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Biomedical subjects

P Ballesteros

Publications and source records attributed to P Ballesteros.

At least 19 recordsLinked to original sources
PubMed2003

Phase II study of weekly irinotecan (CPT-11) as second-line treatment of patients with advanced colorectal cancer.

This phase II trial studied the antitumor effect and toxicity of weekly irinotecan (CPT-11, 125 mg/m(2) 60 min iv infusion, weekly for 4 wk plus 2 wk rest) as second-line chemotherapy in patients with advanced colorectal cancer (CRC) resistant or refractory to prior 5-fluorouracil (5-FU) therapy. Sixty-nine patients with adenocarcinoma (57% in the colon and 43% in the rectum) were enrolled. The median number of treatment cycles received per patient was 4 (range, 1-6). Overall response rate was 18% (95% CI, 9-26), with 4 complete responses (6%) and 8 partial responses (12%), and a median duration of response of 8.1 mo (95% CI, 4.2-12.1). Stable disease was observed in 19 patients (28%). The median time to disease progression was 5.2 mo (95% CI, 4.3-6.1), and the median overall survival was 13.3 mo (95% CI, 9.8-16.8 months). The toxicity profile was favorable: grade 3/4 delayed diarrhea was observed in 10 patients (14.5%) in one cycle each, and grade 3/4 neutropenia in 6 patients (8.7%) and 6 cycles (3.3%). No febrile neutropenia or infection was documented. Grade 3/4 nausea and vomiting were reported in 1 (1.4%) and 7 patients (10.1%), respectively. In conclusion, this phase II trial showed a response rate and a toxicity profile of weekly CPT-11 in line with the results of prior phase II studies.

Adenocarcinoma↗
PubMed2002

Extraction and LC determination of lysine clonixinate salt in water/oil microemulsions.

A new reversed-phase high performance liquid chromatography method has been developed and validated for the quantitative determination of lysine clonixinate salt in water/oil microemulsions. The mobile phase was acetonitrile-buffer phosphate pH 3.3. Detection was UV absorbance at 252 nm. The precision and accurately of the method were excellent. The established linearity range was 5-60 microg ml(-1) (r(2)=0.999). Microemulsions samples were dispersed with chloroform and extracted lysine clonixinate salt with water. This easy method employing chloroformic extraction has been done three times. The recovery of lysine clonixinate salt from spiked placebo and microemulsion were >90% over the linear range.

Analgesics↗
PubMed2002

Combined vascular and extracellular pH imaging of solid tumors.

The unique physiological environment of solid tumors, frequently characterized by areas of poor flow, hypoxia, high lactate and low extracellular pH (pHe), influences vascularization, invasion and metastasis. Thus, vascularization and the physiological and metabolic environment play permissive (and conversely preventive) roles in invasion and metastasis. By using a multi-parametric approach of combined vascular and spectroscopic imaging, we can begin to evaluate which combinations of vascular, metabolic and physiological regions in a solid tumor represent the highest 'metastatic threat'. Here, we present measurements of pHe, vascular volume and permeability from co-localized regions within a solid tumor. These studies were performed for a group of metastatic (MDA-MB-231) and non-metastatic (MCF-7) human breast cancer xenografts. In this study, we have demonstrated the feasibility of such an approach, and presented methods of analyses to detect differences in patterns of combined parameters obtained from spatially co-registered regions in a solid tumor.

Animals↗
PubMed2001

Intracellular compartmentation of pyruvate in primary cultures of cortical neurons as detected by (13)C NMR spectroscopy with multiple (13)C labels.

