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Biomedical subjects

F Valle

Publications and source records attributed to F Valle.

At least 37 records · Page 2Linked to original sources
PubMed1996

A pBRINT family of plasmids for integration of cloned DNA into the Escherichia coli chromosome.

Plasmid pBRINT is an efficient vector for chromosomal integration of cloned DNA into the lacZ gene of Escherichia coli [Balbás et al., Gene 136(1993) 211-213]. A family of related plasmids containing different antibiotic-resistance markers (CmR or GmR or KmR) and a larger multiple cloning site (MCS) has been constructed. This set of plasmids, whose integration efficiencies are as good as those obtained with the prototype plasmid pBRINT, constitutes a collection of tools that allow rapid and easy integration of cloned DNA, at the chromosomal level. Their functionality as integration vectors has been ascertained by integrating the Vitreoscilla sp. hemoglobin-encoding gene and the Photobacterium leiognathi lux genes. To evaluate the level of expression obtained after chromosomal integration, we constructed strains carrying one or two copies of the cat gene integrated in the chromosome, and compared their enzymatic activities with those obtained from a strain carrying cat on a multicopy plasmid.

Base Sequence↗
PubMed1996

A functional Spo0A is required for maximal aprE expression in Bacillus subtilis.

The initiation of sporulation in Bacillus subtilis is under control of the transcriptional factor Spo0A. Most Spo0A mutants fail to initiate the sporulation process and all the sporulation initiated processes such as the synthesis of subtilisin. However, the product of spo0A9V, one of the several spo0A mutants characterized, distinguishes itself in the fact that, while it appears to effectively repress abrB, it fails to activate the spoIIA operon. The aim of this study was to examine the effect of the spo0A9V mutation on aprE expression and we found that in different genetic backgrounds, the spo0A9V mutation has a negative effect on aprE::lacZ expression.

Bacillus subtilis↗
PubMed1996

Physical activity influences heart rate variability and very-low-frequency components in Holter electrocardiograms.

OBJECTIVE: A major proportion of RR interval variability in long-term recordings is due to slow (< 0.03 Hz) fluctuations, which seem to be a good predictor of survival after myocardial infarction, whose origin remains unclear. METHODS: To study the effect of physical activity we compared by spectral analysis of the RR interval in 10 healthy human subjects (aged 28[s.e. 2] years) during 1-h periods each of rest (no activity), alternating rest and mild exercise (rhythmic activity), and normal spontaneous (random) activity. RESULTS: Compared to rest, during both random and rhythmic activities, the RR variance increased significantly (from 5802[1030] to 13388[1448] ms2, P < 0.05, and to 24959[2901], P < 0.001) due to an increase in power below 0.03 Hz (from 3017[467] to 9606[966] ms2, P < 0.01, and to 21 103[2298] ms2, P < 0.001) which explained 55.4, 73.2 and 86.1% of total RR variance, respectively. CONCLUSIONS: The amount of RR variability and its slower fluctuations largely depend on physical activity, regardless of its regular or irregular occurrence. Attempts to predict cardiovascular prognosis on the basis of RR fluctuations should therefore take account of the confounding effect of physical activity since healthier subjects would probably be more active.

Adult↗
PubMed1996

Pathway engineering for the production of aromatic compounds in Escherichia coli.

Glucose is the preferred substrate for certain fermentation processes. During its internalization and concomitant formation of glucose-6-phosphate through the glucose phosphotransferase system (PTS), one molecule of phosphoenolpyruvate (PEP) is consumed. Together with erythrose 4-phosphate (E4P), PEP is condensed to form 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP), the first intermediate of the common segment of the aromatic pathway. From this metabolic route, several commercially important aromatic compounds can be obtained. We have selected Escherichia coli mutants that can transport glucose efficiently by a non-PTS uptake system. In theory, this process should increase the availability of PEP for other biosynthetic reactions. Using these mutants, in a background where the DAHP synthase (the enzyme that catalyzes the condensation of PEP and E4P into DAHP) was amplified, we were able to show that at least some of the PEP saved during glucose transport, can be redirected into the aromatic pathway. This increased carbon commitment to the aromatic pathway was enhanced still further upon amplification of the E. coli tktA gene that encodes for a transketolase involved in the biosynthesis of E4P.

3-Deoxy-7-Phosphoheptulonate Synthase↗
PubMed1996

Effect of different interventions on heart rate variability after heart transplantation: non-autonomic vs autonomic factors.

