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Biomedical subjects

A Becerra

Publications and source records attributed to A Becerra.

12 recordsLinked to original sources
PubMed2000

Utility of fluorine-18-fluorodeoxyglucose positron emission tomography in differentiated thyroid carcinoma with negative radioiodine scans and elevated serum thyroglobulin levels.

BACKGROUND: This study aimed to determine the role of fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) in the follow-up of patients who underwent total thyroidectomy and iodine-131 ((131)I) ablation therapy for differentiated thyroid cancer and presented increased thyroglobulin levels with negative (131)I and thallium-201 ((201)Tl) scans. METHODS: Two patients with follicular carcinoma and eight with papillary tumors underwent total thyroidectomy and (131)I therapy until the (131)I scan was negative. (131)I and (201)Tl scans were performed with negative results in all cases, while serum thyroglobulin measurements were all positive with negative thyroglobulin autoantibodies. One week after the (131)I scans, all the patients underwent FDG-PET whole-body scans. RESULTS: The FDG-PET scan detected in 4 patients, a single focal increase of FDG uptake in one lymph node metastasis (subsequently confirmed histologically); in 1 patient, multiple pathological focal uptakes in brain, neck, and chest; and in 1 patient, two mild focal uptakes in the mediastinum, close to the tracheal branch. In 2 other patients, pathological FDG uptakes in cervical spine and mediastinum were not confirmed by other imaging techniques, and in the 2 remaining patients the scan results were inconclusive. The sensitivity of FDG-PET whole-body scan for detecting metastatic thyroid cancer was 60%. CONCLUSIONS: This study indicates that the FDG-PET whole-body scan is a useful tool in the follow-up of patients with differentiated thyroid cancer, negative (131)I and (201)Tl scans and elevated serum thyroglobulin levels. The FDG-PET scan detects metastatic disease in 60% of patients with differentiated thyroid cancer, enabling surgical therapy to be performed on accessible lesions.

Adenocarcinoma, Follicular↗
PubMed1999

Lipoprotein(a) and other lipoproteins in hypothyroid patients before and after thyroid replacement therapy.

AIMS: To analyse the influence of thyroid hormones on serum lipoprotein(a) (Lp(a)) concentration and other lipid parameters, and hence potentially on coronary artery disease (CAD) risk. METHODS: Thirty-six patients with hypothyroidism and 165 age-matched control euthyroid subjects were evaluated in a cross- sectional study, determining thyroid function tests and fasting serum lipids and lipoproteins. In a follow-up study for those hypothyroid patients the same determinations were repeated after normalization of thyroid state by levothyroxine (L-T(4)) replacement therapy. Patients needing other treatments were excluded. At baseline, patients with hypothyroidism had significantly higher levels of Lp(a), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), apolipoprotein (apo) A-I and apo B, and a higher TC/high-density lipoprotein cholesterol (HDL-C) ratio than control subjects. RESULTS: Severity of the hypothyroid state, expressed by serum thyroid-stimulating hormone, was correlated with serum levels of Lp(a), LDL-C, and TC (r= 0.64, 0.52, 0.49, P= 0.005, P= 0.033, P= 0. 048, respectively). The pretreatment Lp(a) levels were also correlated with those of posttreatment Lp(a)(r= 0.68, P= 0.002). All patients, who presented basal Lp(a) levels higher than 30 mg/dl, showed a decrease in Lp(a) concentrations by L-T(4)therapy, and these normalized in eight cases (22.2%). Euthyroid state gave rise to a significant reduction of serum Lp(a) by 32.3%, of LDL-C by 22. 8%, of TC by 17%, of apo A-I by 9.6%, and of apo B by 9.3%. After L-T(4)therapy, CAD risk, expressed as TC/HDL-C ratio, decreased by 19.9%. CONCLUSIONS: These results show that hypothyroidism is associated not only with elevated serum levels of LDL-C but also with elevated serum Lp(a) concentrations. Lp(a) levels may be at least partially modulated by thyroid hormone-dependent mechanisms, thus increasing the risk of developing premature atherosclerosis in hypothyroid state, that might be reduced by L-T(4)therapy.