The intracellular compartmentation of pyruvate in primary cultures of cortical neurons was investigated by high resolution (13)C NMR using mixtures of different pyruvate precursors conveniently labeled with (13)C or unlabeled. Cells were incubated with 1-5 mM (1-(13)C, 1,2-(13)C(2) or U-(13)C(6)) glucose only or with mixtures containing 1.5 mM (1-(13)C or U-(13)C(6)) glucose, 0.25-2.5 mM (2-(13)C or 3-(13)C) pyruvate and 1 mM malate. Extracts from cells and incubation media were analyzed by (13)C NMR to determine the relative contributions of the different precursors to the intracellular pyruvate pool. When ((13)C) glucose was used as the sole substrate fractional (13)C enrichments and (13)C isotopomer populations in lactate and glutamate carbons were compatible with a unique intracellular pool of pyruvate. When mixtures of ((13)C) glucose, ((13)C) pyruvate and malate were used, however, the fractional (13)C enrichments of the C2 and C3 carbons of lactate were higher than those of the C2 and C3 carbons of alanine and depicted a different (13)C isotopomer distribution. Moreover, neurons incubated with 1 mM (1,2-(13)C(2)) glucose and 0.25-5 mM (3-(13)C) pyruvate produced exclusively (3-(13)C) lactate, revealing that extracellular pyruvate is the unique precursor of lactate under these conditions. These results reveal the presence of two different pools of intracellular pyruvate; one derived from extracellular pyruvate, used mainly for lactate and alanine production and one derived from glucose used primarily for oxidation. A red-ox switch using the cytosolic NAD(+)/NADH ratio is proposed to modulate glycolytic flux, controlling which one of the two pyruvate pools is metabolized in the tricarboxylic acid cycle when substrates more oxidized or reduced than glucose are used.

Animals↗
PubMed2001

Mapping extracellular pH in rat brain gliomas in vivo by 1H magnetic resonance spectroscopic imaging: comparison with maps of metabolites.

The value of extracellular pH (pH(e)) in tumors is an important factor in prognosisand choice of therapy. We demonstrate here that pH(e) can be mappedin vivo in a rat brain glioma by (1)H magnetic resonance spectroscopic imaging (SI) of the pH buffer (+/-)2-imidazole-1-yl-3-ethoxycarbonylpropionic acid (IEPA). (1)H SI also allowed us to map metabolites, and, to better understand the determinants of pH(e), we compared maps of pH(e), metabolites, and the distribution of the contrast agent gadolinium1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraaceticacid (Gd-DOTA). C6 cells injected in caudate nuclei of four Wistar rats gave rise to gliomas of approximately 10 mm in diameter. Three mmols of IEPA were injected in the right jugular vein from t = 0 to t = 60 min. From t = 50 min to t = 90 min, spin-echo (1)H SI was performed with an echo time of 40 ms in a 2.5-mm slice including the glioma (nominal voxel size, 2.2 microl). IEPA resonances were detected only within the glioma and were intense enough for pH(e) to be calculated from the chemical shift of the H2 resonance in almost all voxels of the glioma. (1)H spectroscopic images with an echo time of 136 ms were then acquired to map metabolites: lactate, choline-containing compounds (tCho), phosphocreatine/creatine, and N-acetylaspartate. Finally, T(1)-weighted imaging after injection of a bolus of Gd-DOTA gave a map indicative of extravasation. On average, the gradient of pH(e) (measured where sufficient IEPA was present) from the center to the periphery was not statistically significant. Mean pH(e) was calculated for each of the four gliomas, and the average was 7.084 +/- 0.017 (+/- SE; n = 4 rats), which is acid with respect to pH(e) of normal tissue. After normalization of spectra to their water peak, voxel-by-voxel comparisons of peak areas showed that N-acetylaspartate, a marker of neurons, correlated negatively with IEPA (P < 0.0001) and lactate (P < 0.05), as expected of a glioma surrounded by normal tissue. tCho (which may indicate proliferation) correlated positively with pH(e) (P < 0.0001). Lactate correlated positively with tCho (P < 0.0001), phosphocreatine/creatine (P < 0.001), and Gd-DOTA (P < 0.0001). Although lactate is exported from cells in association with protons, within the gliomas, no evidence was observed that pH(e) was significantly lower where lactate concentration was higher. These results suggest that lactate is produced mainly in viable, well-perfused, tumoral tissue from which proton equivalents are rapidly cleared.