1. The human transplanted heart is initially denervated, hence any fluctuation present in the RR interval variability can be either due to reacquired innervation, or to the effect of some non autonomic activity, such as a direct effect of respiration on atrial (sinus node) stretch. 2. In order to distinguish between sympathetic, vagal and non autonomic factors we examined the effects of various physical and pharmacologic manoeuvres on the respiratory and non-respiratory components of heart rate variability. 3. We found that sinusoidal neck suction appears a useful, noninvasive tool to characterise the relative importance of the different factors, which can influence heart rate variability in the transplanted heart.

Autonomic Nervous System↗
PubMed1996

Cardiovascular reflex changes preceding episodes of vasovagal syncope in paediatric subjects.

1. The cardiovascular reflex changes preceding episodes of vasovagal syncope (VVS) in paediatric age were investigated in 12 subjects and in 20 controls, supine and upright, by spectral analysis of RR interval, respiration, systolic and diastolic blood pressure. 2. The sympatho-vagal control on the heart and blood pressure was assessed by the power of the low- (LF: index of sympathetic activity) and high-frequency oscillations (index of vagal activity to the heart). 3. In VVS group the supine blood pressure was lower than in controls and fell after tilt, while remained unchanged in controls. The blood pressure LF increased in control group during early and prolonged orthostasis, whereas in the VVS group the LF tended to decrease after early orthostasis and were not significantly greater than supine before VVS. 4. In the VVS group the sympathetic control of blood pressure appears reduced or ineffective, and progressively worsens before the VVS episode.

Adolescent↗
PubMed1996

Determinants of heart rate variability in heart transplanted subjects during physical exercise.

Respiratory sinus arrhythmia has been described in heart transplanted subjects. In order to investigate the mechanisms involved in the generation of this condition in the transplanted heart and its evolution after surgery, graded exercise was performed (0-75 W in 25 W steps) on a cycle ergometer by 41 subjects (mean age 44 years) who had undergone heart transplantation 28 months (range 3-60) earlier and by six age matched-control subjects. R-R interval, respiratory signal, O2 consumption (VO2) and CO2 production (VCO2) were measured. Respiratory sinus arrhythmia was assessed by the autoregressive power spectrum of the R-R interval and respiration. All subjects reached the anaerobic threshold (heart transplants: 60% at 50 W, 40% at 75 W Controls: 150 W). In control subjects, the respiratory sinus arrhythmia was higher than in heart transplanted subjects (5.80 +/- 0.30 vs 1.45 +/- 0.16 1n ms2) and it decreased significantly (4.66 +/- 0.30 1n ms2, P < 0.05) during exercise, despite the increase in breathing rate and depth. When, the group of heart transplanted subjects was considered as a whole, respiratory sinus arrhythmia was found to be present in all conditions. It significantly increased at 25 W (from 1.45 +/- 0.16 to 2.00 +/- 0.17 1n ms2, P < 0.01), then significantly fell below baseline during recovery (to 0.97 +/- 0.23 1n ms2, P < 0.01). Multiple regression analysis showed that a linear combination of heart rate (inverse correlation) and VO2 (direct correlation) together with months having passed since transplantation surgery, could explain the observed changes in heart rate during exercise (multiple regression: r = 0.658, P < 0.0001). In five long-term transplanted subjects, non respiratory-related low frequency (0.1 Hz) waves were present on the R-R spectrum, but respiratory sinus arrhythmia is also present in the recently transplanted heart and depends on the opposing effects of ventilation and heart rate. In a few cases, sympathetic modulation (re-innervation) could not be excluded.

Adult↗
PubMed1995

Demonstrable cardiac reinnervation after human heart transplantation by carotid baroreflex modulation of RR interval.

