Search PubMed⌕ Search

Biomedical subjects

A Aguilera

Publications and source records attributed to A Aguilera.

At least 73 records · Page 4Linked to original sources
PubMed1998

A novel yeast gene, THO2, is involved in RNA pol II transcription and provides new evidence for transcriptional elongation-associated recombination.

We have identified two novel yeast genes, THO1 and THO2, that partially suppress the transcription defects of hpr1Delta mutants by overexpression. We show by in vivo transcriptional and recombinational analysis of tho2Delta cells that THO2 plays a role in RNA polymerase II (RNA pol II)-dependent transcription and is required for the stability of DNA repeats, as previously shown for HPR1. The tho2Delta mutation reduces the transcriptional efficiency of yeast DNA sequences down to 25% of the wild-type levels and abolishes transcription of the lacZ sequence. In addition, tho2Delta causes a strong increase in the frequency of recombination between direct repeats (>2000-fold above wild-type levels). Some DNA repeats cannot even be maintained in the cell. This hyper-recombination phenotype is dependent on transcription and is not observed in DNA repeats that are not transcribed. The higher the impairment of transcription caused by tho2Delta, the higher the frequency of recombination of a particular DNA region. The tho2Delta mutation also increases the frequency of plasmid loss. Our work not only identifies a novel yeast gene, THO2, with similar function to HPR1, but also provides new evidence for transcriptional blocks as a source of recombination. We propose that there is a set of proteins including Hpr1p and Tho2p, in the absence of which RNA pol II transcription is stalled or blocked, causing genetic instability.

Base Sequence↗
PubMed1998

Genetic stability and DNA rearrangements associated with a 2 x 1.1-Kb perfect palindrome in Escherichia coli.

We show that circular plasmids containing perfect palindromic regions of 2 x 1.1 kb can be propagated in sbcC strains of Escherichia coli, a result that is at variance with the well known observation that lambda DNA cannot tolerate palindromic regions larger than 2 x 265 bp. However, a significant fraction of these palindrome-containing plasmids can be recovered from E. coli strains either as linear molecules with hairpins at their ends or as head-to-head dimers, both in a RuvC-and RusA-independent manner. Our results suggests that large palindromes may form cruciforms in E. coli. However, palindrome-associated DNA rearrangements occur by a process that does not require any known cruciform resolvase activity. Our data support a replication-dependent model for the induction of DNA rearrangements by perfect palindromes.

Bacterial Proteins↗
PubMed1998

Stability of the peritoneal membrane in long-term peritoneal dialysis patients.

One of main challenges of peritoneal dialysis (PD) is the functional and vital long-term stability of the peritoneal membrane. Few longitudinal and controlled studies on peritoneal function have been published, and the results are somewhat contradictory. We have performed a longitudinal study with 90 patients. The overall analysis has shown that creatinine mass transfer coefficient (MTC) significantly increases and ultrafiltration (UF) capacity decreases over time. Nevertheless, urea MTC remained unaltered and MTC ratios significantly decreased after the third year. Subsequently, we examined the clinical outcomes and identified 19 patients who required peritoneal resting periods for Type I UF failure and 71 patients who did not require such a procedure. The latter patients did not show any significant functional change over time, whereas the former 19 patients showed an increase of peritoneal creatinine transport and a loss of UF capacity. These data corroborate changes in long-term peritoneal function in approximately 20% of PD patients. These changes consist of an increase in effective exchange area, peritoneal permeability, or both, accompanied by signs suggestive of mesothelial regenerative capacity loss. Infectious peritoneal injuries, especially appearing during late PD periods, are deleterious to the peritoneum. The remainder of the functional-structural changes are related to the effects of currently used dialysate. Early diagnosis, preemptive, and therapeutic measures should permit better management of long-term PD patients. The particular response to these injuries has individual characteristics that when addressed permit PD to be used long-term.

Analysis of Variance↗
PubMed1998

Recombinant human growth hormone therapy in malnourished dialysis patients: a randomized controlled study.