Animals↗
PubMed2001

Is obesity a contraindication to bilateral total knee arthroplasties under one anesthetic?

Three-hundred sixteen patients who underwent 405 primary knee replacements between January 1994 and June 1999 were reviewed for the incidence of local wound and systemic complications after unilateral and simultaneous bilateral total knee arthroplasties. A body mass index of 30 or greater was used to define obesity, and patients were divided into four groups based on obesity and whether they were undergoing unilateral or bilateral total knee arthroplasties. Preoperative and postoperative knee scores were not significantly different for any patient group. Local wound complication rates did not differ between any of the study groups. Patients who were not obese who underwent unilateral total knee arthroplasty had lower systemic complication rates (3%) than the other groups; however, there was no significant difference in complication rates between patients with obesity who underwent unilateral or simultaneous bilateral total knee arthroplasties. Based on these findings, obesity does not seem to be a contraindication to bilateral total knee arthroplasties under one anesthetic.

Arthroplasty, Replacement, Knee↗
PubMed1999

Molecular crowding and viscosity as determinants of translational diffusion of metabolites in subcellular organelles.

The role of molecular crowding and viscosity on the apparent translational diffusion coefficient (ADC) of small metabolites was investigated in different subcellular organelles using the pulse-field gradient spin-echo 1H NMR technique. ADCs of metabolites with increasing radius of gyration (0.7 A < RG < 4.5 A) were measured in the cytoplasm of rat or chicken erythrocytes, in the nucleus of chicken erythrocytes, and in isolated rat liver mitochondria. Metabolite ADCs in these systems were compared with the corresponding ADCs determined in model solutions of increasing bulk viscosity but different molecular crowding. For solutions having the same viscosity, metabolite ADCs decreased with increasing concentration of cosolutes. This effect is adequately described by the modified Stokes-Einstein relationship, ADC = k/RG (1 + 2.5Phi), where k is a constant for a given temperature and Phi is an obstruction factor reporting the fractional volume of solution occupied by cosolutes, a measure of the molecular crowding in the solution. Cytoplasmic values of Phi for metabolites of different sizes did not depend exclusively on metabolite RG but on additional factors including the chemical nature of the metabolite, the presence of diffusional barriers, and metabolite-specific binding sites. In the case of water, nuclear Phi values approached those of the extracellular space while mitochondrial Phi values were significantly higher than those of the cytoplasm. Taken together, these results reveal important differences in molecular crowding within the different subcellular compartments, suggesting considerable diffusional heterogeneity for small metabolites within the different intracellular organelles.

Animals↗
PubMed1999

In vivo imaging of extracellular pH using 1H MRSI.

Tumor pH is physiologically important since it influences a number of processes relevant to tumorigenesis and therapy. Hence, knowledge of localized pH within tumors would contribute to understanding these processes. The destructiveness, poor spatial resolution, and poor signal-to-noise ratio (SNR) of current technologies (e.g., microelectrodes, 31P magnetic resonance spectroscopy) have limited such studies. An extrinsic chemical extracellular pH (pHe) probe is described that is used in combination with 1H magnetic resonance spectroscopic imaging to yield pHe maps with a spatial resolution of 1 x 1 x 4 mm3. The principle of the technique is demonstrated on a phantom. Further data are shown to demonstrate its application in vivo, and results agree with previously reported pH values. The accuracy of the reported pH measurements is <0.1 pH units, as derived from a detailed analysis of the errors associated with the technique, the description of which is included.

Animals↗
PubMed1999

N-2-(azol-1(2)-yl)ethyliminodiacetic acids: a novel series of Gd(III) chelators as T2 relaxation agents for magnetic resonance imaging.

