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Biomedical subjects

A Oliva

Publications and source records attributed to A Oliva.

At least 37 records · Page 2Linked to original sources
PubMed2001

Comparative study of protein molecular weights by size-exclusion chromatography and laser-light scattering.

High-performance size-exclusion chromatography (SEC) based on UV-Vis detection is a relative technique for molecular weight determination whereas procedure based on multi-angle laser light scattering (MALLS) is both rapid and absolute. The two methods using recombinant human growth hormone (rHGH) and beta-lactoglobulin samples were compared. A calibration curve for the chromatographic system was generated based on standard proteins and the data were fitted by least squares to a third order polynomial model. The molecular weight from the conventional SEC method for both proteins was higher than the reported values. The molecular weight of rHGH from MALLS was 23.1+/-0.57 and 21.2+/-0.80 kDa using differential refractive index (SEC-MALLS/RI) and UV (SEC-MALLS/UV-Vis) detectors as mass detectors. Both values agree, within experimental error with the molecular weight sequence of rHGH, 22.1 kDa. In contrast, the molecular weight from LS for beta-lactoglobulin was 22.5+/-0.55 kDa by SEC-MALLS/RI and 23.0+/-1.22 kDa by SEC-MALLS/UV-Vis, respectively, values always higher than those supplied by the manufacturer, 18.4 kDa. The reproducibility of the SEC-MALLS/UV-Vis method versus the SEC-MALLS/RI method was performed using the concordance correlation coefficient. The method's reproducibility was accepted by assuming a precision of 98% and a 1% loss in precision.

Chromatography, Gel↗
PubMed2001

Contribution of environmental factors to the risk of male infertility.

BACKGROUND: An increasing number of reports suggest that chemical and physical agents in the environment, introduced and spread by human activity, may affect male fertility in humans. We investigated the relationships between exposure to environmental agents and seminal characteristics, and the concentrations of reproductive hormones in the serum of men seeking infertility treatment. METHODS: We studied 225 male partners from consecutively recruited couples, who had their first infertility consultation between 1995 and 1998, in the Litoral Sur region of Argentina, one of the most productive farming regions in the world. RESULTS: A multivariate logistic regression model showed that exposure to pesticides and solvents is significantly associated with sperm threshold values well below the limit for male fertility. We also found that men exposed to pesticides had higher serum oestradiol concentrations, and that men exposed to solvents had lower LH concentrations than non-exposed men. All of these effects were greater in men with primary infertility than in men with secondary infertility. CONCLUSION: We have shown that environmental factors contribute to the severity of infertility, and that this may worsen the effects of pre-existing genetic or medical risk factors.

Agriculture↗
PubMed2001

Pyrimidine-2,4,6-Triones: a new effective and selective class of matrix metalloproteinase inhibitors.

Matrix metalloproteinases (MMPs) are a family of zinc endopeptidases that have been implicated in various disease processes. Different classes of MMP inhibitors, including hydroxamic acids, phosphinic acids and thiols, have been previously described. Most of these mimic peptides and most likely bind in a similar way to the corresponding peptide substrates. Here we describe pyrimidine-triones as a completely new class of metalloprotease inhibitors. While the pyrimidine-trione template is used as the zinc-chelating moiety, the substituents have been optimized to yield inhibitors comparable in their inhibition efficiency of matrix metalloproteinases to hydroxamic acid derivatives such as batimastat. However, they are much more specific for a small subgroup of MMPs, namely the gelatinases (MMP-2 and MMP-9).

Chelating Agents↗
PubMed2001

Lispro insulin in type 1 diabetic patients on a Mediterranean or normal diet: a randomized, cross-over comparative study with regular insulin.