Recombinant human growth hormone (rhGH; Saizen, Serono, Spain) has been recently used as an anabolic agent in several catabolic states, including malnourished chronic dialysis patients. However, up-to-date, comparative studies with control groups of dialysis patients have not been reported. The aim of the present study was to assess the effects of rhGH on nutritional status in a group of malnourished adult chronic dialysis patients undergoing both continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD). The patients were randomly assigned to the control group (nine patients; 6 women, 3 men; mean age, 58.3 +/- 5.6 years; seven undergoing CAPD, two undergoing HD) or the rhGH group (eight patients; three women, five men; mean age, 63.9 +/- 3.1 years; four undergoing CAPD, four undergoing HD). Both groups were similar at baseline. All patients were given dietary prescriptions (35 kcal/kg/d and 1 g protein/kg ideal body weight/d) during 4 weeks. In the rhGH group, rhGH was administered at 0.2 IU/kg/d subcutaneously (SC) during this period. Anthropometric and analytic parameters were assessed before (0 weeks) therapy and at 2 and 4 weeks after starting therapy. The rhGH group showed an increase of 1.238 kg in body weight from 64.3 +/- 4.3 (mean +/- standard error of the mean [SEM]) to 65.6 +/- 4.9 kg (P < 0.05). Serum insulin-like growth factor type 1 (IGF-1) concentrations increased from 216.6 +/- 42.5 to 581.2 +/- 171.5 ng/mL (4 weeks; P < 0.01) and transferrin levels increased from 271.2 +/- 16.3 to 314.5 +/- 21.2 mg/dL (4 weeks; P < 0.05). A significant reduction in blood urea nitrogen (BUN) level was observed (62.1 +/- 1.8 v 46.8 +/- 3.8 mg/dL; 4 weeks; P < 0.05). Mean daily protein intake, determined by individual dietary survey, at 0 and 4 weeks, remained constant in both groups. In conclusion, weight gain and IGF-1 and transferrin level increases and BUN level decreases, despite the constant oral intake, suggest that short-term rhGH administration is associated with an anabolic reaction in malnourished dialysis patients.

Adult↗
PubMed1998

Anorexigen (TNF-alpha, cholecystokinin) and orexigen (neuropeptide Y) plasma levels in peritoneal dialysis (PD) patients: their relationship with nutritional parameters.

BACKGROUND: Malnutrition has definitely been related to mortality among dialysis patients. Persistent loss of appetite is one of the major symptoms found in these patients. It is also well recognized that several substances produce anorexia or disorders of the hunger-satiety cycle in several diseases. The aim of this study was to identify the role of anorexigen substances (TNF-alpha and cholecystokinin or CCK) and an orexigen substance (neuropeptide Y or NPY) in anorexia and malnutrition among 55 clinically stable peritoneal dialysis (PD) patients. RESULTS: High TNF-alpha plasma levels were found in 41 of 42 patients (97.6%) with a mean of 70.5+/-32.3 pg/ml. Patients with anorexia (n=11) or anorexia with nausea or vomiting (n=5) had higher TNF-alpha values than patients without these symptoms (75.9+/-34 vs 52.1 +/-24.5 pg/ml, P<0.05). Eight patients with a prior diagnosis of acid pylori disease showed higher TNF-alpha values (87.2+/-24.3) than 30 unaffected patients (63.6+/-30.5, P<0.05). TNF-alpha showed a significant negative linear correlation with retinol binding protein (RBP) (r=-0.37, n=34, P<0.05), and venous pH (r=-0.4, n=42, P<0.01); also, TNF-alpha values higher than 65 pg/ml were inversely associated with transferrin, cholesterol, blood urea nitrogen (BUN) and CCK. Patients with prealbumin levels lower than 30 mg/dl, a BMI lower than 30 kg/m2, nPCR lower than 1.1 g/kg/day and urea KT/V lower than 2.2 showed higher serum TNF-alpha levels. Patients who had been on CAPD treatment for longer periods showed higher TNF-alpha values. High plasma CCK levels were found in 38 of 45 patients (84%), mean 45.9+/-32.3 pg/ml. Patients with anorexia had no difference in CCK values compared with those without. A direct association was found between CCK levels and some nutritional markers (albumin, fibronectin, triglycerides, folic acid and nPCR in non diabetic patients). Although CCK has a recognized anorectic effect, this direct association might be because of an abnormal stimulation of CCK glucose feedback (trypsin) due to continuous peritoneal glucose absorption. This suggests that CCK could be an immediate food intake marker in PD patients. The NPY plasma levels were normal in 33 patients, high in 6 and low in 11. Patients with anorexia showed lower NPY levels than those without. NPY values greater than 50 pg/ml were directly associated with higher transferrin, prealbumin, RBP, nPCR and urea KT/V values. Importantly, a negative linear correlation between NPY and TNF-alpha was found (r=-0.42, n= 41, P<0.01). There was no significant relationship between residual renal clearance and the serum levels of the three peptides. CONCLUSION: In conclusion, our data suggest that high TNF-alpha and low NPY serum levels are associated with anorexia. High TNF-alpha, low CCK and low NPY serum levels are also related to a poor nutritional status. Further research on these circulating substances is required.