The synthesis, physicochemical properties, and toxicological implications of a novel series of N-2-(azol-1(2)-yl)ethyliminodiacetic acids, useful as contrast agents for magnetic resonance imaging are reported. Compounds were prepared by alkylation of methyl iminodiacetate with N-2-bromoethylazoles and subsequent hydrolysis. Stability constants of the corresponding Gd(III) complexes and T1 and T2 relaxivities were determined and interpreted in terms of optimized geometries obtained by semiempirical PM3 calculations. Compounds show increased T2 relaxivity and decreased toxicity in vitro as compared to EDTA-Gd(III) complexes.

Acetates↗
PubMed1995

[Pseudomyxoma peritonei].

Pseudomyxoma peritonei is an infrequent clinical entity, characterized by peritoneal implantations organized in cyst of mucine or free peritoneal mucine. Most arise from cystadenoma or cystadenocarcinoma of the ovary and appendix, and fewer from other tumours and locations. It is more common in females, and it is usually diagnosed over the fifth decade. Three cases of pseudomyxoma peritonei are presented, two associated to appendicular carcinoma and one to carcinoma of the ovary, and the data published about this disease are reviewed.

Aged↗
PubMed1994

[Emergency hospital admission in medical services: causes, justification, social factors, and their differences in function of age].

BACKGROUND: Increasing attention has been given to the care to elderly patients in emergency departments (ED). Moreover, few data are available about final phase of the process, that is hospital admission from ED. This study was conducted to establish appropriateness, reasons and social factors related to hospital admission in medical services from ED and their age-related differences. METHODS: The Appropriateness Evaluation Protocol scale (AEP) was applied prospectively to 515 patients 15 years and older admitted to medical services through an ED. Patients who did not meet any AEP criteria were evaluated for other medical or social factors as conditions for their admission. RESULTS: The sample was composed by 303 elders (65 years and older, mean age = 77 +/- 6 years) and 212 adults (15-64 years old, mean age = 45 +/- 14). 271 elderly patients (89.4%) and 173 adults (81.6%) meet AEP criteria (p = 0.01). Hospitalary admission for diagnostic procedures is more frequent in younger than in older group (14.2% versus 6.9%, p = 0.01). No differences are detected in hospital admissions based upon strictly social factors: 7 (2.3%) in elderly group and 7 (3.3%) in younger one (p = 0.05). CONCLUSIONS: Urgent hospital admissions in medical services are justified more frequently in elderly patients. These patients are admitted for diagnostic procedures less frequently than younger group. No age-dependent difference in strictly social admissions is detected.

Age Factors↗
PubMed1994

Imidazol-1-ylalkanoic acids as extrinsic 1H NMR probes for the determination of intracellular pH, extracellular pH and cell volume.

The synthesis and biological evaluation of a novel series of extrinsic probes for intracellular pH (pHi), extracellular pH (pHo) and cell volume determination by 1H NMR is described. Imidazol-1-ylacetate, malonate, 3-glutarate and 2-succinate esters were synthesized by reaction of imidazole with alpha-bromo esters or with alpha, beta-unsaturated esters. The corresponding acids were prepared by hydrolysis. Rat erythrocytes were readily permeable to methyl imidazol-1-ylacetate, moderately permeable to diethyl 2-imidazol-1-ylsuccinate and impermeable to diethyl 3-imidazol-1-yl-glutarate esters. Imidazol-1-ylacetic acid was the only acid derivative which penetrated the erythrocyte interior when added directly to the incubation medium. Transport of the permeable compounds to the erythrocyte interior was non-saturable up to 200 mM added compound. Addition of methyl imidazol-1-ylacetate or diethyl 2-imidazol-1-ylsuccinate esters to erythrocyte suspensions, resulted in hydrolysis to imidazol-1-ylacetic acid and 2-imidazol-1-ylsuccinic acid mono-ethyl ester in the intracellular and extracellular spaces, respectively. pHi and pHo were determined from the different chemical shifts of the H-2 proton of the acid derivatives in the intracellular (H-2i) and extracellular (H-2o) compartments. In addition, the relative intracellular and extracellular volumes could be calculated from the areas of the intracellular and extracellular H-2 resonances.