BACKGROUND: After heart transplantation, respiration-synchronous fluctuations (0.18 to 0.35 Hz, high frequency [HF]) in RR interval may result from atrial stretch caused by changes in venous return, but slower fluctuations (0.03 to 0.15 Hz, low frequency [LF]) not due to respiration suggest reinnervation. In normal subjects, sinusoidal neck suction selectively stimulates carotid baroreceptors and causes reflex oscillations of RR interval. METHODS AND RESULTS: To evaluate the presence of reinnervation, we measured the power of RR-LF and RR-HF in 26 heart transplant recipients and 16 control subjects before and during sinusoidal neck suction at 0.1 Hz and 0.20 Hz (similar to but distinct from that of controlled respiration, 0.25 Hz) and before and during administration of atropine or beta-blocker (esmolol hydrochloride) by spectral analysis. All transplant recipients showed small respiratory HF fluctuations. Nonrespiratory LF fluctuations were present in 13 of 26 transplant recipients and increased with months since transplantation (r = .53, P < .01). HF neck suction induced a 0.20-Hz component in all 16 control subjects and none of the 26 transplant subjects. LF neck suction increased RR-LF (from 0.73 +/- 0.20 to 1.30 +/- 0.26 ln ms2, P < .001), similar to but less than in control subjects (from 6.12 +/- 0.21 to 8.27 +/- 0.21 ln ms2, P < .001). Atropine reduced all fluctuations in control subjects and blocked the HF increase caused by 0.20-Hz neck suction but not the LF increase during 0.10-Hz stimulation. Neck suction-induced changes in LF fluctuations persisted after administration of atropine in transplant recipients but were attenuated by esmolol hydrochloride, suggesting sympathetic rather than vagal reinnervation. CONCLUSIONS: The presence of baroreceptor-induced RR oscillations is evidence of functional, although incomplete, autonomic reinnervation.

Adrenergic beta-Antagonists↗
PubMed1995

Cloning of the two pyruvate kinase isoenzyme structural genes from Escherichia coli: the relative roles of these enzymes in pyruvate biosynthesis.

We report the cloning of the pykA and pykF genes from Escherichia coli, which code for the two pyruvate kinase isoenzymes (ATP:pyruvate 2-O-phosphotransferases; EC 2.7.1.40) in this microorganism. These genes were insertionally inactivated with antibiotic resistance markers and utilized to interrupt one or both pyk genes in the E. coli chromosome. With these constructions, we were able to study the role of these isoenzymes in pyruvate biosynthesis.

Cloning, Molecular↗
PubMed1995

[Nitric oxide in the lower respiratory tract].

The aim of this work is to review of the role of nitric oxide (NO) in the lower respiratory tract. This review mainly focuses on the generation of nitric oxide by alveolar macrophages. In the first part of the paper, we summarize the literature on nitric oxide synthesis by different cell types and the effects of this mediator on target cells. Methods for measuring nitric oxide are also analyzed. The core of the paper is a review of the role of nitric oxide in diffuse interstitial lung diseases (both human and experimental models). We include data about the concentration of this mediator in bronchoalveolar lavage fluid and then summarize the knowledge about the regulation of nitric oxide synthesis by animal or human alveolar macrophages. Finally, we review the biological effects of nitric oxide in the lower respiratory tract.

Animals↗
PubMed1994

Production in Escherichia coli of a rat chimeric proinsulin polypeptide carrying human A and B chains and its preparative chromatography.

A pseudohuman proinsulin coding DNA sequence (MMRPI) carrying human A and B chains, was constructed via directed mutagenesis of a previously modified rat proinsulin cDNA (MRPI) and expressed as a tryptophan (Trp)LE-proinsulin fusion protein in Escherichia coli W3110. Expression of the hybrid gene was achieved by depletion of tryptophan from the medium. The heterologous fusion protein, accumulated as insoluble inclusion bodies within the cell, was obtained by differential centrifugation and then solubilized using formic acid. At the junction of the two peptides, a methionine residue allowed proinsulin to be released from the carrier protein by cyanogen bromide treatment. The sulfonated form of this proinsulin polypeptide was easily purified, at a preparative level, using ion exchange chromatography.

Amino Acid Sequence↗
PubMed1994

Non-respiratory components of heart rate variability in heart transplant recipients: evidence of autonomic reinnervation?