Adult↗
PubMed1999

Comparative biochemistry of CO2 fixation and the evolution of autotrophy.

Carbon dioxide fixation is a polyphyletic trait that has evolved in widely separated prokaryotic branches. The three principal CO2-assimilation pathways are (i) the reductive pentose-phosphate cycle, i.e. the Calvin-Benson cycle; (ii) the reductive citric acid (or Arnon) cycle; and (iii) the net synthesis of acetyl-CoA from CO/CO2, or Wood pathway. Sequence analysis and the comparative biochemistry of these routes suggest that all of them were shaped to a considerable extent by the evolutionary recruitment of enzymes. Molecular phylogenetic trees show that the Calvin-Benson cycle was a relatively late development in the (eu)bacterial branch, suggesting that some form(s) of carbon assimilation may have been operative before chlorophyll-based photosynthesis. On the other hand, the ample phylogenetic distribution of both the Arnon and the Wood pathways does not allow us to infer which one of them is older. However, different lines of evidence, including experimental reports on the NiS/FeS-mediated C-C bond formation from CO and CH3SH are used here to argue that the first CO2-fixation route may have been a semi-enzymatic Wood-like pathway.

Acetyl Coenzyme A↗
PubMed1998

The role of gene duplication in the evolution of purine nucleotide salvage pathways.

Purine nucleotides are formed de novo by a widespread biochemical route that may be of monophyletic origin, or are synthesized from preformed purine bases and nucleosides through different salvage pathways. Three monophyletic sets of purine salvage enzymes, each of which catalyzes mechanistically similar reactions, can be identified: (a) adenine-, xanthine-, hypoxanthine- and guanine-phosphoribosyltransferases, which are all homologous among themselves, as well as to nucleoside phosphorylases; (b) adenine deaminase, adenosine deaminase, and adenosine monophophate deaminase; and (c) guanine reductase and inosine monophosphate dehydrogenase. These homologies support the idea that substrate specificity is the outcome of gene duplication, and that the purine nucleotide salvage pathways were assembled by a patchwork process that probably took place before the divergence of the three cell domains (Bacteria, Archaea, and Eucarya). Based on the ability of adenine PRTase to catalyze the condensation of PRPP with 4-aminoimidazole-5-carboxamide (AICA), a simpler scheme of purine nucleotide biosynthesis is presented. This hypothetical route requires the prior evolution of PRPP biosynthesis. Since it has been argued that PRPP, nucleosides, and nucleotides are susceptible to hydrolysis, they are very unlikely prebiotic compounds. If this is the case, it implies that many purine salvage pathways appeared only after the evolution of phosphorylated sugar biosynthetic pathways made ribosides available.

AMP Deaminase↗
PubMed1996

Direct determination of diuretic drugs in urine by capillary zone electrophoresis using fluorescence detection.

Four diuretic drugs banned in sport (amiloride, triamterene, bendroflumethiazide and bumetanide) have been separated by capillary zone electrophoresis (CZE) and detected using conventional fluorescence spectrometry. The effect of pH on electrophoretic parameters such as migration time, peak efficiency and peak height is discussed. Complete separation of the four drugs is achieved in less than 8 min at pH 8. No interference due to endogenous urine components is observed and thus direct urine analysis is feasible. Analytical figures of merit including precision and limits of detection are presented. Limits of detection range between 0.5 fmol for triamterene and 21.6 fmol for bumetanide.

Amiloride↗
PubMed1996

[Papillary tumor of the pancreas diagnosed by fine-needle aspiration].

We report the case of a 48 year-old woman with an epigastric palpable mass identified by abdominal echography and computed tomography as a solid pancreatic tumor. A cytology taken by fine needle aspiration guided by computed tomography was diagnostic of papillary pancreatic tumor, which was confirmed by surgical resection. We emphasize the low frequency and good prognosis of this type of tumor after surgical resection, and the utility of image techniques and fine needle aspiration to obtain a preoperative diagnosis.

