturated; S:saturated fatty acids) but different P + M/S ratios in composition of dietary fatty acids. Six men were in experiment I. In two groups of three, each group was given either the high or the low P + M/S ratio diet for 6 weeks. In experiment II, two groups of four men were subjected to a 3-week cross-over feeding trial (total of 6 weeks). We found in the crossover study that when the dietary P/S ratio was fixed at 1.0, those subjects given a diet with the higher P + M/S ratio of 4.5 showed significantly higher plasma total TG, very low density lipoprotein (VLDL)-TG, low density lipoprotein (LDL)-TG, and LDL-cholesterol than when given a diet with a lower P + M/S ratio of 1.5. Plasma total cholesterol, apoprotein A-I, and apoprotein B-100 were not significantly different between the two dietary periods. Plasma fatty acid patterns showed a significantly higher plasma MUFA level during the period of a higher P + M/S diet. In contrast to some recent reports, our studies indicate that a large amount of dietary MUFA may raise some fractions of plasma lipids in humans.