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A Rojas

Publications and source records attributed to A Rojas.

At least 19 recordsLinked to original sources
PubMed1999

Seed-specific expression patterns and regulation by ABI3 of an unusual late embryogenesis-abundant gene in sunflower.

We cloned the genomic sequences that correspond to a previously described group 1 late embryogenesis-abundant (Lea) cDNA from sunflower: Ha ds10. The Ha ds10 G1 gene had structural and gene-expression features that depart from those of other group 1 Lea genes. An intron was present at a conserved position but showed a much larger size (1024 bp). Transcription from the Ha ds10 G1 promoter was strictly seed-specific and it originated from at least two close initiation sites. The mRNAs accumulated from stages of embryogenesis that preceded seed desiccation. Ha ds10 G1 mRNA accumulation was moderately induced, by exogenous abscisic acid treatments, in immature seeds but not induced in seedlings. We observed unprecedented changes in Lea mRNA localization associated with seed desiccation: the homogeneous tissue distribution of Ha ds10 G1 mRNAs, which was characteristic of immature embryos, evolved later in embryogenesis to an asymmetric distribution within the cotyledons, with preferential mRNA accumulation in the cells of the palisade parenchyma and provascular bundles. We also showed that, in sunflower embryos, the Ha ds10 G1 promoter could be transiently activated by the Arabidopsis ABI3 transcription factor. We discuss the significance of these results regarding hypotheses of regulation and function of plant genes from the same family.

Abscisic Acid↗
PubMed1999

Nitric oxide/cGMP mediates the spasmolytic action of 3,4'-dihydroxy-5,5'-dimethoxybibenzyl from Scaphyglottis livida.

Five aromatic compounds, 3,4'-dihydroxy-5,5'-dimethoxybibenzyl (1), batatasin III (2), coelonin (3), 3,7-dihydroxy-2,4-dimethoxyphenanthrene (4), and 3,7-dihydroxy-2,4,8-trimethoxyphenanthrene (5) were isolated from the orchid Scaphyglottis livida (Lindley) Schltr. Compounds 1-5 induced a concentration-dependent inhibition of the spontaneous contractions of the rat ileum with potencies comparable or higher to that of papaverine. The relaxation evoked by compounds 1-4 was blocked by L-NAME, an inhibitor of nitric oxide synthase. It was also demonstrated that 1 increased cyclic GMP content in rat ileum rings. Compound 1-induced elevation of cGMP was inhibited by L-NAME and ODQ, inhibitors of nitric oxide synthase and soluble guanylyl cyclase, respectively. These results indicate that nitric oxide/cGMP formation constitute the signaling pathway in the spasmolytic action of compound 1.

Animals↗
PubMed1999

Acute Chagas' disease in western Venezuela: a clinical, seroparasitologic, and epidemiologic study.

A clinical, parasitologic, and serologic study carried out between 1988 and 1996 on 59 acute-phase patients in areas of western Venezuela where Chagas' disease is endemic showed 19 symptomatic patterns or groups of symptoms appearing in combination with different frequencies. The symptomatic pattern with the highest frequency was that showing simultaneously fever, myalgia, headache, and Romaña's sign, which was detected in 20% of the acute-phase patients. Asymptomatic individuals and patients with fever as the only sign of the disease made up 15% and 11.9% of the total acute cases, respectively. Statistical correlation analysis revealed that xenodiagnosis and hemoculture were the most reliable and concordant of the five parasitologic methods used; these two methods also showed the highest proportions in detecting any clinical symptomatic pattern in acute-phase patients. A similar high reliability and concordance was obtained with a direct agglutination test, an indirect immunofluorescent antibody test, and an ELISA as serologic tests, which also showed a higher proportion of positive detection of clinical patterns than parasitologic methods (P < 0.001). It is recommended that individuals coming from endemic areas showing mild and/or severe clinical manifestations should be suspected of being in contact or having been in contact with Trypanosoma cruzi, be referred for parasitologic and serologic evaluations to confirm the presumptive clinical diagnosis of acute Chagas' disease, and start specific treatment. The epidemiologic implications of the present findings are discussed and the use of similar methodology to evaluate other areas where Chagas' disease is endemic is suggested.

