Chris Salonikas

Improved method for plasma malondialdehyde measurement by high-performance liquid chromatography using methyl malondialdehyde as an internal standard

Measurement of malondialdehyde (MDA) is an important contribution to the assessment of oxidative stress. We report a sensitive and reproducible high-performance liquid chromatography (HPLC) method for measurement of plasma MDA in the assessment of lipid peroxidation. Using methyl malondialdehyde (Me-MDA) as an internal standard with reversed-phase HPLC and UV detection and derivatisation with 2,4 dinitrophenylhydrazine (DNPH), we obtained maximum MDA values with 60-min incubation of 10% plasma with 1 M NaOH at 60 degrees C. The dilution of the plasma and a longer incubation time in the alkaline hydrolysis step greatly improved recovery of MDA from its bound form. Ratios of peak height of MDA/Me-MDA were linear over a range of 0-100 microM with correlation coefficients >0.99. The recovery was 88.5%. Within and between run variations were <4 and <7%, respectively. The mean MDA value measured in 20 healthy volunteers was 13.8 microM (+/-1.32).

Relationship of homocysteine, folic acid and vitamin B12 with depression in a middle-aged community sample.

BACKGROUND Case control studies have supported a relationship between low folic acid and vitamin B112 and high homocysteine levels as possible predictors of depression. The results from epidemiological studies are mixed and largely from elderly populations. METHOD A random subsample of 412 persons aged 60-64 years from a larger community sample underwent psychiatric and physical assessments, and brain MRI scans. Subjects were assessed using the PRIME-MD Patient Health Questionnaire for syndromal depression and severity of depressive symptoms. Blood measures included serum folic acid, vitamin B12, homocysteine and creatinine levels, and total antioxidant capacity. MRI scans were quantified for brain atrophy, subcortical atrophy, and periventricular and deep white-matter hyperintensity on T2-weighted imaging. RESULTS Being in the lowest quartile of homocysteine was associated with fewer depressive symptoms, after adjusting for sex, physical health, smoking, creatinine, folic acid and B12 levels. Being in the lowest quartile of folic acid was associated with increased depressive symptoms, after adjusting for confounding factors, but adjustment for homocysteine reduced the incidence rate ratio for folic acid to a marginal level. Vitamin B12 levels did not have a significant association with depressive symptoms. While white-matter hyperintensities had significant correlations with both homocysteine and depressive symptoms, the brain measures and total antioxidant capacity did not emerge as significant mediating variables. CONCLUSIONS Low folic acid and high homocysteine, but not low vitamin B12 levels, are correlates of depressive symptoms in community-dwelling middle-aged individuals. The effects of folic acid and homocysteine are overlapping but distinct.

Pharmacokinetics of Ciprofloxacin in the Human Eye: a Clinical Study and Population Pharmacokinetic Analysis

ABSTRACT Ciprofloxacin, a fluoroquinolone antibiotic active against a wide variety of bacteria, is one of a few antibiotics which enters the human eye after oral administration. However, little is known about its pharmacokinetics in the human eye. One or two oral doses of 750 mg of ciprofloxacin (at a 12-h interval) were administered to 48 patients at various times prior to ocular surgery. Clotted blood, aqueous, and vitreous were collected at surgery, and the concentrations of ciprofloxacin were assayed by high-performance liquid chromatography. Our data were combined with those of others, and a population pharmacokinetic analysis was conducted. The concentrations of ciprofloxacin in both aqueous and vitreous were lower than those in serum and peaked at a later time. The pharmacokinetics of ciprofloxacin in aqueous and vitreous were fitted to a compartmental model in which the antibiotic was transferred into and out of the two compartments (aqueous and vitreous) by first-order processes. Population pharmacokinetic software, P-Pharm, was used to calculate the mean half-lives of the loss of ciprofloxacin from aqueous and vitreous, which were 3.5 and 5.3 h, respectively. At steady state, the mean ratios of then concentrations in aqueous and vitreous to the concentrations in serum were 23 and 17%, respectively. After the administration of one or two doses of 750 mg of ciprofloxacin, the concentrations in both aqueous and vitreous in a number of patients were lower than the MICs at which 90% of isolates are inhibited (0.5 mg/liter) for common intraocular bacterial pathogens. Simulations of concentrations in the eye after the administration of higher doses (1,500 mg of ciprofloxacin as a single dose, two doses of 750 mg 2 h apart, and 750 mg every 6 h) indicated that in approximately 20% of patients the concentrations would still be below 0.5 mg/liter. Although oral ciprofloxacin may be a beneficial adjunctive therapy, the use of oral ciprofloxacin alone may not be adequate for perioperative prophylaxis or for treatment of bacterial endophthalmitis.