Lispro (LP) and regular human (HR) insulins were compared in Type 1 diabetic (T1DM) patients on either a Mediterranean diet or normal diet. Twelve T1DM patients were recruited and randomized into two groups of 6, groups A and B. They were treated in different sequences (in 3-month intervals for 1 year). Group A: LP insulin and normal diet, LP insulin and Mediterranean diet, regular insulin and Mediterranean diet, regular insulin and normal diet. Group B: regular insulin and normal diet, regular insulin and Mediterranean diet, LP insulin and Mediterranean diet, LP insulin and normal diet. Each patient was treated with rapid acting insulin, either LP insulin or HR insulin, before each main meal and a dose of slow acting insulin at bedtime. Every 15 days the glycemic control, the incidence and frequency of hypoglycemic episodes, and any adverse events were evaluated. Every 3 months, hematology and a chemistry panel, pre- and post-prandial glycemic and insulinemic profiles were evaluated in all patients. HbA1c levels significantly decreased in LP patients on normal diet, post-prandial glycemic levels were significantly lower in LP than in HR patients from 30 min onwards, 15-min post-prandial insulin levels higher in LP- than in HR-treated patients, and hypoglycemic episodes were significantly less in LP- than in HR-treated patients. LP insulin, irrespective of the type of diet, results in more effective glycemic control, significantly reduces hypoglycemic episodes as opposed to traditional insulin therapy and seems to be more effective with a normal diet than with a Mediterranean diet.

Adolescent↗
PubMed2000

Development of two high-performance liquid chromatographic methods for the analysis and characterization of insulin and its degradation products in pharmaceutical preparations.

Two high-performance liquid chromatography methods either in reversed-phase or as size exclusion separation mode were developed and validated for the analysis of insulin and its degradation products in pharmaceutical preparations. The results show the reliability of the analytical methods for the intended used. The static and dynamic light scattering were used to characterize the insulin and its derivatives. The absolute molecular weight of human insulin monomer and dimer were 5800 and 12400 Da respectively whereas its z-average root mean square radius were 21.6+/-0.4 and 40.5+/-0.7 nm, respectively. In contrast, the hydrodynamic diameter varied between 2.69 and 5.50 nm, depending of the association behavior of insulin.

Chromatography, High Pressure Liquid↗
PubMed2000

Statistical assessment of between batch stability equivalence.

A statistical method for testing the equivalence between batches regarding their stability is proposed. This method is based on the statistical linear model making use of a set of dummy variables to code the different batches. The method gives us the point estimates of the slope and zero intercept of one batch, and the differences and the corresponding confidence intervals with the remaining batches. In a second step, zero intercepts and slopes are estimated for all the batches. Stability equivalence assessment is based on the comparison of the confidence intervals for the differences between batches with the maximum difference allowable. The main advantages of this method are the possibility to compare several batches, to disclose the equivalence stability criteria from the statistical hypothesis about the equality between slopes, and the joint estimated of the residual variance whatever the decision to pool or not the data from different batches. This method is illustrated with two data set; the first one, previously published by other authors, involved six batches; the second data set include two batches and arose in a stability study of a commercial human insulin conducted in our laboratory.

Confidence Intervals↗
PubMed2000

Angular studies of potential electron emission in the interaction of slow ions with Al surfaces

We report energy distributions of electrons emitted from Al surfaces under impact by 1 keV Ar+ and 1-5 keV Ne+ ions. The variation of the energy distributions with the angle of incidence is different for both ions and provides information on the mechanism responsible for electron emission. For Ar+ electron emission results mainly from Auger neutralization, while for Ne+ an important emission mechanism is the decay of plasmon excitations. We find a transition between surface and bulk plasmon excitations as the energy of the ion is increased.

Journal Article↗
PubMed2000

p27Kip1 accumulation is associated with retinoic-induced neuroblastoma differentiation: evidence of a decreased proteasome-dependent degradation.