Adult↗
PubMed1998

Consequences of peritonitis episodes appearing late during peritoneal dialysis (PD) in patients able to continue PD.

The lack of specific information on the peritoneal-function consequences of late peritonitis episodes, and the concern about long-term consequences of peritoneal dialysis (PD), have prompted us to study the peritoneal function of long-term PD patients after a late peritonitis episode. The question is: Is the peritoneum more vulnerable to infections, in terms of functional effects, after a long time on PD? Forty-nine patients observed from baseline to the first year of PD with no peritonitis constituted the "early" control group; 31 other patients had one episode of peritonitis in the same period. Twenty-seven patients with no peritonitis from the fourth to fifth years comprised the "late" control group; 15 other patients had one episode during the same period. The results presented here suggest that peritoneal vulnerability to infectious episodes depends on the PD stage in which they appeared. Certainly, episodes with similar aggressive capacity in terms of inflammation duration (3-4 days) happening during the fifth year led to a loss of ultrafiltration (UF) capacity that does not appear in patients who suffer an episode during the first PD year. A remarkable feature is that this UF-capacity decrease is not accompanied by the usual creatinine mass transfer coefficient increase. This fact suggests that the dependence between peritoneal-glucose-gradient maintenance and water transport has been partially modified over time on PD. In conclusion, late mild peritonitis has distinct peritoneal-function consequences relative to early peritonitis. Patients who continue PD after one late episode showed an accentuation of the usual change which happens on long-term PD, the loss of peritoneal ultrafiltration capacity.

Creatinine↗
PubMed1997

The yeast HPR1 gene has a functional role in transcriptional elongation that uncovers a novel source of genome instability.

The yeast HPR1 gene plays an important role in genome stability, as indicated by the observation that hpr1 mutants have high frequencies of DNA repeat recombination and chromosome loss. Here we report that HPR1 is required for transcriptional elongation. Transcription driven from constitutive and regulated yeast promoters cannot elongate through the bacterial lacZ coding region in hpr1Delta cells, but progresses efficiently through other sequences such as yeast PHO5. We show that HPR1 is not required for transcription activation and that the previously reported effects of hpr1Delta on the activation of different promoters is a consequence of the incapacity of hpr1Delta cells to elongate transcription through lacZ, used as reporter. Transcriptional defects are also observed in yeast DNA sequences of hpr1Delta cells in the presence of the transcription elongation inhibitor 6-azauracil. In all cases, the blockage of transcription elongation in hpr1Delta is associated with both the high frequency of deletions and the increase in plasmid instability that we report here. Therefore, in addition to the identification of a new element involved in transcriptional elongation, our work provides evidence for a new source of genomic instability.

Chromosome Deletion↗
PubMed1997

Recombination between DNA repeats in yeast hpr1delta cells is linked to transcription elongation.

