PubMed Health⌕ Search

Biomedical subjects

V López

Publications and source records attributed to V López.

At least 19 recordsLinked to original sources
PubMed2006

Attention-deficit hyperactivity disorder involves differential cortical processing in a visual spatial attention paradigm.

OBJECTIVE: Inattention is undoubtedly one of the main characteristics of Attention-deficit hyperactivity disorder (ADHD). Nevertheless, a growing corpus of evidence shows that not all attentional processes are affected in this condition. This study aimed to explore the distribution of attentional resources in children with ADHD via a spatially shifted double-oddball visual task. METHODS: We recorded event-related potentials (ERPs) for all visual stimuli. Subjects were instructed to allocate attention in a specific area of visual space while ignoring all stimuli presented outside. Ten male children (age: 9-14; mean = 11.6 +/- 2.1) who met DSM-IV criteria for the ADHD combined subtype participated in the study, along with ten age- and sex-matched healthy controls (9-14; mean = 11.2 +/- 2.3). RESULTS: ADHD subjects showed late differential cortical responses to initially suppressed irrelevant stimuli. The amplitude of early N1-P1 components were mainly modulated by stimulus location and showed no significant differences between groups, but a late P300-like positivity was clearly evoked in the ADHD group by peripheral stimuli. CONCLUSIONS: These results suggest that ADHD may not compromise the early attentional spatial filter but rather entails a different distribution of attentional resources at later stages of cortical processing. Perhaps these differences may be attributable to individual differences in attentional mechanisms. SIGNIFICANCE: ADHD may not affect initial focusing of visual attention but rather the allocation of processing resources in later stages.

Adolescent↗
PubMed2006

Polyomavirus BK nephropathy: the effect of an early diagnosis on renal function or graft loss.

Polyomavirus BK nephropathy is a new complication among renal transplant patients. We studied 664 cadaver renal transplant recipients from February 1998 to February 2005, divided into two periods: 448 (group A, February 1998 to July 2003) and 176 (group B, August 2003 to February 2005). Twenty patients (3%) developed biopsy-confirmed polyomavirus BK nephropathy; 13 (2.9%) in group A after worsening renal function and 7 (3.9%) in group B after a prospective cytologic study in urine, examining for decoy cells, and a qualitative polymerase chain reaction (PCR) assay in urine and blood. The mean time to diagnosis was higher among group A (15.0 +/- 1.6 versus 7.2 +/- 4.0 months), as was the serum creatinine (2.5 +/- 0.7 versus 2.0 +/- 0.6 mg/dL). After 12 months the serum creatinine was 2.7 +/- 1.3 versus 1.7 +/- 0.2 mg/dL, respectively. Poor prognostic factors were a persistently positive PCR in blood and viral inclusions in the control biopsy.

Adult↗
PubMed2006

[Female sexual function before and after treatment of urinary incontinence].

The prevalence of urinary incontinence is around 20% of healthy middle-aged women. Incontinence causes a negative impact on the quality of life and sexuality. From August 2002 to January 2004, 30 patients (mean age 43 years) with stress urinary incontinence (59%), overactive bladder (15%) and mixed incontinence (26%) answered the ICIQ-SF(International Consultation on Incontinence Questionnarie-Short Form) and FSFI (Female Sexual Function Index) questionnaires before and after treatment for urinary incontinence. The follow-up ranged from 12 to 53 months. Mean ICIQ score was 17 and 7 before and after treatment respectivelly (p<0,001). Overactive bladder showed the worst scores in all domains. The patients who underwent surgery increased their scores of desire (p=0,02), satisfaction (p=0,05) and total score (p=0,02). Thirteen patients which ICIQ was zero increased: desire (p<0,01), satisfaction (p=0,05) and total score (p=0,01). Urinary incontinence significantly affects the quality of life. Therefore sexual evaluation in incontinence patients is recommended.

Adult↗
PubMed2005

[Correlation between urogenital prolapse and detrusor overactivity].

PURPOSE: To evaluate the urodynamic characteristics of a series of women with stress urinary incontinence presenting various rates of vaginal prolapse. METHODS: 92 female patients were included in this study, mean age was 48 years (range 29-75). All patients underwent urogynecologic physical examination (vaginal prolapse was graded) and complete urodynamic study in order to detect the presence of detrusor overactivity. Urodynamic terminology and measurements comply with the ICS (International Continence Society) standards. Statistical significance was established below 0.05. RESULTS: 65 women (70.6%) presented anterior vaginal prolapse and 31 (33.6%) posterior vaginal prolapse. Involuntary contractions of the detrusor muscle appeared in 13 patients (20%) who had an anterior vaginal prolapse and 6 women (19.3%) who had a posterior vaginal prolapse. The existence of involuntary contractions was not associated with the diagnosis of vaginal prolapse. CONCLUSION: Our study did not show any correlation between existence of vaginal prolapse and detrusor overactivity.

