Cell surface hydrophobicity of colistin-susceptible vs resistant Acinetobacter baumannii determined by contact angles: methodological considerations and implications.

Contact angle analysis of cell surface hydrophobicity (CSH) describes the tendency of a water droplet to spread across a lawn of filtered bacterial cells. Colistin-induced disruption of the Gram-negative outer membrane necessitates hydrophobic contacts with lipopolysaccharide (LPS). We aimed to characterize the CSH of Acinetobacter baumannii using contact angles, to provide insight into the mechanism of colistin resistance. Contact angles were analysed for five paired colistin-susceptible and resistant Ac. baumannii strains. Drainage of the water droplet through bacterial layers was demonstrated to influence results. Consequently, measurements were performed 0·66s after droplet deposition. Colistin-resistant cells exhibited lower contact angles (38·8±2·8-46·8±1·3°) compared with their paired colistin-susceptible strains (40·7±3·0-48·0±1·4°; anova; P<0·05). Contact angles increased at stationary phase (50·3±2·9-61·5±2·5° and 47·4±2·0-50·8±3·2°, susceptible and resistant, respectively, anova; P<0·05) and in response to colistin 32mgl(-1) exposure (44·5±1·5-50·6±2·8° and 43·5±2·2-48·0±2·2°, susceptible and resistant, respectively; anova; P<0·05). Analysis of complemented strains constructed with an intact lpxA gene, or empty vector, highlighted the contribution of LPS to CSH. Compositional outer-membrane variations likely account for CSH differences between Ac. baumannii phenotypes, which influence the hydrophobic colistin-bacterium interaction. Important insight into the mechanism of colistin resistance has been provided. Greater consideration of contact angle methodology is necessary to ensure accurate analyses are performed.

Genetic variation at the hormone sensitive lipase: gender-specific association with plasma lipid and glucose concentrations.

Hormone-sensitive lipase (HSL) catalyzes the intracellular hydrolysis of triacylglycerols and cholesteryl esters, and it is involved in regulating body fat, steroidogenesis, and insulin secretion. Thus, genetic variability at the HSL locus (LIPE) may play a significant role on lipid metabolism and the risk of obesity and type 2 diabetes. Therefore, we have examined two LIPE single nucleotide polymorphism (SNP) [14672C>G in the promoter region and 17948C>T (rs1206034) on intron 2] in relation to plasma lipids, anthropometrical and glucose-related phenotypes in a population of mostly overweight and obese men (373) and women (361). In women, the 17948T allele was associated with decreased total cholesterol (TC, p = 0.001), LDL-cholesterol (LDLc, p < 0.001) and apoE concentrations (p = 0.041). Conversely, female carriers of the LIPE 14672G allele had significantly higher TC (p = 0.047), LDLc (p = 0.041), and apoE (p = 0.041) levels. Although we did not find significant associations in men, we observed that male carriers of the LIPE 14672G who did not drink alcohol showed higher glucose levels than non-carriers (p = 0.008), whereas there were no allele-related differences among drinkers (p = 0.019 for the interaction). These SNPs were not significantly associated with anthropometrical variables. In summary, variation at this locus showed gender-specific associations with lipids and glucose measures, and the latter was influenced by alcohol drinking.

Effects of apolipoprotein A-IV genotype on glucose and plasma lipoprotein levels.

The effects of apolipoprotein (apo) A-IV genotype on serum glucose, total cholesterol, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, triglyceride and glucose concentrations were ascertained in a population of 373 men and 361 women with a mean age of about 57 years. Subjects were evaluated at entry into a lifestyle intervention program. Apolipoprotein A-IV genotype variations at residues 347 and 360 were examined, as these mutations affect the sequence of apo A-IV, a major protein constituent of intestinal triglyceride-rich lipoprotein and HDL. With regard to the apo A-IV 360 mutation, 16.4% of the females and 13.4% of the males carried the apo A-IV 2-allele, almost entirely in the heterozygous state. No effect of the apo A-IV 1/2 genotype was observed in either men or women on total cholesterol, LDL cholesterol, HDL cholesterol, triglyceride, the total cholesterol (TC)/HDL ratio, or on A-I, A-IV and apo B levels. This was also the case for the apo A-IV 347 mutation. However, women with the apo A-IV 360 1/2 genotype had significantly (p < 0.005) higher glucose levels (105.5 mg/dl) compared with the 1/1 wild-type (94.0 mg/dl). All analyses were also adjusted for age, body mass index, medications, alcohol use and cigarette smoking. The prevalence of the 347 mutation was somewhat higher than the 360 mutation, with 29% of the females and 32.0% of the males being heterozygous for this mutation, and 3.9% of the females and 5.4% of the males being homozygous for this mutation. These data are consistent with the concept that the apo A-IV 360 and 347 genotypes have no significant effect on apo A-IV levels and other lipid parameters in either gender. However, apo A-IV 360 1/2 genotype did have a significant effect on serum glucose levels in women.

