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R Cabezas

Publications and source records attributed to R Cabezas.

At least 19 recordsLinked to original sources
PubMed2004

Influence of exogenous insulin on C-peptide levels in subjects with type 2 diabetes.

AIM: The aim of this study was to determine whether the influence of insulin therapy on fasting and stimulated C-peptide levels in type 2 diabetic subjects is due to plasma glucose reduction or a direct effect of exogenous insulin. METHODS: Plasma glucose and serum C-peptide levels were determined before and after IV injection of 1mg glucagon on three separate days in 21 type 2 diabetic subjects. Day 1: without pharmacological treatment and fasting plasma glucose > 11.1 mmol/L; day 2: fasting plasma glucose 4.4-7.8 mmol/L, 1h after withdrawing intravenous regular insulin infusion; day 3: fasting plasma glucose 4.4-7.8 mmol/L with bed-time NPH insulin. RESULTS: Fasting and glucagon stimulated C-peptide levels were higher on day 1 than days 2 and 3. Fasting, but not stimulated C-peptide levels, were lower on day 3 than day 2. These differences were not appeared when the percentage of C-peptide increment or the C-peptide/glucose ratio were compared in the three days. CONCLUSIONS: Blood glucose reduction instead of exogenous insulin is responsible for the C-peptide decrease during insulin therapy in type 2 diabetic subjects.

Aged↗
PubMed2000

Absorbed fractions in a voxel-based phantom calculated with the MCNP-4B code.

A new approach for calculating internal dose estimates was developed through the use of a more realistic computational model of the human body. The present technique shows the capability to build a patient-specific phantom with tomography data (a voxel-based phantom) for the simulation of radiation transport and energy deposition using Monte Carlo methods such as in the MCNP-4B code. MCNP-4B absorbed fractions for photons in the mathematical phantom of Snyder et al. agreed well with reference values. Results obtained through radiation transport simulation in the voxel-based phantom, in general, agreed well with reference values. Considerable discrepancies, however, were found in some cases due to two major causes: differences in the organ masses between the phantoms and the occurrence of organ overlap in the voxel-based phantom, which is not considered in the mathematical phantom.

Algorithms↗
PubMed1998

Comparative study of transfer factor and acyclovir in the treatment of herpes zoster.

Reactivation of varicella herpes virus (VHV), latent in individuals who have previously suffered varicella, gives rise to herpes zoster and in some cases leads to a sequela of post herpetic neuritis with severe pain which is refractory to analgesics. Many different antiviral agents have been tried without achieving satisfactory results. Of all the antiviral agents employed, acyclovir has been the most successful in reducing post herpetic pain. However acyclovir has not been as reliable as interferon alpha (IFN-alpha). We have previously looked into the use of transfer factor (TF) as a modulator of the immune system, specifically with respect to its effectiveness in the treatment of herpes zoster. In this work findings from a comparative clinical evaluation are presented. A double blind clinical trial of TF vs acyclovir was carried out in which 28 patients, presenting acute stage herpes zoster, were randomly assigned to either treatment group. Treatment was administered for seven days and the patients were subsequently submitted to daily clinical observation for an additional 14 days. An analogue visual scale was implemented in order to record pain and thereby served as the clinical parameter for scoring results. The group treated with TF was found to have a more favorable clinical course, P < or = 0.015. Laboratory tests to assess the immune profile of the patients were performed two days prior and 14 days after initial treatment. The results of these tests showed an increase in IFN-gamma levels, augmentation in the CD4+ cell population but not the percentage of T rosettes in the TF treated group. These parameters were however insignificantly modified in patients receiving acyclovir. Although TF treated patients showed an increase in CD4+ counts these cells remained below the levels for healthy individuals. The fact that IFN-gamma levels as well as the counts for CD4+ cells rose in the TF treated group and not in the acyclovir one is very significant and confirms the immunomodulating properties of TF.

Acyclovir↗
PubMed1998

Somatostatin and somatostatin receptor subtype gene expression in medullary thyroid carcinoma.

