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Biomedical subjects

G Phillipou

Publications and source records attributed to G Phillipou.

At least 37 records · Page 2Linked to original sources
PubMed1989

Screening for microalbuminuria by use of a rapid, low-cost colorimetric assay.

We evaluated the pyrogallol red-molybdate(IV) method for quantification of urinary protein as a screening procedure for microalbuminuria by determining the assay's sensitivity and specificity at different concentrations of urinary albumin as measured by a comparison laser-nephelometric immunoassay. The pyrogallol red-molybdate(IV) method has sensitivity and specificity similar to that for other semiquantitative assays, but it is less expensive and sample throughput can be high if microtiter plate techniques are used.

Albuminuria↗
PubMed1988

Urinary 5 alpha-androstane-3 alpha,17 beta-diol levels in normal and hirsute women: discriminating power and relation to other urinary steroids.

The urinary levels of seven steroids, 5 alpha-androstane-3 alpha,17 beta-diol, 5 beta-androstane-3 alpha,17 beta-diol, androsterone, etiocholanolone, tetrahydrocortisone, tetrahydrocortisol and allotetrahydrocortisol were measured in both normal (n = 18) and hirsute (n = 24) women. The results confirmed 5 alpha-androstane-3 alpha,17 beta-diol as the most significant steroid with respect to discrimination between hirsute and normal subjects. Investigation of the inter-steroid relationships, using multivariate techniques established that the mode of steroid metabolism was different between the two groups. Whereas in normal women the strong correlation amongst all the androgen metabolites inferred a predominant hepatic route to 5 alpha-androstane-3 alpha,17 beta-diol formation, the same analogy was not applicable to the hirsute subjects. Excellent agreement was found for the predicted vs actual excretion of 5 alpha-androstane-3 alpha,17 beta-diol in normal women, based on a regression model involving the six other steroids as independent variables. When the same model was used for estimation of 5 alpha-androstane-3 alpha,17 beta-diol levels in thirteen hirsute subjects, misclassified as "normal", 50% gave values which were considerably less than actually measured. It is suggested that this discrepancy, with respect to these hirsute subjects is a reflection of extrahepatic production of 5 alpha-androstane-3 alpha,17 beta-diol due to increased 5 alpha-reductase activity.

Adult↗
PubMed1988

Re-evaluation of the fructosamine reaction.

The difference in spectral characteristics between 1-deoxy-1-morpholinofructose (DMF) and protein/plasma samples in the fructosamine reaction has been related to the solubility of the diformazan formed by reduction of nitro blue tetrazolium chloride. Addition of the surfactant Triton X-100 (20 g/L) to the reagent buffer not only corrects this anomaly but also enhances the absolute response. Detailed investigation of DMF and dihydroxyacetone as calibration standards for the reaction established a clear preference for the latter. Fundamental differences in reaction kinetics were also noted between the Amadori rearrangement products of glucose formed from morpholine (DMF) or the amino lysine groups of protein (glycated albumin). From the reactivity of dihydroxyacetone, as well as glyceraldehyde, observed in the fructosamine reaction, and the presence of this class of compounds (trioses) in human plasma, we infer that they may also contribute to the differentiation of diabetic and non-diabetic samples.

Fructosamine↗
PubMed1987

Quantification of 5 alpha- and 5 beta-androstanediols in urine by gas chromatography-mass spectrometry.

We measured concentrations of 5 alpha-androstane-3 alpha,17 beta-diol (Ad) and 5 beta-androstane-3 alpha,17 beta-diol (beta-Ad) in urine by specific capillary gas chromatography-mass spectrometry, with [16,16,17 alpha-2H3]-5 alpha-androstane-3 alpha,17 beta-diol as the internal standard. Comparison of the so-derived reference intervals for Ad and beta-Ad in men and women with those previously published indicates a significant positive bias for many of the previous assays in comparison with our procedure. Both Ad and beta-Ad have a pronounced diurnal rhythm, with maximum excretion in the interval 2300-0700 hours. Concentrations of Ad and beta-Ad were significantly correlated (r = 0.786, p less than 0.001), but the ratio of Ad to beta-Ad was not correlated to that for androsterone to etiocholanolone, the major 5 alpha and 5 beta metabolites of androgens in urine.