Acute Disease↗
PubMed1999

Myocardial parasite persistence in chronic chagasic patients.

The persistence of Trypanosoma cruzi tissue forms was detected in the myocardium of seropositive individuals clinically diagnosed as chronic chagasic patients following endomyocardial biopsies (EMBs) processed by immunohistochemical (peroxidase-anti-peroxidase [PAP] staining) and molecular (polymerase chain reaction [PCR]) techniques. An indirect immunofluorescent technique revealed antigenic deposits in the cardiac tissue in 24 (88.9%) of 27 patients. Persistent T. cruzi amastigotes were detected by PAP staining in the myocardium of 22 (84.6%) of 26 patients. This finding was confirmed with a PCR assay specific for T. cruzi in 21 (91.3%) of 23 biopsy specimens from the same patients. Statistical analysis revealed substantial agreement between PCR and PAP techniques (k = 0.68) and the PCR and any serologic test (k = 0.77). The histopathologic study of EMB specimens from these patients revealed necrosis, inflammatory infiltrates, and fibrosis, and made it possible to detect heart abnormalities not detected by electrocardiogram and/or cineventriculogram. These indications of myocarditis were supported by the detection of T. cruzi amastigotes by the PAP technique or its genome by PCR. They suggest that although the number of parasites is low in patients with chronic Chagas' disease, their potential for heart damage may be comparable with those present during the acute phase. The urgent necessity for testing new drugs with long-term effects on T. cruzi is discussed in the context of the present results.

Adult↗
PubMed1998

Circular permutants in beta-glucosidases (family 3) within a predicted double-domain topology that includes a (beta/alpha)8-barrel.

By predicting the general secondary structure for beta-glucosidases (family 3), in conjunction with existing knowledge of the circular permutants present in B. fibrisolvens and R. albus, we were able to find the canonical elements of the secondary structure. The way these elements are linked suggests that there is a double-domain topology made up of a (beta/alpha)8-barrel domain and a "mainly all-beta" domain. A number of already known conserved motifs are located within (or near) the C-terminal part of the putative parallel beta-strands of the (bet/alpha)8-barrel, which is consistent with what is known about the location of catalytical sites for enzymes that have this domain topology. Within the circular permutants, two beta/alpha units are located at the N-terminal part of the molecule, whereas the other six beta/alpha units are located at the C-terminal end. In this way, the circular permutants can be seen to have a putative discontinuous double-domain topology.

Amino Acid Sequence↗
PubMed1998

Triggering of peritoneal macrophages with IFN-alpha/beta attenuates the expression of inducible nitric oxide synthase through a decrease in NF-kappaB activation.

Triggering peritoneal macrophages with IFN-gamma and a low concentration of LPS induced the expression of the inducible form of nitric oxide synthase (iNOS). This process was significantly inhibited when IFN-alpha/beta was added during the initial 2 h after the start of IFN-gamma/LPS activation. Evaluation of the transcriptional activity using run-on assays indicated that IFN-alpha/beta inhibited the transcription of iNOS. Transfection experiments using a 1.7-kb promoter sequence corresponding to the 5' flanking region of the murine iNOS gene showed decreased promoter activity in the presence of type I IFNs. Analysis of the transcription factors that participate in iNOS expression revealed a marked decrease of NF-kappaB activation, a nuclear factor required for the transcription of this gene. The degradation of IkappaB alpha and IkappaB beta, which is required for the translocation of NF-kappaB to the nucleus, was inhibited in the presence of IFN-alpha/beta. However, the activity of other transcription factors such as IFN regulatory factor 1, which is involved in the expression of iNOS in response to IFN-gamma, was not affected by IFN-alpha/beta stimulation. These results suggest that in the presence of IFN-alpha/beta, the activity of the iNOS promoter is impaired, and this attenuated nitric oxide synthase expression could be important in pathophysiologic situations in which secretion of type I IFNs occurs.