Effects of apolipoprotein A-I genetic variations on plasma apolipoprotein, serum lipoprotein and glucose levels.

The present authors investigated the individual and combined associations of the apolipoprotein (apo) A-I -75 bp and +83 bp polymorphisms with plasma lipid, lipoprotein and apolipoprotein levels in 734 Caucasian men and women. The frequency of the A allele at position -75 bp (G-->A) was 0.14 in women and 0.17 in men. The frequencies for the rare M2 allele at position +83 bp and/or 84 bp (C-->T and G-->A, respectively) were 0.04 and 0.05 in women and men, respectively. In women, the A allele was associated with significantly higher levels of apo B (P = 0.016), total cholesterol (TC) (P = 0.005), low-density lipoprotein cholesterol (LDL-C) (P = 0.018) and TC:high-density lipoprotein (HDL) ratio (P = 0.026) compared to the G/G subjects. In men, no significant associations were detected between the -75 bp polymorphism and any lipid trait examined. The M2 allele for the +83 bp polymorphism was significantly associated in men with higher levels of apo A-I (P = 0.002) and TC (P = 0.046). In women, a significant effect was observed for TC (P = 0.036), with M2+/- subjects having lower levels than M2+/+ subjects. Significant linkage disequilibrium (P = 0.037) between the apo A-I -75 bp and +83 bp polymorphisms was detected. Women carrying both rare alleles (G/A M2+/-) had significantly higher TC:HDL ratios (P = 0.031) compared to the other haplotypes. In men, significant differences were observed for apo A-I (P = 0.021) and TC (P = 0.044), with carriers of the G/G M2+/- haplotype having the highest values compared to other genotype combinations. In conclusion, the -75 bp (G/A) polymorphism appears to have a significant effect on levels of apo B, plasma TC and LDL-C in women, while the +83 bp polymorphism seems to affect the apo A-I levels in men, and the plasma cholesterol levels in both genders.

Effects of age, gender, and lifestyle factors on plasma apolipoprotein A-IV concentrations.

Apolipoprotein (apo) A-IV is a protein component of triglyceride (TG)-rich lipoproteins and high density lipoproteins (HDL). Plasma apo A-IV levels were measured by immunoelectrophoresis and these values were related to other biological variables in 723 middle aged and elderly men and women (more than 90% of them were Caucasian) prior to participation in a lifestyle modification program. Apo A-IV may play an important function in regulating lipid absorption, reverse cholesterol transport, and food intake. The data are consistent with the following concepts: (1) apo A-IV levels are significantly and positively correlated with age (r = 0.159, P < 0.05) in all subjects, with plasma apo A-I levels in both men (r = 0.194, P < 0.001) and women (r = 0.213, P < 0.001), and with apo E (r=0.111, P<0.05) and TG levels (r =0.120, P <0.05) in men; (2) apo A-IV levels are inversely correlated with body mass index (r = 0.170, P <0.05) in women; (3) female subjects on hormone replacement therapy have significantly lower plasma apo A-IV levels (by 4.1%, P < 0.05) than normal controls; (4) diabetic subjects have significantly higher apo A-IV levels (by 21%, P < 0.01) than normal subjects; (5) there is no significant effect of smoking, alcohol intake, and apo A-IV-1/2 genotype on apo A-IV levels. The data indicate that plasma apo A-IV levels are significantly affected by age, diabetes, and hormone replacement therapy.

Surface Charge of Silver Iodide and Several Metal Oxides. Are All Surfaces Nernstian?