Associations between plasma antioxidants and hypertension in a community-based sample of 415 Australians aged 60–64

It has been suggested that increased oxidative stress may be both a cause as well as a consequence of hypertension. In vivo oxidation of low-density lipoproteins by oxygen-free radicals may increase hypertension-related atherogenesis, and antioxidants may be beneficial in this regard. Previous findings concerning associations between serum measures of antioxidants and hypertension have however been inconsistent. Plasma levels of β-carotene, Vitamin A, E, uric acid, homocysteine and total antioxidant capacity, as well as two markers of oxidative stress, malondialdehyde (MDA) and protein carbonyls, were measured in morning fasting blood samples provided by 415 Australians aged 60–64 years, selected randomly from the community. Participants also provided information on sociodemographic attributes, mental and physical health, and provided two measures of resting blood pressure, allowing a diagnosis of definite or borderline hypertension. Those with hypertension had lower levels of β-carotene and higher levels of uric acid and MDA compared to normotensive participants. The last two of these associations persisted when the analyses controlled for lifestyle and health factors. The findings from this study offer limited support for the proposition that lower antioxidant status and higher oxidative stress are associated with hypertension, and suggest the need for longitudinal studies to examine causality and intervention studies to determine the benefit of antioxidants in this group.

Vitamin K in preterm breastmilk with maternal supplementation

Six healthy lactating mothers who gave birth to preterm infants at a median post conceptional age of 29.5 (range 26‐30) weeks were given 2.5 mg phylloquinone (vitamin K1) orally daily for 2 weeks beginning at a median postconceptional age of 31.5 (range 28–32) weeks. Phylloquinone was measured in the breastmilk daily for 14 d. Trough plasma phylloquinone concentrations were also determined on four occasions. Phylloquinone levels in the breastmilk increased from a baseline of 3 ± 2.3ngml‐1 to 22.6 ± 16.3 ng ml‐1 (mean ± SD) after the first dose (p < 0:05); a gradual increase was noted until phylloquinone levels reached a plateau of 64.2 ± 31.4ng ml‐1 after the sixth daily dose.

Antioxidant levels in peripheral blood, disease activity and fibrotic stage in chronic hepatitis C.

Background: This study addressed the suggested association between levels of the antioxidants glutathione (GSH), vitamin C and vitamin E in peripheral blood and the histological activity and fibrosis stage in chronic hepatitis C (CHC). We then determined whether regular antioxidant supplementation influenced these antioxidant levels or disease severity.

Neonatal plasma vitamin K1 levels following oral and intramuscular administration of vitamin K1

Vitamin K1 levels were measured by high performance liquid chromatography in cord blood (n= 33) and at the age of 97–120 h after administration of 2 mg of vitamin Kl orally (n= 88) or 1 mg of vitamin K1 by im injection (n= 88). Vitamin K1 levels were less than 0.05 μg/l in cord blood. The mean (range), SEM, mode and median values (μg/l) for the infants given oral vitamin K1 were 17.99 (1–56), 1.25, 8 and 15.5 and those for the infants given im vitamin Kl 15.83(2–57), 1.01, 11and 14, respectively. The t‐test showed no significant difference in the mean values (p= 0.09) in the infants given oral or im vitamin K.

The comparative pharmacokinetics of modified-release and immediate-release paracetamol in a simulated overdose model.

Background:  Panadol Extend (PEx) is an over‐the‐counter, modified‐release formulation of paracetamol. Each 665 mg tablet contains 69% slow‐release and 31% immediate‐release paracetamol. In simulated human overdose, PEx exhibits lower and later peak serum concentrations and a lower area‐under‐the‐curve (AUC) than comparable doses of immediate‐release paracetamol (APAP‐IR). The lower AUC might result from incomplete absorption of paracetamol or simultaneous metabolism with absorption.