Adult↗
PubMed2005

[Mycophenolate mofetil in high risk IgA glomerulonephritis].

Mesangial IgA glomerulonephritis (MIgAGn) is the most common biopsied primary glomerulonephritis worldwide, with a poor long-term prognosis for renal function in over a third of all patients. No proven therapy currently exists for MIgAGn. Recent studies have suggested some benefit with mycophenolate mofetil (MMF), especially in hypertensive patients with kidney failure and proteinuria, though other studies have failed to corroborate these findings. We report eight adult patients with biopsy proven MIgAGn followed in a single hospital. They all received angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. Compassionate use of MMF was based on the presence of clinical and analytical data suggesting a high risk of short- to medium-term progression to chronic renal failure. MMF treatment was stopped after two and three months in two patients who had advanced renal failure at the start of therapy because of disease progression and greater fluid retention. Several months later they both required dialysis and kidney transplantation. The mean duration of MMF therapy in the other six patients was 15 (range: 10-18) months. The mean serum creatinine concentration fell from 1.82 +/- 0.47 to 1.55 +/- 0.41 mg/dl (p = 0.04). Protein loss in 24-hour urine collection fell from 1.95 +/- 1.35 to 0.77 +/- 0.58 g/day (p = 0.02). These results in this low number of patients showed that treatment with MMF in high-riks patients with MIgAGn and early stage kidney failure generally stabilized the disease and reduced proteinuria. MMF was well tolerated and may be of some benefit in a subgroup of patients with MIgAGn and a poor prognosis.

Adult↗
PubMed2001

Study of the authenticity of commercial wine yeast strains by molecular techniques.

mtDNA restriction analysis has been carried out with 45 different commercial Saccharomyces wine yeast strains. The analysis with Hinf I provided unique profiles for 17 of the 45 strains and can therefore be considered as individual strains. Nevertheless, among the remaining 28 strains, only eight mtDNA restriction patterns appeared. These strains were subjected to electrophoretic karyotyping and PCR amplification of delta sequences. We concluded that the maximum discriminatory power was obtained when the results of the three techniques were combined, giving 13 different composite patterns for the 28 strains under study. The results showed evidence of mistakes during production or fraudulent practices by yeast producers, since only 30 individual strains have been identified among the 45 Saccharomyces wine yeast strains commercialised by different companies. Additionally, commercial starters of Saccharomyces uvarum and Saccharomyces bayanus have been re-identified as Saccharomyces cerevisiae.

DNA, Bacterial↗
PubMed2001

A simplified procedure to analyse mitochondrial DNA from industrial yeasts.

A rapid method based on mtDNA restriction analysis is described for yeast strain identification. The method is an adaptation of that devised by Querol et a]. [Syst. Appl. Microbiol. 15 (1992) 439] for Saccharomyces cerevisiae wine strains, and consists of the standard miniprep isolation of yeast total DNA, and the use of restriction endonucleases that recognise a large number of sites in yeast nuclear DNA, but few sites in the mitochondrial DNA. In the adapted method, the propagation of yeast cells and restriction analysis were the steps mainly affected: cell growth was reduced to 36 h by using microfuge tubes, and the restriction analysis was carried out in just 33 min using a microwave oven for DNA digestion, and minigels for restriction fragment separation. The DNA extraction procedure was performed in the same way as in the original protocol. but slightly reducing the duration of each step and scaling down the volumes of the different solutions. enzymes and reagents used. As result, a large time reduction (52.5 h) was obtained compared to the original method. The DNA obtained can be directly digested with endonucleases displaying clear restriction patterns useful for S. cerevisiae yeast strain differentiation. In addition, strains belonging to other foodborne yeast species, including spoilage yeast species, can also be identified.

DNA Restriction Enzymes↗
PubMed2001

Prevention in routine general practice: activity patterns and potential promoting factors.