Development of human neuroblastoma is due to an arrest in the differentiation program of neural crest sympathoadrenal progenitor cells. However, neuroblastomas, as well as their derived cell lines, maintain the potentiality of terminal differentiation. We investigated the molecular mechanisms by which retinoic acid, a molecule introduced in clinical trials for chemotherapy, induces differentiation in neuroblastoma cell lines. Our findings demonstrate that the retinoic acid-dependent growth arrest of LAN-5 neuroblastoma cell line is associated to a very large accumulation (>tenfold) of p27Kip1 protein, a cyclin-dependent kinase inhibitor; the protein binds and inhibits cyclin-dependent kinase 2, 4 and 6 activities, thus hampering pRb and p107 phosphorylation. p27Kip1 build-up was observable as an early phenomenon (12 - 24 h) after retinoic exposure and resulted in a time-dependent accumulation of high quantities of a free p27Kip1 form. Furthermore, retinoic treatment causes an increase of cyclin-dependent kinase 5 level and activity; however, immunoprecipitation studies proved the absence of interaction with p27kip1. No noticeable variation of other components of G1 phase cell cycle engine was observed. Pulse-chase experiments showed a remarkable elongation of p27Kip1 half-life in retinoic-treated LAN-5, while no enhancement of p27Kip1 gene expression and of the translational efficiency of its messenger RNA were demonstrated. In vivo degradation of p27Kip1 was sensitive to two highly specific proteasome inhibitors, LLnL and lactacystin, while the calpain inhibitor II ALLM and the cysteine protease inhibitor E64 did not modify the level of the protein. LLnL treatment caused a very rapid (2 h) build-up of the Cdk inhibitor content and the accumulation of higher molecular weight anti-p27Kip1 immunoreactive bands, which probably represent ubiquitinated forms of the protein. Finally, in vitro experiments demonstrated that extracts prepared from retinoic-treated LAN-5 cells degraded recombinant p27Kip1 at a rate remarkably slower than the untreated cells. Our results indicate that retinoic acid strongly increases p27Kip1 levels by down-regulating the ubiquitin-proteasome p27Kip1 degrading pathway.

Cell Cycle↗
PubMed2000

Diagnostic colors mediate scene recognition.

In this research, we aim to ground scene recognition on information other than the identity of component objects. Specifically we seek to understand the structure of color cues that allows the express recognition of scene gists. Using the L*a*b* color space we examined the conditions under which chromatic cues concur with brightness to allow a viewer to recognize scenes at a glance. Using different methods, Experiments 1 and 2 tested the hypothesis that colors do contribute when they are diagnostic (i.e., predictive) of a scene category. Experiment 3 examined the structure of colored cues at different spatial scales that are responsible for the effects of color diagnosticity reported in Experiments 1 and 2. Together, the results suggest that colored blobs at a coarse spatial scale concur with luminance cues to form the relevant spatial layout that mediates express scene recognition.

Adult↗
PubMed2000

New antineoplastic prenylhydroquinones. Synthesis and evaluation.

Several prenylhydroquinones have been prepared through Diels-Alder condensation, further functionalized or degraded chemically and then evaluated for their cytotoxic activity against some neoplastic cultured cell lines. A number of them have shown IC50 values under the microM level.

Antineoplastic Agents↗
PubMed2000

T cell receptor repertoire and function in patients with DiGeorge syndrome and velocardiofacial syndrome.

DiGeorge syndrome (DGS) and velocardiofacial syndrome (VCFS) are associated with chromosome 22q11.2 deletion. Limited information is available on the T cell receptor (TCR) Vbeta repertoire. We therefore investigated TCR Vbeta families in lymphocytes isolated from blood and thymic samples of seven patients with DGS and seven patients with VCFS, all with 22q11.2 deletion. We also studied activities related to TCR signalling including in vitro proliferation, anti-CD3-induced protein tyrosine phosphorylation, and susceptibility to apoptosis. Reduced CD3+ T cells were observed in most patients. Spontaneous improvement of T cell numbers was detected in patients, 3 years after the first study. Analysis of CD4+ and CD8+ TCR Vbeta repertoire in peripheral and thymic cells showed a normal distribution of populations even if occasional deletions were observed. Lymphoproliferative responses to mitogens were comparable to controls as well as anti-CD3-induced protein tyrosine phosphorylation. Increased anti-CD3-mediated apoptosis was observed in thymic cells. Our data support the idea that in patients surviving the correction of cardiac anomalies, the immune defect appears milder than originally thought, suggesting development of a normal repertoire of mature T cells.

Abnormalities, Multiple↗
PubMed2000

The IR1152 mutant insulin receptor selectively impairs insulin action in skeletal muscle but not in liver.

