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Biomedical subjects

M Candito

Publications and source records attributed to M Candito.

66 records · Page 4Linked to original sources
PubMedDate not supplied

[Plasma homocysteine measurement: a study of pre-analytical variation factors for conditions for total plasma homocysteine concentration].

An increase in homocysteine, a sulphur amino acid, is nowdays considered as a risk factor for cardiovascular diseases, and is independent of other risk factors. Reference range for total plasma homocysteine level in adults is usually 5-15 mmol/l. Hyperhomocysteinemia is defined as a fasting total plasma homocysteine level > 15 mmol/l. There may be also graded increased risks for subjects with homocysteinemia from 10 to 15 mmol/l. However, no threshold has been defined, partly because of the lack of standardization in pre-analytical and analytical steps. The aim of the present work was to evaluate three pre-analytical parameters on plasma homocysteine levels: i) the influence of three anticoagulants (EDTA, sodium citrate and lithium heparin); ii) the delay period of blood sample on ice before centrifugation; and iii) the advantages of strong acidic citrate at room temperature. The mean concentrations of total plasma homocysteine were different in function of the anticoagulant. These differences (EDTA minus lithium heparin or EDTA minus sodium citrate) were less than 10% however the used methods and could explain the good correlation between the results. However we recommend to keep the anticoagulant constant in the same study. When EDTA blood samples were immediately put on crushed ice, the maximum delay period before centrifugation could reach 4 hours. If ice is unavailable, strong acidic citrate at room temperature is a good alternative until for 4 hours.

Anticoagulants↗
PubMedDate not supplied

[Biochemical diagnosis of pheochromocytoma and neuroblastomas].

Pheochromocytoma and neuroblastoma are distinct tumours, but their biological diagnosis is based on secretion increase of one or several catecholamines. Assays have to be very sensible and specific for an early diagnosis. 24 hours urinary catecholamines and metabolites are currently measured, but technical improvements permit plasma metanephrine assay, an excellent indicator of pheochromocytoma. HPLC coupled to electrochemical detection represents the most efficient methodology. After a review of urinary and plasma assay methods, the authors show usual values of catecholamines, metanephrines, HVA and VMA, according to ages, and give examples of results encountered in classical or not tumours and in falsely positive cases. Urinary metanephrine assay is the most sensible and specific in biological diagnosis of pheochromocytoma, while catecholamines and VMA assays lack of sensibility. Results have to be given by 24 hours and by creatinine ratio. Metanephrine assay can be performed also in plasma and exhibits the same interest. However, in urine as in plasma, in case of renal failure, results cannot be interpreted. Neuroblastoma biological diagnosis is based classically on HVA, VMA, and dopamine assays, nowadays only in 24 hours urine (or in urinary micturition for screening), and results are also expressed as creatinine ratio. But even if several assays are advisable, 5% of the neuroblastoma cases do not produce increased catecholamine values. In some cases, metanephrine assay could be of interest. After the age of 12 months, clinical expression of neuroblastoma is dramatic in 70% of cases. So, a biological screening has been experimented in several countries including France. A French translation of the consensus conference report (1998) is appended, which shows the complexity of neuroblastoma screening. Now, there is no evidence that early tumour detection by screening lessens the mortality rate, but a weak benefit is not excluded.

Adolescent↗
PubMedDate not supplied

[Comparison of plasma total homocysteine determinations in 9 French hospital laboratories by using 6 different methods].

A lot of methods are now available for total plasma homocysteine (tHcy) determination. Commercial kits using immunoassay, easier to use, begin to supplant in-house laboratory methods. Our aim is to evaluate the interchangeability of tHcy measurements in 9 French hospital laboratories. Six different method types were used: 2 gas chromatography-mass spectrometry (GC-MS), 2 HPLC with fluorescence detection subdivided in one in-house method and one commercial kit (Bio-Rad ), 3 fluorescence polarization immunoassays (FPIA), 1 enzyme immunoassay, 1 amino acid analyser, 1 capillary electrophoresis coupled with laser-induced fluorescence detection (EC-LIF). Each laboratory analysed 41 patient's plasma samples in which 8 samples contained added homocystine. Results were analysed for imprecision, recovery, and methodological differences. The mean among-laboratory imprecision (CV) ranged from 12.5 to 18% in function of plasma sample type and was identical to the mean among-method variation. In terms of recovery, we obtained underestimated results with immunoassays. The bias relative to the GC-MS method was less than 12.5% except for two laboratories, one using FPIA assay and the other EC-LIF. In conclusion, the interchangeability of tHcy results between laboratories is not satisfactory and does not allow us to evaluate cardiovascular risk linked to moderate increases of tHcy.

Blood Chemical Analysis↗
PubMedDate not supplied

[Neural tube defects and vitamin B12: a report of three cases].