1. Although the high-frequency fluctuations in R-R interval (respiratory sinus arrhythmia) observed in heart transplant recipients are not a reliable marker of reinnervation because of a previously shown direct mechanical effect of breathing, the presence of a non-respiration-related low-frequency oscillation reflects rhythms generated outside the heart, and thus could be neurally mediated. 2. To evaluate the presence of reinnervation, the spontaneous variability in R-R interval was investigated, supine and after passive tilting, in 23 heart transplant recipients (age 43 years, range 23-64 years) and in 25 normotensive control subjects by autoregressive spectral analysis of low- and high-frequency spontaneous fluctuations in R-R interval and respiration. The response of R-R interval to amyl nitrite inhalation was also evaluated in five heart transplant recipients and eight control subjects. 3. Detectable low-frequency oscillations, unrelated to respiration, were present in 13/23 heart transplant recipients, particularly in those who were transplanted at least 20 months earlier (11/14). The natural logarithm of the power of low-frequency fluctuations was markedly lower than in control subjects (0.75 +/- 0.21 versus 5.62 +/- 0.20 ms2, P < 0.001). The low-frequency but not the high-frequency fluctuations correlated with time since transplantation (r = 0.44, P < 0.05). The subjects with low-frequency fluctuations showed a sudden decrease in R-R interval with amyl nitrite linearly related to the decrease in mean blood pressure (r > or = 0.94). The slopes obtained in these heart transplant recipients were comparable (although of lower values) with those obtained in control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Cardiovascular autonomic modulation in essential hypertension. Effect of tilting.

To better understand the role played by the autonomic nervous system in essential hypertension, we used autoregressive power spectrum analysis to study the noncasual oscillations in RR interval, blood pressure, and skin blood flow in 40 subjects with mild to moderate hypertension and in 25 age-matched control subjects at low frequency (index of sympathetic activity to the heart and the peripheral circulation) and high frequency, respiratory related (index of vagal tone to the heart). RR interval, respiration, noninvasive systolic blood pressure, and skin arteriolar blood flow were simultaneously and continuously recorded with subjects in the supine position and immediately after tilting. The low-frequency component was not significantly different in the two groups either at the cardiac level (control versus hypertensive subjects: 39.1 +/- 4.3 versus 39.9 +/- 3.7 normalized units [NU]) or at the vascular level (1.52 +/- 0.17 versus 1.69 +/- 0.13 ln mm Hg2). After head-up tilting, the RR interval fluctuations were less in hypertensive subjects (low-frequency components from 39.9 +/- 3.7 to 48.4 +/- 4.1 NU, P < .05; high-frequency components from 53.9 +/- 3.7 to 44 +/- 4 NU, P < .05) than in control subjects (low-frequency components from 39.1 +/- 4.3 to 64.4 +/- 4.9 NU, P < .001; high-frequency components from 56.0 +/- 4.5 to 31.2 +/- 4.6 NU, P < .001); the low-frequency components in systolic blood pressure increased similarly in hypertensive subjects (to 2.43 +/- 0.17 ln mm Hg2, P < .0001) and in control subjects (to 2.44 +/- 0.21 ln mm Hg2, P < .01), but the low-frequency components in skin blood flow increased only in control subjects (from 5.34 +/- 0.45 to 6.55 +/- 0.53 mm Hg2, P < .01), not in hypertensive subjects (from 5.55 +/- 0.34 to 5.60 +/- 0.35 ln mm Hg2). In hypertensive subjects with left ventricular hypertrophy, the low-frequency components in systolic blood pressure did not increase after tilting (from 1.75 +/- 0.33 to 2.05 +/- 0.41 ln mm Hg2). Baroreflex sensitivity, as assessed by spectrum analysis, was significantly lower in hypertensive than in control subjects (5.17 +/- 0.49 versus 13.18 +/- 2.44 ms/mm Hg, P < .001. Power spectrum analysis did not reveal an increased sympathetic activity or reactivity either at the cardiac or at the vascular level. The decreased baroreceptor sensitivity in hypertensive subjects could explain the reduced change in sympathovagal balance in the tilt position at the cardiac level. In hypertensive subjects without left ventricular hypertrophy, cardiopulmonary reflex deactivation induced by tilting and/or amplification of sympathetic nervous tone by arteriolar structural change could have preserved the sympathetic activation at the vascular level.

Adolescent↗
PubMed1994

[The noninvasive demonstration of functional reinnervation after heart transplantation].