The induction of recombination by transcription activation has been documented in prokaryotes and eukaryotes. Unwinding of the DNA duplex, disruption of chromatin structure or changes in local supercoiling associated with transcription can be indirectly responsible for the stimulation of recombination. Here we provide genetic and molecular evidence for a specific mechanism of stimulation of recombination by transcription. We show that the induction of deletions between repeats in hpr1delta cells of Saccharomyces cerevisiae is linked to transcription elongation. Molecular analysis of different direct repeat constructs reveals that deletions induced by hpr1delta are specific for repeat constructs in which transcription initiating at an external promoter traverses particular regions of the DNA flanked by the repeats. Transcription becomes HPR1 dependent when elongating through such regions. Both the induction of deletions and the HPR1 dependence of transcription were abolished when a strong terminator was used to prevent transcription from proceeding through the DNA region flanked by the repeats. In contrast to previously reported cases of transcription-induced recombination, there was no correlation between high levels of transcripts and high levels of recombination. Our study provides evidence that direct repeat recombination can be induced by transcriptional elongation.

Fungal Proteins↗
PubMed1997

Nandrolone decanoate reduces serum lipoprotein(a) concentrations in hemodialysis patients.

We have studied the changes in the lipid profile of 14 chronic hemodialysis patients receiving a 6-month cycle of nandrolone decanoate as treatment for anemia. Nandrolone decanoate was administered in a weekly intramuscular dose of 200 mg and resulted in an increase in the hemoglobin concentration (baseline, 7.9 +/- 0.9 g/dL; month 6, 10.8 +/- 1.7 g/dL; P < 0.001, ANOVA) and also produced relevant modifications in the lipid concentrations. The most significant finding was a decrease in the concentration of lipoprotein(a) [Lp(a)]: baseline, 19.8 mg/dL (median), month 2, 10.6 mg/dL; month 4, 8.7 mg/dL; and month 6, 7.1 mg/dL (P < 0.001, Friedman). Other lipid changes induced by nandrolone decanoate were an increase in the concentrations of apolipoprotein B (P < 0.02, ANOVA) and triglyceride (P = NS, ANOVA) and a decrease of high-density lipoprotein (HDL) cholesterol (P < 0.001, ANOVA) and apolipoprotein A-I (P = NS, ANOVA). The decrease in HDL cholesterol was at the expense of the HDL2 cholesterol subfraction, whereas HDL3 remained unchanged. These lipid modifications were reversible; 4 months after nandrolone decanoate withdrawal, the lipid concentrations were similar to the basal values. The changes in Lp(a) levels did not correlate with those of hemoglobin or the other lipid parameters, suggesting that the underlying mechanisms are unrelated. Our findings could be clinically relevant if confirmed by further studies.

Aged↗
PubMed1997

The yeast HRS1 gene is involved in positive and negative regulation of transcription and shows genetic characteristics similar to SIN4 and GAL11.

We provide genetic evidence that HRS1/PGD1, a yeast gene previously identified as a suppressor of the hyper-recombination phenotype of hpr1, has positive and negative roles in transcriptional regulation. We have analyzed three differently regulated promoters, GAL1, PHO5 and HSP26, by beta-galactosidase assays of lacZ-fused promoters and by Northern analysis of the endogenous genes. Transcription of these promoters was derepressed in hrs1delta mutants under conditions in which it is normally repressed in wild type. Under induced conditions it was either strongly reduced or significantly enhanced depending on the promoter system analyzed. Constitutive transcription was not affected, as determined in ADH1 and TEF2. In addition, Hrs1p was required for mating-factor expression, telomere-linked DNA silencing and DNA supercoiling of plasmids. Furthermore, hrs1delta suppressed Ty-insertion mutations and conferred a Gal- phenotype. Many of these phenotypes also result from mutations in GAL11, SIN4 or RGR1, which encode proteins of the RNA polII mediator. We also show that gal11delta and sin4delta partially suppress the hyper-rec phenotype of hpr1 mutants, although to a lesser extent than hrs1delta. Our results provide new evidence for the connection between hpr1delta-induced deletions and transcription. We discuss the possibility that Hrs1p might be a component of the RNA polII transcription machinery.

Artificial Gene Fusion↗
PubMed1997

Satisfactory control of secondary hyperparathyroidism with low-calcium dialysate in patients not receiving vitamin D.