Animals↗
PubMed1998

Pharmacokinetics of nicotinamide in cancer patients treated with accelerated radiotherapy: the experience of the Co-operative Group of Radiotherapy of the European Organization for Research and Treatment of Cancer.

BACKGROUND: The EORTC has initiated studies to combine nicotinamide with carbogen in accelerated fractionation schedules (ARCON), since for some tumour types, acute and chronic hypoxia as well as treatment protraction may prejudice the outcome of radiotherapy. The tolerable dose of nicotinamide and the optimal interval for administration need to be ascertained. AIM: Full pharmacokinetic profiles of nicotinamide concentrations in plasma were analyzed repeatedly in 15 patients to determine the inter- and intra-patient variability in peak plasma concentrations and the optimum times for administering nicotinamide as a radiosensitizer. METHODS: Nicotinamide (Nicobion) was administered in tablet form to patients with advanced head and neck and non-small cell lung carcinomas. A standard 6 g dose was given regardless of body weight after an overnight fast and at least 30 min before breakfast. In 15 patients, blood samples were taken prior to and 1, 2, 4, 6, 8, 12 and 24 h after administration of the drug. This full profile was determined on two to four occasions for the head and neck cancer patients and on two occasions for the lung cancer patients. For each profile, the maximum concentration of nicotinamide (Cmax), time to peak plasma concentration (Tmax), elimination half-lives (t1/2) and area under the curve (AUC) were determined. Compliance was recorded and nausea and vomiting were graded on a 0-3 scale. Complete profiles of the five major metabolites were also obtained. RESULTS: In the 48 complete sets of blood samples, peak plasma concentrations ranged from 787 to 2312 nmol/ml with a median value of 1166 nmol/ml. The peak plasma concentration was achieved at 1 h in only 54% of the pharmacokinetic profiles, but at this time 92% of the profiles had already exceeded the target concentration of 700 nmol/ml, the level required in the mouse for tumour radiosensitization. The median t1/2 for all 15 cases was 9.3 h, with minimum and maximum values of 4.2 and 26.8 h. The highest concentrations of nicotinamide metabolites were found to be the N-oxide, 2-pyridone and 1-methylnicotinamide. The toxicity (nausea and vomiting) was scored and found not to be correlated with any of the pharmacokinetic parameters. CONCLUSIONS: The plasma concentrations considered necessary to radiosensitize can easily be exceeded with a dose of 6 g taken as 12 x 500 mg in tablet form; 700 nmol/ml was achieved in all patients and apparently would have been achieved in most even with a considerable reduction in dose. An adequate time between administration and radiotherapy appeared to be 1 h with this drug formulation for 92% of the profiles.

Administration, Oral↗
PubMed1998

Experience with dose escalation using CHARTWEL (continuous hyperfractionated accelerated radiotherapy weekend less) in non-small-cell lung cancer.