Although RR interval variability appears to be an ideal method for assessing reinnervation after heart transplantation, it has been shown that respiratory sinus arrhythmia is caused by the mechanical effect of respiration on the right atrium. The neck-suction induces heart rate changes only by means of nervous reflex and its hemodynamic effect is local and hence appears as a useful method for assessing reinnervation. We tested the presence of autonomic reinnervation in 18 heart transplant recipients, compared to 12 donor-age-matched controls. We measured the power of RR interval low- (LF, around 0.1 Hz) and respiratory fluctuations (HF) before and during rhythmic neck-suction stimulation at 0.1 Hz and at a frequency (0.20 Hz) similar to, but distinct from, that of respiration (controlled at 0.25 Hz), before and during 0.04 mg/kg atropine infusion, using autoregressive spectral analysis of RR interval, respiration and neck pressure signals. The relationship between pairs of signals at each frequency was quantitatively assessed by bivariate coherence function. All transplanted subjects showed low-amplitude HF, related to respiration. Detectable LF (whose power was lower than in controls: 1.15 +/- 0.39 versus 6.08 +/- 0.27 1n-ms2, p < 0.001), non coherent with respiration, were present in 11/18 transplanted subjects, and correlated with months since transplantation (r = +0.59, p < 0.05). HF neck suction induced the presence of a 0.20 Hz fluctuation in 12/12 controls, distinct from and greater than the 0.25 Hz respiratory component (7.28 +/- 0.26 versus 6.69 +/- 0.74 1n-ms2, p < 0.01); this was not seen in any of the transplanted subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Plasmid pBRINT: a vector for chromosomal insertion of cloned DNA.

Plasmid pBRINT is a pBR322 derivative [Bolivar et al., Gene 2 (1977) 95-113; Balbás et al., Gene 50 (1986) 3-40] that allows the insertion and replacement of DNA sequences into the Escherichia coli chromosome by homologous recombination. This method uses the inability of E. coli strain ATCC47002 (JC7623) to replicate covalently closed circular (ccc) pBR322-derived plasmids, and the convenience of XGal+IPTG screening for recombinants. The vector also contains suitable selection markers (Ap and Cm), as well as a multiple cloning site (MCS) derived from the pUC vectors [Yanisch-Perron et al., Gene 33 (1985) 103-119] to facilitate cloning. A simple PCR scheme was developed to scan for DNA insertions into the bacterial chromosome. Once introduced into the chromosome, the inserted DNA sequences can be transferred to other strains by bacteriophage P1-mediated transduction.

Base Sequence↗
PubMed1993

Interferon therapy in chronic hepatitis C. Evaluation of a low dose maintenance schedule in responder patients.

Evidence has accumulated that interferon therapy can be effective in reducing transaminase levels and improving liver histology in patients with chronic hepatitis C. Unfortunately, the relapse rate after discontinuing treatment remains a problem. In this study the efficacy of a low dose of interferon was investigated for preventing relapses in patients who completely responded to a 6-month course of 3 MU 3 times a week. Eighteen out of 30 patients (60%) had normal ALT at the end of the 6th month of therapy. These patients were randomly allocated to receive either 1 MU interferon 3 times a week for 6 months or no treatment. Three patients (33.3%) without maintenance schedule and 4 (44.4%) treated with 1 MU relapsed. HCV-RNA was positive in 23 tested patients at entry and became undetectable in patients with sustained response. Relapse was associated with RNA reappearance. A post-therapy liver biopsy, performed in 8 patients, showed Knodell's score improvement. In conclusion, our study confirms the efficacy of interferon at the dose of 3 MU 3 times a week for 6 months. A low maintenance dose of interferon seems to be ineffective in preventing relapse in patients with chronic HCV infection who have responded to a prior treatment course.

Adult↗
PubMed1993

M2 mitochondrial antibodies and urinary rough mutant bacteria in patients with primary biliary cirrhosis and in patients with recurrent bacteriuria.

Primary biliary cirrhosis (PBC) patients have a higher incidence of recurrent urinary tract infection and an increased prevalence of rough forms (mutants) of E. coli in their stool samples than other chronic liver disease patients. PBC patients exhibit autoantibody reactivity against mitochondria, the most common antigen (M2) being a family of antigens with the major components having approximate molecular weights of 74, 56, 52 and 48 kD. Cross-reactivity between M2 antigen components and corresponding antigenic bands of bacteria has been demonstrated with PBC sera. Patients with recurrent urinary tract infections, all of whom had normal liver function and were taking prophylactic antibiotic treatment, had weak anti-mitochondrial antibody (AMA) reactivity (69%), with reactivity against the 74-kD antigen alone being the most common. When antibody to the 74-kD band was eluted, it was found to cross-react with bacterial membrane fractions. In the controls, 12/77 chronic liver disease patients and 2/24 normals possessed AMA. Rough forms of bacteria were found in the urine of patients with significant bacteriuria: 39% PBC, 5.3% chronic liver disease and 41% of the recurrent urinary tract infection group. M2 antibodies may be induced by urinary organisms in 'normal' women with recurrent bacteriuria and in females with PBC.

Autoantibodies↗