The possible existence of an autocrine/paracrine role for SRIF in normal and neoplastic thyroid parafollicular C cells has supported the use of SRIF analogues in the treatment of patients with medullary thyroid carcinoma (MTC). In this study, we have investigated the expression of SRIF by immunohistochemistry and RT-PCR, and the expression of SRIF receptor (SSTR) subtypes by RT-PCR, in a series of 14 MTCs. SRIF messenger RNA was detected in all cases, although immunoreactive cells were only identified in 8. SSTR messenger RNA was present in 12 out of the 14 tumors. Expression of more than 1 SSTR subtype was detected in 10 tumors. SSTR2, the subtype that preferentially binds to the SRIF analogue octreotide, was the subtype most frequently detected, whereas SSTR4 was not detected in any case. These results confirm the frequent expression of both SRIF and its receptors in MTC. The presence of different combinations of SSTR subtypes in a given patient may explain the variable clinical response to SRIF analogues and may promote the search for more selective drugs with different affinities to the various receptor subtypes.

Adolescent↗
PubMed1997

Molecular diagnosis of von Hippel-Lindau disease in a kindred with a predominance of familial phaeochromocytoma.

OBJECTIVE: To study the presence of germline mutations in the von Hippel-Lindau gene (vhl) in a kindred with a predominance of familial phaeochromocytoma in order to confirm the diagnosis of von Hippel-Lindau disease (VHLD) as well as to identify asymptomatic members. DESIGN: DNA extracted from peripheral blood was amplified by the polymerase chain reaction using oligonucleotide primers corresponding to exon 3 of the vhl gene. Specific mutations in codon 238 were screened by restriction endonuclease digestion of PCR products with Msp I. The results were confirmed by DNA sequence analysis. PATIENTS: Two generations of a family consisting of 15 individuals were studied. RESULTS: A germline missense point mutation at codon 238 of the vhl gene (CGG-->TGG; Arg-->Trp) was detected in all patients with phaeochromocytoma and in only one of the asymptomatic family members. CONCLUSION: Mutational analysis of the vhl gene in patients with familial phaeochromocytoma may permit specific diagnosis of von Hippel-Lindau disease, and is a good method for the identification of asymptomatic individuals at risk of von Hippel-Lindau disease.

Adolescent↗
PubMed1996

Sex-steroid hormone receptors in human medullary thyroid carcinoma.

Three complementary techniques were used to detect sex-steroid hormone receptors in tumor tissues from seven patients with medullary thyroid carcinoma: steroid binding analysis, enzyme immune assay, and immunohistochemistry. The presence of estrogen receptors was detected by steroid binding analysis in one of seven patients, although in very low concentrations (3.17 to 5.06 fmol/mg protein). These results were confirmed by enzyme immune assay (6.35 to 9.32 fmol/mg protein). Progesterone receptors were found in five of seven patients by steroid binding analysis (11.1 to 47.9 fmol/mg protein), and progesterone receptor results were confirmed by enzyme immune assay (8.1 to 34.1 fmol/mg protein). By immunohistochemistry, progesterone receptors were focally detected in all cases, whereas all tumors were negative for estrogen receptors. In summary, our results confirm the presence of sex-steroid hormone receptors, particularly progesterone receptors in medullary thyroid carcinoma. The presence of progesterone receptors in medullary thyroid carcinoma apparently does not require the continuous presence of estrogen receptors.

Adolescent↗
PubMed1995

Proliferative activity in C-cell hyperplasia and medullary thyroid carcinoma. Evaluation by PCNA immunohistochemistry and AgNORs staining.

C cell hyperplasia (CCH) is a preneoplastic lesion that precedes the development of medullary thyroid carcinoma (MTC) in familial cases. It has been hypothesized that CCH progressively acquires the neoplastic phenotype after presenting some genetic changes that involve oncogenes and tumor suppressor genes. The proliferative activity of nodular C cell hyperplasia (NCCH) and early MTC has been assessed by PCNA (Proliferating Cell Nuclear Antigen) immunohistochemistry and nucleolar organizer regions silver staining (AgNOR) in surgical specimens of seven patients with familial MTC. The ratios of PCNA-positive nuclei in NCCH (mean 1.2, range 0.2-4) were lower than in MTC (mean 2, range 1-7%). The AgNOR scores for NCCH (mean 1.53, range 1.10-1.90) were also lower than for MTC (mean 2.10, range 1.90-2.64). The results suggest that C cells progressively acquire a higher proliferative activity in agreement with the severity of the morphologic changes in the process of hyperplasia-neoplasia that leads to widely invasive MTC.

Adolescent↗
PubMed1995

111In-octreotide and 99mTc(V)-dimercaptosuccinic acid studies in the imaging of recurrent medullary thyroid carcinoma.