BACKGROUND: Primary care physicians have a unique opportunity to deliver preventive services, but a desired level of involvement is not always attained. METHODS: We analyzed self-reported preventive activity in a stratified random sample of 635 primary care physicians to determine how often they deliver effective interventions for the prevention of cardiovascular diseases, cancer, and acquired immunodeficiency syndrome as well as to assess factors associated with a greater implementation of preventive activity in routine practice. RESULTS: More than 63% reported to ask about tobacco use or alcohol consumption or to check blood pressure to most of their new patients. On the other hand, only 33% asked about intravenous drug use, 14% about sexually transmitted diseases, and 6% about the number of sexual partners and less than 33% reported to have an appropriate criterion for any periodic preventive activity in routine daily practice. Correlates of high preventive activity included group practice, specific register of preventive activities, participation in the Program of Preventive Activities of the Spanish Society of Community and Family Medicine, and specific nursing consultation. CONCLUSIONS: Organizational factors could be used to improve preventive activity which is far from being an adequate component of routine general practice especially with regard to human immunodeficiency virus infection and periodic preventive activity for chronic diseases.

Adult↗
PubMed2001

Adenosine reverses a preestablished CCl4-induced micronodular cirrhosis through enhancing collagenolytic activity and stimulating hepatocyte cell proliferation in rats.

Cirrhosis is one of the most common causes of mortality worldwide, because hepatic dysfunction constitutes a potentially lethal condition. Having demonstrated the hepatoprotective effect of adenosine against CCl(4)-induced cirrhosis, the present study was aimed at assessing adenosine's effect on an already-established micronodular cirrhosis. Chronic administration of CCl(4) (10 weeks) induced a cirrhotic state, characterized by increased liver fibronectin and collagen types I and III content, enhanced expression of alpha-1 (I) collagen mRNA, portal hypertension, and liver dysfunction. After CCl(4) discontinuation (5 weeks), increased persitance of alpha-1 (I) collagen mRNA expression and deposition, enhanced proline incorporation into collagen and prolyl hydroxylase activity evidenced active fibrogenesis. Several weeks after CCl(4) withdrawal, deposited collagen showed an enhanced type I/III ratio, which was associated with deficient collagenolytic activity in cirrhotic livers. Liver expression of some metalloproteinases (MMPs) and of tissue inhibitors of MMPs (TIMPs) also indicated decreased collagen breakdown in cirrhotic livers. Parameters indicative of oxidative stress (mainly protein oxidation) were persistently augmented. These events were coincident with diminished regenerative capacity of the cirrhotic liver. Intraperitoneal adenosine administration to CCl(4)-induced cirrhotic rats blocked active fibrogenesis and increased the collagen degradation (most probably by decreasing liver TIMPs levels), normalizing collagen-type ratios. In addition, the nucleoside promoted an effective hepatocyte's proliferation in the cirrhotic liver and accelerated normalization of parameters indicative of liver function and oxidative stress. Thus, adenosine readily reversed an experimental cirrhosis through stimulating liver collagenolytic and proliferative capacities, as well as by accelerating functional recovery.

Adenosine↗
PubMed2001

Period focusing induced by network feedback in populations of noisy integrate-and-fire neurons.

The population dynamics of an ensemble of nonleaky integrate-and-fire stochastic neurons is studied. The model selected allows for a detailed analysis of situations where noise plays a dominant role. Simulations in a regime with weak to moderate interactions show that a mechanism of excitatory message interchange among the neurons leads to a decrease in the firing period dispersion of the individual units. The dispersion reduction observed is larger than what would be expected from the decrease in the period. This "period focusing" is explained using a mean-field model. It is a dynamical effect that arises from the progressive decrease of the effective firing threshold as a result of the messages received by each unit from the rest of the population. A back-of-the-envelope formula to calculate this nontrivial dispersion reduction and a simple geometrical description of the effect are also provided.

Animals↗
PubMed2001

Global dynamics of a network of stochastic neurons maximizes local mutual information.

We define a stochastic neuron as an element that increases its internal state with probability p until a threshold value is reached; after that its internal state is set back to the initial value. We study the local information of a stochastic neuron between the message arriving from the input neurons and the response of the neuron. We study the dependence of the local information on the firing probability alpha of the synaptic inputs in a network of such stochastic neurons. The values of alpha obtained in the simulations are the same as those obtained theoretically by maximization of local mutual information. We conclude that the global dynamics maximizes the local mutual information of single units, which means that the self-selected parameter value of the population dynamics is such that each neuron behaves as an optimal encoder.

Animals↗
PubMed2000

Fungemia with Saccharomyces cerevisiae in two newborns, only one of whom had been treated with ultra-levura.