In patients harboring the IR1152 mutant insulin receptor, hepatic glucose production was normally suppressed by insulin. Hepatocytes without the insulin receptor gene and expressing IR1152 (Hep(MUT)) also showed normal insulin suppression of glucose production and full insulin response of glycogen synthase. In contrast, expression of the IR1152 mutant in skeletal muscle maximally increased glucose uptake and storage, preventing further insulin stimulation. IRS-1 phosphorylation was normally stimulated by insulin in both intact Hep(MUT) and L6 skeletal muscle cells expressing the IR1152 mutant (L6(MUT)). At variance, IRS-2 phosphorylation exhibited high basal levels with no further insulin-dependent increase in L6(MUT) but almost normal phosphorylation, both basal and insulin-stimulated, in the Hep(MUT) cells. In vitro, IR1152 mutant preparations from both the L6(MUT) and the Hep(MUT) cells exhibited increased basal and no insulin-stimulated phosphorylation of IRS-2 immobilized from either muscle or liver cells. IR1152 internalization in liver and muscle cells closely paralleled the ability of this mutant to phosphorylate IRS-2 in vivo in these cells. Block of receptor internalization (wild-type and mutant) in the liver and muscle cells also inhibited IRS-2, but not IRS-1, phosphorylation. Thus, the mechanisms controlling insulin receptor internalization differ in liver and skeletal muscle cells and may enable IR1152 to control glucose metabolism selectively in liver. In both cell types, receptor internalization seems necessary for IRS-2 but not IRS-1 phosphorylation.

Animals↗
PubMed2000

Expression of Lewis carbohydrate antigens and chromogranin A in human prostatic cancer.

The prostate specific antigen (PSA) content, the neuroendocrine differentiation and the Lewis(y) and the expression of related carbohydrate antigens in pathological prostatic tissues were determined. These included 13 cancers and 11 benign hyperplasias. PSA is expressed strongly in hyperplastic and poorly in neoplastic tissues. The neuroendocrine differentiation detected by a monoclonal antibody directed against chromogranin A (CgA) is a frequent event in carcinomas and rare in hyperplastic prostate. The Lewis(y) and related carbohydrate antigens, evaluated by the reactivity of the tissues to two monoclonal antibodies MAbB3 and MAbB1, are expressed in a considerable percentage in malignant tissues of prostate and only occasionally in benign lesions. Our results suggest that immunoblotting with antibodies against CgA, B3 and B1 on the tissues, obtained after surgery, may be useful to obtain more information on the neoplastic transformation of human prostate. Furthermore, the expression of Lewis(y) and related carbohydrate antigens on the surface of prostate cancer suggest that, following a clinical trial, an immunotoxin combination of MAbB3 or MAbB1 and Pseudomonas exotoxin, may be used in the treatment of prostate cancer.

Aged↗
PubMed2000

[Ultrasound-guided biopsy: screening of prostate cancer with a single set of 14 systematic biopsies].

Standard sextant prostate biopsy may underestimate cancer in men in whom clinical finding and transrectal ultrasound are negative and prostate-specific antigen (PSA) value suspicious for localized prostate cancer (4-10 ng/ml). We describe our experience with a 14 systematic multisite biopsy scheme to detect carcinoma of the prostate (stage T1c). Between January 1999 and February 2000, a total of 177 consecutive patients (mean age 64.1 +/- 7.7 years) underwent systematic transrectal ultrasound (TRUS) guided biopsy for normal digital rectal examination, normal TRUS and abnormal prostate specific antigen 4 ng/ml or greater (4-13 ng/ml). Fourteen core/patient were obtained not depending on prostate size. Biopsies were obtained from conventional sextant biopsies (6 core) and 3 alternate sites which included: the right and left extreme lateral peripheral zone between anterior tissue and posterior gland base (2 core); the right and left transition zone, immediately adjacent to the urethra anterior and posterior (4 core) and the right and left central gland in the mid zone typical of benign prostatic hyperplasia (BPH) (2 core). All specimens were separated for specific location identification. Adenocarcinoma was identified in 61 patients (34.46%). Traditional sextant biopsies showed 23 patients (37.7%) with positive core to detect cancer, while a sextant regimen incorporating lateral peripheral zone biopsies and transitional zone detected 19 cancer (31.1%). The combination of lateral peripheral and transitional zone alone detected cancer in 19 patients. No cancer was detected in central gland. The lateral peripheral zone was the most frequently positive site biopsy with 11 patients (57.9%) followed by the transitional zone with 8 patients (42.1%) in the group of the alternate biopsies sites. Complications of extensive biopsy included hematuria, hematospermia and limited rectal blending in 95% of patients; 1 case of fever (> 38.5 degrees C) for 3 days. Biopsies of the alternate sites are easy, feasible and reproducible. This strategy enhance prostate cancer detection of a 30% compared to conventional sextant biopsies alone. In conclusion, the 6 systematic biopsy of the peripheral zone are inadequate and a minimum of 12 with extensive core in peripheral and transitional zone should routinely be performed to detect a more significant number of men with prostate cancer at stage T1c.