Periconceptional folic acid supplementation reduces the frequency of embryological neural tube defects (NTD). This fact led the USA to fortify grain products with folic acid (140 microg/100 g) starting in January 1998, with a resultant decrease in the incidence of NTD. Folate deficiency is thus confirmed to be a risk factor for NTD. However, in a prospective study, we investigated three women who conceived a fetus with NTD; no folate deficiency was found in these women but all three had decreased vitamin B12 levels (cobalamin), which can be an other risk factor. Samples were obtained from two women in Algeria, 2 days after interruption of pregnancy, and from a vegetarian woman, in France, one month after interruption of pregnancy. Red cell folate and plasma folate, vitamin B12, B6 and homocysteine were assayed and the mutations C677T (in metylenetetrahydrofolate reductase gene), A2756G (in methionine synthase gene) and A66G (in methionine synthase reductase gene) were sought. Elevated plasma folate levels were found in both Algerian women. Vitamin B 12 levels in all three women were decreased or in the lowest quartile of normal values. One woman presented simultaneously a vitamin B 12 deficiency, and heterozygous mutations in the three genes. The second woman presented a A66G homozygous mutation and the third heterozygous C677T and A66G mutations. Acquired and inborn factors are intricated in some cases of pregnancies with NTD and B 12 deficiency can be responsible for intracellular folate cycle failure. It would therefore be advisable to consider fortifying grain products with both folic acid and vitamin B12.

Adult↗
PubMedDate not supplied

[Circadian rhythm of plasma norepinephrine in depressive disorders. Preliminary study].

The biological desynchronisation hypothesis of (endogenous) depressive disorders arises from the disturbances in the circadian rhythmicity of several biological functions in depressive illness and clinical improvement during various sleep deprivation processes. Furthermore, supportive evidence exists to postulate a central noradrenergic dysfunction, at least in a sub group of depressive disorders. We studied the 24 h kinetics of plasma norepinephrine in patients suffering from Affective Disorders-Major Depressive Episode according to DSM III criteria. Blood samples were drawn hourly from an indwelling venous catheter in supine subjects. Plasma NE was measured by HPLC with electrochemical detection. 5 patients (age: 35-63) were studied in base line drug free depressive state and compared with 5 control subjects (age: 44-53), then, in 4 patients, on the 8th and 21st days under antidepressant treatment. Control subjects exhibited a circadian rhythm of TP but a weak amplitude and low values during sleep, as previously described. Depressed patients did not display any rhythmicity because of a reduced amplitude and high plasma levels during sleep. Antidepressants did not restore the rhythm. Our results suggest a rhythmic instability involving a circadian lability linked to an ultradian release during sleep. This NA disinhibition could participate in the depressive desynchronisation and the potential relationships with sleep disorders must be discussed.

Adult↗
PubMedDate not supplied

[Principle methods of determining plasma 3-methoxy-4-hydroxyphenyl glycol].

The dosage of plasma 3-methoxy-4-hydroxyphényl glycol (MHPG) presents a great interest, specially in psychiatry. Several methods are described: gas chromatography, with or without mass spectrometry, high performance liquid chromatography with some internal standard problems and with different modes of extractions and radioimmunoassay. Every method presents advantages but also inconveniences which are discussed.

Brain↗
PubMedDate not supplied

Type 1 diabetes mellitus and homocyst(e)ine.

High Homocyst(e)ine levels (H) have been recently recognized as a risk factor for atherosclerosis. Patients with Diabetes Mellitus (DM) are prone to atherosclerosis. Therefore, this study was designed to search for the effect of DM on H and their relationship. Forty-one Type 1 diabetic subjects (DS, age 34.8 +/- 12 yr, DM duration: 10.7 +/- 11.1 yr) were compared to 40 age-matched control subject (CS, age 34.2 +/- 9.1 yr). H (measured by ion-exchange chromatography, units: mumol/l) and several parameters (creatininemia; triglycerides; total, HDL, LDL cholesterol; Lp(a); HbA1c; vitamins B9 and B12) were determined after an overnight fast. H were significantly (p = 0.0001) lower in DS (6.8 +/- 2.2) than in CS (9.5 +/- 2.9). This difference was still apparent in male and female subgroups compared to matched CS (p = 0.003 for each). No correlation was found between H and: lipids, vitamins, renal or retinal status. But H seemed to increase with age, especially in women (p = 0.03; r = 0.32). While there is, at this time, no explanation for the lower H observed in DS, it appears that H cannot directly account for accelerated atherosclerosis in DM. Nevertheless, it remains to be established if high, or even normal, H could identify a subgroup of DS at higher risk of precocious and severe atherosclerosis.

Adult↗
PubMedDate not supplied

[Plasma tryptophan in a protein controlled diet in depressed patients].

Cerebral serotonin is synthetized from its blood precursor: tryptophan (TRP), an essential amino acid (6). TRP has been extensively studied since serotonine has been reported to be involved in the pathogenesis of depression (9). In one hand, brain serotonin content depends on regulation by plasma large neutral amino acids (LNAA): leucine, isoleucine, valine, tyrosine and phenylalanine that compete with TRP to cross over the blood brain barrier (7, 13). In the other hand TRP is largely linked with albumin. So, we have studied plasma total TRP, free TRP and the ratio TRP on LNAA as potential cerebral serotonin index. The aim of this study is to observe the blood variations of the biological parameters in fasting and postprandial conditions in 8 depressed women, aged from 57 to 78 years, on a short protein controlled diet: 4 women had TRP poor then rich diet and the others 4 rich then poor. Alimentary proteins modulated diets and each patient was his own control: the results under modulated diet were compared with those under normal diet at the same time. More over, 2 psychotic patients aged 58 and 70 years have been studied at the same time, in each group. Biological datas were compared with clinical evolution.

Aged↗