Charge titration data for silver iodide, titanium dioxide, aluminum oxide, silica dioxide and ferric hydroxide are analyzed using a generic site binding model that has the Nernst equation as a limiting form. Both the hypernetted chain and the nonlinear Poisson-Boltzmann approximations are used to relate the diffuse double-layer potential to the surface charge, and a zeroth-order Stern layer is used to give the surface potential. In all cases it is shown that in the vicinity of the point of zero charge the Nernst equation accurately gives the surface charge. Copyright 2000 Academic Press.

Association of apolipoprotein (Apo)E genotype with plasma apo E levels.

The purpose of this study was to investigate the effects of apolipoprotein (apo) E genotype on plasma apo E levels as well as serum total, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglyceride, and glucose values in 734 middle-aged and elderly, female and male subjects. Apo E allele frequencies were similar to those reported in other Caucasian populations. After adjustment for medications, alcohol use, smoking, age, and body mass index, apo E genotype was noted to have significant effects on apo E, total cholesterol, LDL cholesterol, and glucose levels in females, and on apo E, LDL cholesterol, and HDL cholesterol levels, as well as the total cholesterol (TC)/HDL cholesterol ratio in males. Female and male subjects with the apo E4 allele had significantly (P<0.05) lower plasma apo E (25 and 15%) and higher LDL cholesterol levels (5 and 2%), while those with the apo E2 allele had significantly (P<0.05) higher apo E (32 and 27%) and lower LDL cholesterol levels (10 and 10%) than the apo E3/3 group. Moreover, female apo E4 carriers had significantly (P<0.05) lower glucose values (11%) than the apo E3/3 group. These data are consistent with the concept that, in addition to the well known effects of apo E genotype on LDL-C values, this locus plays a very significant role in modulating plasma apo E levels.

The lipoprotein lipase HindIII polymorphism: association with total cholesterol and LDL-cholesterol, but not with HDL and triglycerides in 342 females.

BACKGROUND: Lipoprotein lipase (LPL) is the rate-limiting enzyme in the hydrolysis of core triglycerides in chylomicrons and VLDL. METHODS: We investigated the association between the HindIII polymorphism of the LPL gene and fasting glucose, lipid, and lipoprotein concentrations in 683 Caucasians. We first stabilized the study subjects, using an 8-day diet and exercise intervention program before obtaining blood samples. The use of this standardization period reduced the variance of all glucose and lipid concentrations. RESULTS: In our study, the HindIII allele frequencies for females and males were 0.29 and 0.34 for H- and 0.71 and 0.66 for H+, respectively. We found in females, but not in males, a significant association between the HindIII genotype and total cholesterol (P = 0.007) and LDL-cholesterol (P = 0.018), with females homozygous for the rare H- allele having the lowest, heterozygotes (H-/+) having intermediate, and women homozygous for the common H+ allele having the highest of each of these lipid traits. With regard to triglycerides, HDL-cholesterol, and glucose, no significant effect of the HindIII genotype was noted in either gender. CONCLUSIONS: These results suggest that in a gender-specific manner, the rare LPL HindIII H- allele has a cholesterol-lowering and, therefore, potentially cardioprotective effect compared with the common H+ allele.

Coagulation of Quartz Particles in Aqueous Solutions of Copper(II).

The colloidal stability of quartz suspension was determined over a wide range of pH in aqueous copper nitrate where the state of Cu(II) is changed from mainly aqua ions and monohydroxyl complexes in the acid and neutral pH to polynuclear hydroxo complexes and colloidal precipitated copper hydroxide at higher pH. Two regions of instability were observed and in both cases the particles were shown to have low electrophoretic mobility. In the neutral pH region, the uptake of Cu(II) was sufficient to reduce the mobility of the particles to zero, while in the high-pH region evidence suggested coagulation between precipitated Cu(OH)2 and the quartz particles. It was shown that in all cases the coagulation was reversible and that the uptake of Cu(II) was dependent on the uncharged surface hydroxyl density. Studies of the coagulation kinetics showed that extended time scales were involved (several minutes in the neutral pH region to tens of minutes at high pH). Copyright 1998 Academic Press.

Zonal differences in adrenocortical lipid peroxidation: role of alpha-tocopherol.

