1,720,963 research outputs found
Separation methods for acyclovir and related antiviral compounds
No full textAcyclovir (ACV) is an antiviral drug, which selectively inhibits replication of members of the herpes group of DNA
viruses with low cell toxicity. Valaciclovir (VACV), a prodrug of ACV is usually preferred in the oral treatment of viral
infections, mainly herpes simplex virus (HSV). Also other analogues such as ganciclovir and penciclovir are discussed here.
The former acts against cytomegalovirus (CMV) in general and the latter against CMV retinitis. The action mechanism of
these antiviral drugs is presented briefly here, mainly via phosphorylation and inhibition of the viral DNA polymerase. The
therapeutic use and the pharmacokinetics are also outlined. The measurement of the concentration of acyclovir and related
compounds in biological samples poses a particularly significant challenge because these drugs tend to be structurally similar
to endogenous substances. The analysis requires the use of highly selective analytical techniques and chromatography
methods are a first choice to determine drug content in pharmaceuticals and to measure them in body fluids. Chromatography
can be considered the procedure of choice for the bio-analysis of this class of antiviral compounds, as this methodology is
characterised by good specificity and accuracy and it is particularly useful when metabolites need to be monitored. Among
chromatographic techniques, the reversed-phase (RP) HPLC is widely used for the analysis. C Silica columns from 7.5 to 18
30 cm in length are used, the separation is carried out mainly at room temperature and less than 10 min is sufficient for the
analysis at 1.0–1.5 ml/min of flow-rate. The separation methods require an isocratic system, and various authors have
proposed a variety of mobile phases. The detection requires absorbance or fluorescence measurements carried out at
250–254 nm and at l 5260–285 nm, l 5375–380 nm, respectively. The detection limit is about 0.3–10 ng/ml but the ex em
most important aspect is related to the sample treatment, mainly when body fluids are under examination. The plasma
samples obtained from human blood are pre-treated with an acid or acetonitrile deproteinization and the supernatant after
centrifugation is successively extracted before RP-HPLC injection. Capillary Electrophoresis methods are also discussed.
This new analytical approach might be the expected evolution, in fact the analyses are improved with regard to time and
performance, in particular coated capillary as well as addition of stabilisers have been employed. The time of analysis is
shortened arriving at less than half a minute. Furthermore by using an electrochemical detection, and having a calibration
linearity in the range of 0.2–20.0 ng/ ml, the detection limit is 0.15 mg/ ml. The measurements of acyclovir and penciclovir
have been presented but in the future other related drugs will probably be available using CE methods
Urine cortisol and cortisone and water intake in athletes
No full textAIM: The aim of this study was to investigate the urine cortisol (F) and cortisone (E) relation, having a well-defined water intake.
METHODS: Urine specimens were collected from 10 male trained cyclists (19+/-1 year, 70+/-4 kg, 179+/-4 cm), at rest just before the test (pre-exe) and until 45 min after the cycle ergometer exercise test (45 min at 50-60% VO2max) (post-exe) in the morning. This investigation measured the diuresis in the pre-exe and post-exe after each athlete had drunk 1 L of water from waking-up, after bladder emptying, to the start of the test (pre-exe) and 1 L during the 45 min after the exercise (post-exe).
RESULTS: Urinary F and E concentrations demonstrated a significant decrease comparing pre-exe with post-exe (177+/-134 vs 64+/-21 and 706+/-475 vs 372+/-178 nmol.L(-1) respectively, p < 0.05). This significant decrease was verified when diuresis and urinary creatinine were taken into account and the ratio measured.
CONCLUSION: One litre of water intake after exercise seemed to have no effect on urine F and E excretion. Moreover the urine F/E ratio was not statistically different comparing pre-exe with post-exe
Cortisol assays and diagnostic laboratory procedures in human biological fluids.