The use of a dialysate calcium concentration of 2.5 mEq/1 for patients not receiving vitamin D is controversial. Therefore, it has been suggested that oral calcium supplements might be sufficient to avoid a negative calcium balance which could result in a worsening of secondary hyperparathyroidism. In order to clarify these aspects, we reduced the dialysis fluid calcium level in 26 patients on chronic hemodialysis with a dialysate calcium concentration of 3.25 mEq/l, all of them receiving low doses of calcium carbonate and aluminum hydroxide. No patient received supplements with vitamin D during the previous 2 years. These patients have been dialyzed using a dialysate calcium concentration of 2.5 mEq/l for 1 year. Gradually we increased the dose of calcium carbonate and decreased the dose of aluminum hydroxide to maintain the predialysis serum calcium and phosphate concentrations between 8-10 and 4-6 mg/dl, respectively. After 1 year of hemodialysis with a low-calcium dialysate (2.5 mEq/l), the oral dose of calcium carbonate was increased from 3.5 +/- 2.6 to 9.2 +/- 5.6 g/day (p < 0.001). In 22 patients (85%) the aluminum hydroxide was stopped, and in the remaining 4 cases the dose was lowered. The reduction in the dialysate calcium concentration did not increase the incidence of hypercalcemia or hyperphosphatemia. In the whole group, we did not observe a significant variation in the levels of intact parathyroid hormone (iPTH; 324 +/- 123 vs. 311 +/- 256 pg/ ml) or alkaline phosphatase (230 +/- 115 vs. 224 +/- 127 U/l), although there was a reduction in the serum aluminum concentration (33 +/- 31 vs. 21.8 +/- 20.2 micrograms/l; p < 0.001). We analyzed the evolution of iPTH in each case. In 15 patients (58%) the iPTH concentration decreased, in 6 cases (23%) it remained stable, and in only 5 subjects (19%) there was an increase (2 of them did not take the oral calcium dosage recommended). In conclusion, a low dialysate calcium concentration (2.5 mEq/l) is safe for most patients not receiving vitamin D. But adherence of patients to high doses of oral calcium supplements is absolutely necessary.

Adult↗
PubMed1997

Frequent recurrence of secondary hyperparathyroidism after pulse oral calcitriol withdrawal in PD patients.

The aim of this study was to evaluate the role of pulse oral calcitriol in the control of secondary hyperparathyroidism in peritoneal dialysis (PD) patients, addressing the effects after withdrawal. We studied 15 patients with intact parathyroid hormone (iPTH) plasma levels above 250 pg/mL. The initial calcitriol dose was 8 or 4 micrograms/week, administered in two doses, according to whether the iPTH plasma levels were above or below 400 pg/mL. This dose was modified during the follow-up according to the response. Serum iPTH levels decreased in all patients after the first month (559 +/- 243 to 212 +/- 94 pg/mL, p < 0.001). Serum calcium levels significantly increased during therapy, while serum phosphorus levels did not change. The mean duration of the treatment was 95 +/- 57 days. Nine patients reached the target iPTH levels without complications, and in 6 patients the treatment was interrupted because of hypercalcemia. One month after finishing pulse therapy, a significant decrease in serum calcium levels and an increase in iPTH levels were observed. These values were similar to baseline data and were significantly higher than those found during the pulse calcitriol period. Pulse oral calcitriol administration seems to be a short-term, efficient therapy for secondary hyper-parathyroidism in PD patients. However, after the end of pulse therapy, iPTH serum levels return to baseline values, suggesting long-term therapeutic failure.

Administration, Oral↗
PubMed1996

Differential intrachromosomal hyper-recombination phenotype of spt4 and spt6 mutants of S. cerevisiae.

In order to test whether mutations affecting transcription also affect DNA recombination, we have determined the influence of a number of snf/swi and spt/sin transcriptional regulatory mutations on the recombination of a DNA inverted repeat. Among the nine different mutations analyzed, we found that spt4 and spt6 confer a significant hyper-recombination phenotype. Both mutations produced increases in the frequencies of reciprocal exchange/gene conversion and deletion events ranging from 1- to 15-fold above the wild-type levels, as determined in six direct repeat systems and one inverted repeat. The frequency of mitotic recombination between homologs, determined at one chromosomal locus, was not affected. We discuss the intrachromosomal hyper-recombination phenotype of spt4 an spt6 on the basis of the possible functions of SPT4 and SPT6 on transcriptional regulation and on chromatin structure.

Chromatin↗