Biopsy↗
PubMed1999

Dr. Angry and Mr. Smile: when categorization flexibly modifies the perception of faces in rapid visual presentations.

Are categorization and visual processing independent, with categorization operating late, on an already perceived input, or are they intertwined, with the act of categorization flexibly changing (i.e. cognitively penetrating) the early perception of the stimulus? We examined this issue in three experiments by applying different categorization tasks (gender, expressive or not, which expression and identity) to identical face stimuli. Stimuli were hybrids: they combined a man or a woman with a particular expression at a coarse spatial scale with a face of the opposite gender with a different expression at the fine spatial scale. Results suggested that the categorization task changes the spatial scales preferentially used and perceived for rapid recognition. A perceptual set effect is shown whereby the scale preference of an important categorization (e.g. identity) transfers to resolve other face categorizations (e.g. expressive or not, which expression). Together, the results suggest that categorization can be closely bound to perception.

Adolescent↗
PubMed1999

Stability study of human serum albumin pharmaceutical preparations.

The influence of temperature on the stability of human serum albumin (HSA) pharmaceutical preparations has been studied by size-exclusion high-performance liquid chromatography with multi-angle laser-light-scattering detection and by particle-size analysis. The behaviour of HSA in two pharmaceutical preparations stored at different temperatures (40, 55 and 70 degrees C) followed the same pattern--an increase in the relative percentage of dimer (MW 132 000 Da) and aggregate (MW > 200 000 Da), and then a decrease in the concentration of all species and, finally, sudden protein coagulation. These results suggest a time- and temperature-dependent process. At 70 degrees C, monomer only was detected for both preparations; the amount remaining was 83 and 72% for formulations A and B, respectively. Analysis of size-distribution curves also seems to confirm these results. Initially, three distributions were observed with length-volume mean diameters (d1,v) of 1.67, 10.6 and 57 microm. After 80 days at 55 degrees C, only two distributions were observed, with d1,v of 3.07 and 76 microm. An additional study using pure HSA at different concentrations (0.3, 2.5, 5 and 10% w/v) and storage at 75 degrees C was performed to determine the influence of the concentration of auxiliary substances and of the HSA. Only when the HSA concentration was 0.3% w/v did the remaining fraction of HSA fit a Prout-Thompkins nucleation model. Initially three distributions with mean sizes of 2, 20 and 40 microm were observed whereas at the end of the assay only one distribution, mean size 129 microm, was seen. The methodology used enabled us to separate the HSA degradation products and to determine the absolute molecular weight of albumin monomer and dimer. It is possible to conclude that the degradation mechanism for the formulations studied is complex, and that it is possible to fit the degradation data to Prout-Thompkins kinetics only when the concentration of HSA is low enough (0.3% w/v).

Chromatography, High Pressure Liquid↗
PubMed1999

[Transurethral treatment of bladder diverticuli].

Since October 1994 we performed endoscopic treatment of bladder diverticula, in combination with the resolution of cervico-urethral obstruction, in 12 patients. In a first group of five patients we used the incision of the diverticular neck, while in a second group of seven patients we associated the electrocoagulation of the diverticular mucosa to the opening of the diverticular neck. The better results have been obtained in the second group of patients in which the diverticula had markedly shrunk in two cases and had totally disappeared in five. Transurethral treatment of bladder diverticula, with incision of the diverticular neck and the fulguration of the diverticular mucosa, combined with transurethral operations for removing the obstruction of the lower urinary tract, is a safe, fast and effective method.

Aged↗