Detection of recurrence from medullary thyroid carcinoma (MTC) remains a diagnostic problem, especially when increased serum tumour marker levels suggest recurrence and conventional imaging techniques are non-diagnostic. In this study, we performed 111In-octreotide and 99mTc(V)-dimercaptosuccinic acid (DMSA) scans in a series of eleven patients with MTC presenting with elevated serum tumour markers after surgery. 111In-octreotide whole body studies detected tumour in six of the eleven patients studied and detected nine tumoral localizations. 99mTc(V)-DMSA whole body studies detected tumour in five of the eleven patients studied and eight tumoral localizations. 111In-octreotide and 99mTc(V)-DMSA studies detected recurrence in all four patients with basal calcitonin levels above 1000 ng/l. We conclude that 111In-octreotide and 99mTc(V)-DMSA studies have limited sensitivity to detect recurrence in patients with MTC, although their sensitivity may improve with high serum calcitonin levels. These radionuclide imaging techniques should be employed when conventional imaging techniques are negative or inconclusive or, in the case of 111In-octreotide studies, should be employed when we went to investigate the presence of somatostatin receptors that provide the basis for treatment with somatostatin analogues.

Adult↗
PubMed1993

[Bartter's syndrome: variability and clinical course].

The clinical, hydroelectrolytical and hormonal features, as well as the treatment of 3 patients with Bartter's syndrome are analyzed. The patients consulted due to severe hypokalaemia with little clinical expression (paresthesiae, carpopedal spasms, polyuria, polydipsia and/or weakness). All had normal blood pressure, hypokalemia, hyperreninaemic hyperaldosteronism and a decrease in the fractional distal chloride reabsorption; hyperuricaemia was observed in two cases and hypomagnesemia in one. Treatment with oral potassium supplements and indomethacin managed to raise serum K to around the lower limit of the normal range. However, the tubular defect and hyperreninaemic hyperaldosteronism persisted. The urinary excretion of prostaglandin E2 was normal in both the patients in whom it was measured. Given the minimal clinical expression of hypokalemia despite the difficulty in correcting it, it is probable that this syndrome often remains unrecognized.

Adolescent↗
PubMed1989

[Analgesic effect of a somatostatin analog, SMS 201-995, on headache associated with tumor of the hypophysis].

A female is reported with a pituitary tumor secreting growth hormone which remained active and induced invalidating headache in spite of previous treatment with surgery and radiotherapy. Treatment with the sustained action somatostatin analogue, SMS 201-995, was started and headache was improved in a matter of minutes, even if normalization of hormone hypersecretion was not demonstrated. The pathophysiological mechanisms possibly implicated in the improvement are discussed, and this therapeutic option in patients with headache unresponsive to common analgesics is emphasized.

Adenoma↗
PubMed1989

Theophylline-isoniazid interaction.

Drugs influencing hepatic microsomal enzyme systems, such as isoniazid, may affect the elimination pattern of theophylline. The case reported here refers to an adult female patient with a history of chronic asthma and intestinal tuberculosis who, during isoniazid therapy, presented with theophylline plasma concentrations above the therapeutic range and developed toxic symptoms. The initial episode of theophylline toxicity occurred after one month of coadministering isoniazed 300 mg/d and theophylline 350 mg bid. The theophylline plasma concentration during this episode was 24.1 micrograms/mL and was associated with the typical symptoms of theophylline toxicity. Rechallenge with isoniazide 300 mg/d and theophylline 400 mg bid showed a progressive increase in trough morning theophylline plasma levels, reaching a toxic concentration of 25.1 micrograms/mL on day 55. After withdrawal of isoniazid, theophylline concentrations gradually declined, reaching 12.9 micrograms/mL in 35 days. Theophylline toxicity in this patient might have been induced by chronic administration of isoniazid.

Adult↗
PubMed1977

Blood and saliva salicylate measurement in the monitoring of salicylate therapy.

Total and free plasma salicylate as well as saliva salicylate was measured in 13 patients with rheumatoid arthritis treated with different doses of acetylsalicylic acid alone. Although the clinical response was judged moderately effective to effective in all cases, total and free plasma salicylate varied markedly. Saliva salicylate correlated well with both total plasma salicylate and fre plasma salicylate. Determination of saliva salicylate may be a simple and useful technique for the monitoring of salicylate therapy.

Adult↗