Studies were done to evaluate the relationship between alpha-tocopherol (alpha-T) concentrations and lipid peroxidation (LP) in vitro in microsomal preparations from the inner (zona reticularis) and outer (zona fasciculata plus zona glomerulosa) zones of the guinea pig adrenal cortex. Microsomes were incubated with ferrous ion (Fe2+) to promote free radical production, and alpha-T levels and LP were monitored after various incubation times. alpha-T concentrations were far lower in inner than outer zone preparations and were rapidly depleted from inner zone microsomes by incubation with Fe2+. Coinciding with alpha-T depletion was a large and rapid increase in LP. With outer zone microsomes, alpha-T depletion required more than 30 min, and very little LP was demonstrable during this period. However, once alpha-T depletion occurred, LP was rapidly initiated and reached levels similar to those obtained with inner zone preparations. Inhibition of LP by MnCl2 prevented the Fe(2+)-induced declines in alpha-T in both zones. The results demonstrate the importance of alpha-T as a modulator of adrenal LP and indicate that the zonal differences in LP are largely attributable to the differences in alpha-T concentrations.

Comparison of literacy level of patients in a VA arthritis center with the reading level required by educational materials.

Low literacy is a problem in a large segment of our population. We tested the reading levels of a group of 100 randomly chosen clinic and hospitalized patients seen in an urban Veterans Administration Arthritis and Immunology Center. The standardized Jastak Wide Range Achievement Test, revised level 2 (WRAT-R2), was utilized to determine the reading level appropriateness of Arthritis Foundation literature for this population. Arthritis Foundation literature by our testing with the McLaughlin's SMOG grading readability formula was found to be at the 8th- to 13th-grade level. Nearly 51% of our patients read below the 10th-grade level and 31% below the 7th-grade level. The Arthritis Foundation literature reading level may be too advanced for a significant number of our patients. These results may also have implications for other patient education literature and other written materials such as instructions on prescriptions.

Mechanism of action of spironolactone on cortisol production by guinea pig adrenocortical cells.

Studies were done to determine the mechanism(s) of action of spironolactone (SL) and of its deacetylated metabolite, 7 alpha-thio-SL, to inhibit cortisol secretion by guinea pig adrenocortical cells in vitro. Preincubation of cells at 37 degrees C with SL or with 7 alpha-thio-SL caused a time-dependent decline in subsequent ACTH-stimulated cortisol secretion. In the absence of a preincubation, neither compound affected cortisol production, indicating the need for production of an active metabolite. When the 17 alpha-hydroxylase inhibitor, SU-10'603, was included during the preincubation period, neither SL nor 7 alpha-thio-SL decreased cortisol secretion, indicating the involvement of the 17 alpha-hydroxylase in the activation of both compounds. By contrast, neither the 11 beta-hydroxylase inhibitor, metyrapone, nor the cholesterol sidechain cleavage inhibitor, aminoglutethimide, diminished the effects of SL or of 7 alpha-thio-SL on cortisol secretion. Preincubation of cells with SL or 7 alpha-thio-SL also decreased the conversion of exogenous progesterone to cortisol, but did not affect cortisol production from the 17 alpha-hydroxylated substrates, 17 alpha-hydroxyprogesterone and 11-deoxycortisol, suggesting that only 17 alpha-hydroxylation was impaired. In addition, there was a decline in 17 alpha-hydroxylase activity in microsomes isolated from cells preincubated with SL or with 7 alpha-thio-SL, but no change in microsomal 21-hydroxylase or in mitochondrial 11 beta-hydroxylase and cholesterol sidechain cleavage activities. The results indicate that the direct effects of SL and of 7 alpha-thio-SL on the adrenal cortex to decrease cortisol production result from the selective inhibition of 17 alpha-hydroxylation. Since 17 alpha-hydroxylase activity is apparently required for the activation of both compounds, suicide inhibition of the enzyme may be the mechanism of action.

Prophylactic antibiotics in elective orthopedic surgery: a prospective study of 1,591 cases.

A double-blind prospective study involving 1,591 clean orthopedic surgical procedures was done to test the effectiveness of preoperative and intraoperative antibiotics in reducing the postoperative infection rate. The antibiotic and placebo groups were analyzed carefully for factors known to predispose to infection. Several minor exceptions were noted, but generally the antibiotic and placebo groups were comparable with regard to these factors. A decrease in overall postoperative infection rate from 5.0% in the placebo group to 2.8% in the antibiotic group was found. In specific areas such as the hip and spine a much greater reduction in postoperative wound infections occurred than in the group as a whole.