Biopsy, Needle↗
PubMed1987

Noninvasive quantification of left ventricular myocardial mass by gated proton nuclear magnetic resonance imaging.

The validity of cardiac nuclear magnetic resonance imaging for determination of left ventricular myocardial mass was evaluated in nine dogs. A gated spin echo-pulsing sequence was used for in vivo imaging, obtaining 0.7 cm thick slices of the heart spaced by 1 cm. On each imaged slice, the left ventricular surface area was reproducibly determined by planimetry and was multiplied by slice spacing and specific gravity of the myocardium (1.05) to obtain slice mass. Total left ventricular mass was calculated by adding slice masses in short-axis (method I), transaxial (method II) and vertical long-axis (method III) orientations using Simpson's rule. With each method, masses of the portions of the left ventricle subject to partial volume effect either were not accounted for or alternatively were estimated from the same or an orthogonal imaging plane. Calculated left ventricular mass was compared with the actual excised left ventricular weight. With NMR imaging of in situ nonbeating hearts, best results were obtained when either method I or method II was used and partial volume effect was estimated either from the same or an orthogonal plane. With in vivo NMR imaging, best results were noted when method I was used and mass of the partial volume apex was calculated from transaxial slices: Y (in vivo NMR image) = 8.3 + 0.99X, r = 0.996, SEE = 3.14. For this method, the interobserver reliability coefficient and standard error of the measurement were 0.97 and 5.4, respectively. Compared with method I, in vivo methods II and III were associated with larger errors (SEE ranging from 13.03 to 19.03) regardless of the approach used to estimate partial volume effect. It is concluded that NMR imaging is a highly accurate noninvasive method for in vivo measurement of left ventricular mass in dogs and offers promise for accurate measurement of left ventricular mass in patients.

Animals↗
PubMedDate not supplied

A randomized cross-over study comparing cabergoline and quinagolide in the treatment of hyperprolactinemic patients.

Quinagolide (QUI) and cabergoline (CAB) are dopamine agonists recently introduced for the treatment of hyperprolactinemia. In the present study, these drugs have been compared in terms of effectiveness and tolerability. Twenty patients (18 females and 2 males) with hyperprolactinemia (8 with microprolactinomas, 6 with idiopathic hyperprolactinemia and 6 with empty sella turcica syndrome) were treated with oral QUI (75 microg once daily) and CAB (0,5 mg twice weekly), in a randomized cross-over trial with placebo between both drugs. Each drug was administered for 12 weeks, separated by other 12 weeks with placebo. PRL levels decreased with both drugs at 2 or 4 weeks of starting the treatment, without differences between both drugs at weeks 4, 8 and 12. At week 12, normal PRL levels (<20 ng/ml) were attained in 90% patients with CAB and only in 75% patients with QUI (p<0.05). After discontinuation of treatment, significant increase in serum PRL was higher after QUI withdrawal than after CAB. Clinical efficacy of both treatments was similar in terms of improvement amenorrhea, oligomenorrhea, galactorrhea, and impotence. All patients completed both cycles of treatment, and the most frequent side-effects were nausea, headache and dizziness, without significant differences between CAB (30%) and QUI (55%). Our study indicates that, at the doses employed here, CAB showed a high percentage of patients with normal PRL at the end of treatment and long-lasting efficacy in the levels of PRL. Clinical response and side-effects were similar in both drugs.

Adult↗
PubMedDate not supplied

[Allergic rhinitis in the region of Mérida].

We studied the whole of 3,047 patients who consult our unit because of a presumable allergic affection. The 20% to suffer from allergic rhinitis. The most frequent clinical presentation has been rhinitis allergic seasonal followed by perennial and to extend seasonal. We have diagnosed through by prick-test, specific IgE and ocular provocation test. The ethiology more common has been the grass pollen together olive followed pollen grass from seasonal rhinitis. The mites dust from perennial rhinitis and the grass and polisensitizations to seasonal extend.

Adolescent↗