Animals↗
PubMed1992

Alternating chemotherapy for small-cell lung cancer. A twelve-week schedule of six drugs.

We have treated sixty-two patients (21 with limited disease, 41 with extensive disease), on an outpatient-basis schedule of six drugs administered weekly for twelve weeks. Cyclophosphamide, 400 mg/m2, adriamycin, 20 mg/m2 and vincristine, 2 mg, full dose, were administered during weeks 1, 5 and 9; cisplatin, 50 mg/m2 and etoposide, 100 mg/m2 during weeks 2, 6 and 10; adriamycin and vincristine at the same doses during weeks 3, 7 and 11; methotrexate 30 mg/m2, during weeks 4, 8 and 12. After the first 28 patients vincristine was replaced by teniposide (VM-26) due to neurotoxicity. The overall response rate was 64.5% (complete remission 13 p., partial remission 27 p.). Toxicity grade 3-4, mainly nausea and vomiting or neutropenia, was recorded in 17 patients. Alopecia grade 1-2 was universal. One toxic death occurred from sepsis. The overall survival was 8 months (range 1-40), (95% CL: 53-77%); 8 months in limited disease (range 1-40), and 7 months in extensive disease (range 1-23). Time to treatment failure was 6 months (7 limited disease, 5 extensive disease). In conclusion, the results of this alternating schedule are poorer than those attained with standard, high-dose treatments, mainly in limited disease, but could be a less toxic option for patients with extensive disease.

Adult↗
PubMed1992

[Myopathy and zidovudine].

BACKGROUND: The aim of this study was to evaluate the frequency of appearance of myopathy in a group of patients treated with zidovudine. METHODS: A prospective study of 37 patients with positive serology for HIV treated over 180 days with zidovudine was carried out with evaluation of the clinical history, physical examination and analytical data. RESULTS: The initial mean value of creatine kinase of 76.4 U/l and 83.3 U/l following 6 months of treatment was not statistically significant. Of the 37 patients, 2 (5.4%) showed no variations in CK values, while in 4 (10.8%) there was a decrease and in 30 (81%) an increase. There was an elevation in 11 of the 15 patients (73%) who received doses equal to or lower than 90 g, 11 out of 13 (84.6%) of those who received between 90 and 145 g and 8 out of 8 (100%) of those having received doses higher than 145 g. This increase was minimum in 27 cases (92%) and important with final values of pathologic CK in 3 (8%). Two patients (5.4%) developed clinical manifestations. CONCLUSIONS: Not only the frequency and range of creatine kinase elevation but also the appearance of clinical manifestations in this study are lower than those found in the literature, probably because of the relation with the use of lower doses of zidovudine. These results do not demonstrate any relation with sex, age, risk group for the immunodeficiency status.

Acquired Immunodeficiency Syndrome↗
PubMed1992

[Spontaneous pneumothorax and Pneumocystis carinii pneumonia. Something more than a casual association?].

The association of spontaneous pneumothorax and Pneumocystis pneumonia is not frequent. The medical literature reports a ratio between 0 and 5.7%. In 18 patients admitted in our hospital, in the last two years, and diagnosed of AIDS and Pneumocystis pneumonia, we observed two cases of pneumothorax spontaneous. They represent the 11%. In one of them spontaneous pneumothorax was the first manifestation and in the other a complication of the illness. It was not possible to isolate an agent different from Pneumocystis carinii. Considering the lack of predisposition factors and the previous clinical history, we think that Pneumocystis carinii is by itself the agent responsible of this complication. In view of this possibility, spontaneous pneumothorax in a patient who belongs to an AIDS' risk group will alert the clinician to the possibility of infection with Pneumocystis carinii.

Acquired Immunodeficiency Syndrome↗