Ultra-Levura (Upsamedica, Spain) is a yeast (Saccharomyces boulardii) widely used as a biotherapeutic agent. To date, few adverse effects have been reported, although fungemia with Saccharomyces cerevisiae can occur in weak and immunosuppressed patients. Reported here are two cases of fungemia with Saccharomyces cerevisiae. One patient had been treated with Ultra-Levura and the other contracted the infection from the first. This is the first report of infection with Saccharomyces boulardii (Saccharomyces cerevisiae) in a patient who was not being treated with the agent.

Female↗
PubMed1999

Chemical modification and site-directed mutagenesis of human liver arginase: evidence that the imidazole group of histidine-141 is not involved in substrate binding.

Native and wild-type recombinant human liver arginases (EC 3.5.3.1) were photoinactivated by Rose bengal, and protection was afforded by the competitive inhibitor l-lysine. The dissociation constant for the enzyme-protector complex was essentially equal to the corresponding K(i) value. Upon mutation of His141 by phenylalanine, the enzyme activity was reduced to 6-10% of wild-type activity, with no changes in K(m) for arginine or K(i) for l-lysine or l-ornithine. The subunit composition of active enzyme was not altered by mutation, but the mutant H141F was markedly more sensitive to trypsin inactivation and completely insensitive to inactivation by diethyl pyrocarbonate (DEPC) and photoinactivation. Species with histidine groups blocked with DEPC were also insensitive to photoinactivation. We conclude that His141, which is the target for both inactivating procedures, is not involved in substrate binding, but plays a critical, albeit not essential role in the hydrolysis of enzyme-bound substrate.

Arginase↗
PubMed1999

Evidence that histidine-163 is critical for catalytic activity, but not for substrate binding to Escherichia coli agmatinase.

Agmatinase (agmatine ureohydrolase, EC 3.5.3.11) from Escherichia coli was inactivated by diethyl pyrocarbonate (DEPC) and illumination in the presence of Rose bengal. Protection against photoinactivation was afforded by the product putrescine, and the dissociation constant of the enzyme-protector complex (12 mM) was essentially equal to the K(i) value for this compound acting as a competitive inhibitor of agmatine hydrolysis. Upon mutation of His163 by phenylalanine, the agmatinase activity was reduced to 3-5% of wild-type activity, without any change in K(m) for agmatine or K(i) for putrescine inhibition. The mutant was insensitive to DEPC and dye-sensitized inactivations. We conclude that His163 plays an important role in the catalytic function of agmatinase, but it is not directly involved in substrate binding.

Catalysis↗
PubMed1999

Manganese is essential for catalytic activity of Escherichia coli agmatinase.

Purified Escherichia coli agmatinase (EC 3.5.3.11) expressed the same activity in the absence or presence of added Mn2+ (0-5mM). However, it was strongly inhibited by Co2+, Ni2+, and Zn2+ and almost half inactivated by EDTA. Partial inactivation by EDTA yielded enzyme species containing 0.85 +/- 0.1 Mn2+/subunit, and it was accompanied by a decrease in intensity of fluorescence emission and a red shift from the emission maximum of 340 nm to 346 nm, indicating the movement of tryptophane residues to a more polar environment. The activity and fluorescence properties of fully activated agmatinase were restored by incubation of dialysed species with Mn2+. Manganese-free species, obtained by treatment with EDTA and guanidinium chloride (3 M), were active only in the presence of added Mn2+. Results obtained, which represent the first demonstration of the essentiality of Mn2+ for agmatinase activity, are discussed in connection with a possible binuclear metal center in the enzyme.

Catalysis↗
PubMed1999

Apoptosis is regulated by polyamines in the cell cycle of Chinese hamster ovary cells.

This paper deals with the relationship between the polyamine metabolism and apoptosis in the different phases of the cell cycle in a Chinese hamster ovary (CHO) cell line. Synchronously growing cells were obtained by the addition of 1.2 mM hydroxyurea and the progression through the cell cycle was monitored by determining the incorporation of 3H-thymidine in the DNA. Ornithine decarboxylase (ODC) activity showed a peak in S phase, while intracellular putrescine and spermine contents increased constantly, reaching to a maximum level at G2 phase; spermidine content doubled during G2 and increased four times during M, compared to G1. The increment in the endogenous polyamine content was associated to a diminished uptake from the medium. The apoptotic index was higher in G2 phase, coinciding with the maximum level observed in putrescine content. The results support the idea that intracellular putrescine level is closely related to apoptosis.

Animals↗