Adult↗
PubMed1985

15-Hydroxycyproterone acetate and cyproterone acetate levels in plasma and urine.

15 beta-Hydroxycyproterone acetate (15HOCPA) and cyproterone acetate (CPA) have been quantitated in human plasma and urine by a selective high-performance liquid chromatographic assay. The levels of 15HOCPA in plasma are generally twice those of its precursor CPA, although both compounds appear to have similar clearance rates. Approximately 6% of the dose is excreted into the urine, predominantly (greater than 90%) as the free form of 15HOCPA and CPA.

Chromatography, High Pressure Liquid↗
PubMed1985

Deuterium labelled steroid hormones: tracers for the measurement of androgen plasma clearance rates in women.

A method employing stable isotope-labelled tracers and gas chromatograph-mass spectrometry (GC-MS) analysis has been used to measure the plasma clearance rates (PCR's) of androstenedione (A) and testosterone (T) in normal women and women with androgen abnormalities including hirsutism and polycystic ovary syndrome. A solution of deuterium-labelled A and T is infused at a constant rate and blood samples taken at 2 and 2.25 h. Solvent extracts of the derived plasma samples, to which an internal standard has been added, are derivatized with pentafluoropropionic anhydride and the endogenous steroid and deuterated steroid are quantitated after an injection of the derivatization mixture into a capillary column GC-MS. The concentration of the deuterated steroid in the infusion mixture is measured and the PCR is calculated. In premenopausal normal women the PCRA is 1950 +/- 184 1/24 h (n = 5) and the PCRT is 484 +/- 82 1/24 h (n = 7).

Androgens↗
PubMed1985

A new defect in the peripheral conversion of cortisone to cortisol.

A steroid disorder is described in two sisters, aged 13 and 17 years, in which the metabolism of cortisol results almost exclusively in urinary excretion of tetrahydro-cortisone (11-keto) derivatives. The evidence implies the existence of a deficiency in the peripheral enzymatic conversion of cortisone to cortisol.

Adolescent↗
PubMed1985

Evidence for a hypothalamic site of action of clomiphene citrate in women.

To examine the site of action of clomiphene citrate (CC), LH and FSH pulsatile amplitude, frequency, and responsiveness to GnRH (10 micrograms, iv) were studied in 11 women during the early follicular phase of the menstrual cycle. Six women received CC (150 mg/day) on cycle days 2, 3, and 4, while 5 women received placebo tablets. Blood samples were drawn at 10-min intervals for 8 h before and after the treatment regimen on cycle days 2 and 5, respectively. All women treated with CC had multiple follicular development, as determined by ultrasound. Peripheral levels of estradiol did not change after CC treatment, while progesterone levels decreased slightly. Mean levels of LH increased from 7.5 +/- 0.9 (+/- SEM) to 10.7 +/- 1.4 mIU/ml (P less than 0.05), and FSH increased from 6.7 +/- 0.9 to 10.1 +/- 0.9 mIU/ml (P less than 0.01). After exposure to CC, the pulse frequency of LH during an 8-h period increased significantly (3.3 +/- 0.7 on day 2 vs. 6.8 +/- 0.8 on day 5; P less than 0.01), while the pulse frequency of FSH increased from 3.8 +/- 0.6 to 5 +/- 1.4, as determined by computer pulse analyses. The pulse amplitude of LH and FSH was not significantly altered. In the placebo-treated group, neither pulse amplitude nor pulse frequency changed significantly between cycle days 2 and 5. Pituitary sensitivity to exogenous GnRH did not change after CC treatment. Since the pulsatile frequency of LH is governed by hypothalamic influences, these findings provide compelling evidence for a hypothalamic site of action for CC, probably by inducing an increase in the frequency of GnRH secretion.

Adult↗
PubMed1984

Evaluation of a commercial radioassay for the simultaneous estimation of vitamin B12 and folate, with subsequent derivation of the normal reference range.