No full textThe overview of cortisol physiology, action and pathology is achieved in relation to the hypothalamic-pituitary-adrenal axis alteration by laboratory investigation. The measurements of cortisol and related compound levels in blood, urine and saliva used to study the physiological and pathological cortisol involvement, are critically reviewed. The immunoassay and chromatographic methods for cortisol measurement in the various biological fluids are examined in relation to their analytical performances, reference ranges and diagnostic specificity and sensitivity. Moreover, blood, urine and saliva cortisol level measurements are described taking into account the diagnostic implications. The deduction is that each method requires the definition of its own reference range and its related diagnostic cut-off levels. Thus, this review, stressing the analysis procedures, could help to understand and compare the results of the different assay
Human saliva cortisone and cortisol simultaneous analysis using reverse phase HPLC technique
No full textMeasurement of free IGF-I saliva levels: perspectives in the detection of GH/IGF axis in athletes.
No full textEffects of two different types of exercise on GH/IGF axis in athletes. Is the free/total IGF-I ratio a new investigative approach?
No full textBACKGROUND: Human growth hormone (hGH) responds to bouts of exercise by increasing, while the insulin-like growth factor-I (IGF-I) responses are conflicting.
METHODS: Twenty well-trained male cyclists completed a brief duration exercise (A: warm up+increasing workload until exhaustion, lasting 25 min) and a medium duration exercise (B: warm up+70-80%VO(2 max)+increasing workload until exhaustion, lasting 40 min). The immunoreactivity of plasma hGH, the IGF-I in its total and free fraction were measured before and at the end of the exercise, and the free/total IGF-I ratio response to the two cycling exercise bouts was examined.
RESULTS: Both A and B demonstrated increased hGH (from 77+/-122 to 544+/-327 and 28+/-68 to 369+/-276 pmol/l respectively) and total IGF-I (from 67+/-10 to 70+/-10 and 55+/-14 to 61+/-15 nmol/l respectively). The free IGF-I was decreased only in A (from 0.38+/-0.16 to 0.32+/-0.14 nmol/l). Both A and B demonstrated a decreased free/total IGF-I ratio (from 0.57+/-0.30 to 0.46+/-0.22 and 0.61+/-0.37 to 0.52+/-0.29).
CONCLUSION: Brief and medium duration physical exercise influences the hGH, the total and free IGF-I concentrations. The free/total IGF-I ratio was also influenced and it might be related to the GH/IGF system. Its investigation might be a way of studying the training conditio
N-terminal pro C-type natriuretric peptide relation with prolactin in the elderly
No full textA relationship between natriuretic peptides, reproduction, and the elderly has been known for some time. To investigate the relation between Nt-pro C-type natriuretic peptide (CNP) and reproduction, a group of 71 elderly men and women were studied. In particular, the relation between prolactin (PRL) and Nt-proCNP was examined. Nt-proBNP (N-terminal Brain NP), pro Atrial (ANP)(1-98) (Atrial NP), Nt-proCNP, luteinizing and follicle-stimulating hormones, PRL, progesterone, and 17β-estradiol were measured in 51 (23 males/28 females) hypertensive patients. A total of 20 normotensive elderly subjects formed the control group. The hypertensive patients (TH) were divided into subgroups, accordingly to their main other clinical diagnosis, namely Diabetes, Hypertension, Peripheral Arterial Occlusive Disease. A direct correlation was observed between Nt-proCNP and PRL in all subjects, patients, and healthy volunteers (r = 0.56; P < 0.001). An inverse correlation between Nt-proCNP and follicle-stimulating hormones was observed in TH patients (r = -0.55; P < 0.05). proANP(1-98) and Nt-proBNP correlated with PRL respectively in peripheral arterial occlusive disease (r = 0.57; P < 0.05) and in TH (r = 0.52; P < 0.05). A direct correlation was found between the latter and luteinizing hormone in Diabetes (r = 0.64; P < 0.05). We demonstrate, for the first time, a correlation between Nt-proCNP and PRL in sick and healthy elderly subjects. Also proANP(1-98) and Nt-proBNP appeared to coregulated with PR
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