A commercial assay kit method for the simultaneous estimation of vitamin B12 and folate concentrations has been evaluated. Values derived for folate by a microbiological assay and vitamin B12 by a verified radioassay showed good correlation with the investigated method. The clinical sensitivity of the assay for detecting deficient concentrations of vitamin B12 and folate was comparable to that of the non-commercial methods and other more definitive clinical procedures. Establishment of reference ranges, based on accepted statistical criteria, are discussed and such ranges are contrasted with those proposed by the manufacturer. The kit method is time and labour saving compared with the non-commercial methods.

Adult↗
PubMed1983

Special uses of a gas chromatograph-mass spectrometer in endocrinology.

Based on the isotope dilution principle, and using deuterium-labelled steroids as tracers combined with GC-MS analysis, clinically acceptable procedures for the measurement of daily urinary production rates (UPR's) and metabolic clearance rates (MCR's), of hormonal steroids, have been developed. In clinical tests, using progesterone and androstenedione as models the UPR's and MCR's obtained compared favourably with values obtained using radioisotope-labelled tracers. The heavy isotope procedure proved, however, to be superior to the radioisotope methods in accuracy, speed and patient safety.

Androstenedione↗
PubMed1983

Applications of heavy isotope tracers to clinical studies: progesterone urinary production rate determination in the menstrual cycle and pregnancy.

A method for the in vivo determination of progesterone production rate using progesterone labeled with deuterium as the tracer and gas chromatography-mass spectrometry for assessing isotope dilution in a urinary metabolite is described. By measuring the ratio of labeled to unlabeled free progesterone in a 24-h urine sample, the problem of identifying a unique metabolite appears to have been avoided. Median progesterone production rates on day 7 of the follicular phase and day 7 of the luteal phase were 3.5 mumol/24 h and 72.6 mumol/24 h, respectively. Where repeated determinations were performed through the luteal phase in two nonconceptual cycles, the familiar midluteal plateau of progesterone production was noted. The MCR of progesterone calculated from luteal phase data was 2051 1/24 h (SD, 275 1/24 h). When determined in pregnancy, progesterone production varied from 250 mumol/24 h at 6 weeks in a singleton pregnancy, to 1565 mumol/24 h at 35 weeks in a triplet pregnancy. Repeated determinations before term in a twin pregnancy detected no evidence of decreasing progesterone production before labor. The value of urinary pregnanediol and plasma progesterone to indirectly monitor progesterone production were confirmed.

Adult↗
PubMed1982

Urinary 6-sulphatoxy melatonin excretion during the human menstural cycle.

The excretion of 6-sulphatoxy melatonin in urine has been shown to provide a reliable index of melatonin production in man. Daily measurements made in two healthy ovulating women showed that both the total amount excreted/day and the proportion excreted during the sleep period remained relatively constant for each subject throughout the menstrual cycle. These data do not support the view that there are changes in melatonin production which correlate with cyclical reproductive endocrine function in the human.

Adult↗
PubMed1982

Investigation of urinary steroid profiles as a diagnostic method in Cushing's syndrome.

Patients with Cushing's syndrome may be discriminated from normal subjects on the basis of their respective neutral urinary steroid profile. In the former group, evidence is presented that lowered levels of T3 secondary to hypercortisolism, decrease the liver enzymes associated with 5 alpha-reductase and 11 beta-hydroxy steroid dehydrogenase activity. As a result the metabolism of cortisol and androstenedione in Cushing's syndrome yields a unique pattern dominated by 5 beta and 11 beta-hydroxy steroid metabolites.

Adolescent↗
PubMed1981

High-performance liquid chromatographic determination of clomiphene using post-column on-line photolysis and fluorescence detection.

A method has been developed for the extraction and quantitation of the ovulatory stimulant drug clomiphene from plasma. The cis- and trans-isomers were separated by normal-phase chromatography using chloroform-methanol as the mobile phase. After eluting from the column, the clomiphene was passed through a PTFE photolysis coil irradiated by a powerful UV lamp, resulting in conversion of the isomers to highly fluorescent species. The derivatised material was then detected using a fluorescence spectrometer. Use of this method enables a substantial improvement of sensitivity over UV detection and has permitted the measurement of plasma clomiphene levels in patients receiving clomiphene therapy.

Automation↗