Results from the multicentre randomized trial of CHART (continuous, hyperfractionated, accelerated radiotherapy) in non-small-cell lung cancer (NSCLC) showed a significant increase in survival (P=0.004) compared with conventional radiotherapy and a therapeutic benefit relative to late radiation-induced morbidity. However, 60% of patients died because of failure to control locoregional disease. These findings have stimulated interest in assessing the feasibility of dose escalation using a modified CHART schedule. Acute and late morbidity with a CHARTWEL (CHART WeekEnd Less) schedule of 54 Gy in 16 days was compared with that observed with 60 Gy in 18 days in patients with locally advanced NSCLC. The incidence and severity of dysphagia and of analgesia were scored using a semiquantitative clinical scale. Late radiation-induced morbidity, namely pulmonary, spinal cord and oesophageal strictures, were monitored using clinical and/or radiological criteria. Acute dysphagia and the analgesia required to control the symptoms were more severe and lasted longer in patients treated with CHARTWEL 60 Gy (P< or = 0.02). However, at 12 weeks, oesophagitis was similar to that seen with 54 Gy and did not lead to consequential damage. Early radiation pneumonitis was not increased but, after 6 months, there was a higher incidence of mild pulmonary toxicity compared with CHARTWEL 54 Gy. No cases of radiation myelitis, oesophageal strictures or of grade 2 or 3 lung morbidity have been encountered. CHARTWEL 60 Gy resulted in an enhancement of oesophagitis and grade 1 lung toxicity compared with CHARTWEL 54 Gy. These were of no clinical significance, but may be important if CHARTWEL is used with concomitant chemotherapy. These results provide a basis for further dose escalation or the introduction of concurrent chemotherapy.

Aged↗
PubMed1998

Induction of lethal mutations in experimental tumours after single and fractionated irradiations in vivo.

PURPOSE: To investigate the prolonged reduction in cellular viability (lethal mutations) of surviving cells following irradiation of tumours in vivo and to test the effects of fractionation on the expression of lethal mutations. MATERIALS AND METHODS: A mouse mammary carcinoma (CaNT) was treated with single dose or fractionated X-ray treatments in vivo and survival quantified with an in vitro excision assay soon after irradiation and at various times up to 35 days after in vitro propagation of the surviving cells. RESULTS: A dose-dependent reduction in the plating efficiency was observed in cells isolated from irradiated tumours up to 35 days and many cell generations after irradiation. Considerable heterogeneity in plating efficiency was observed in clonal cell lines isolated from individual colonies grown from irradiated tumours. Delayed expression of lethal damage was observed after fractionated irradiation, although recovery of cellular fitness was greater than after irradiation with single doses (reported previously) suggesting that this form of damage is affected by inter-fraction repair. At equi-toxic doses, delayed expression of lethal damage was similar after three compared with two fractions of radiation per day (reported previously). CONCLUSIONS: These effects indicate that conventional excision assays of tumour cell viability under-estimate the total lethal damage caused by irradiation and have implications for modelling of the response of tumours to radiotherapy. The effect of fractionation on expression of this type of damage implies the involvement of repair processes. Therefore the repair proficiency may affect the balance between the immediate and delayed reduction of viability in irradiated cells.

Animals↗
PubMed1998

Cholera toxin differentially regulates nitric oxide synthesis, tumor necrosis factor-alpha production and respiratory burst in murine macrophages.

The aim of this study was to determine if cholera toxin can modulate the expression of several macrophage effector functions. The effect of cholera toxin on the induction of NO synthesis, production of tumor necrosis factor-alpha and induction of respiratory burst was examined in the J774.A2 macrophage cell line. Pre-incubation of cell cultures with cholera toxin significantly down-regulated lipopolysaccharide-induced NO synthesis and phorbol-12-myristate-13-acetate-induced respiratory burst. Concomitant addition of cholera toxin and lipopolysaccharide to cell cultures enhanced the production of tumor necrosis factor-alpha. These effects were abrogated when cholera toxin was inactivated by heat or treated with a specific monoclonal antibody.

Animals↗
PubMed1998

In vitro effect of estradiol, progesterone, testosterone, and of combined estradiol/progestins on low density lipoprotein (LDL) oxidation in postmenopausal women.

OBJECTIVE: One of the mechanisms currently proposed to explain the cardioprotective effect of hormone replacement therapy (HRT) is the antioxidative property of estrogens. Considering that HRT involves the administration of an estrogen, usually combined with a progestin and sometimes with an androgen, we investigated the following in vitro: (1) the effect of estradiol, progesterone, and testosterone on the oxidation of low density lipoprotein; (2) the possible pro-oxidative effect of progesterone and testosterone on native low density lipoprotein; and (3) the possible modification of the antioxidant effect of estradiol on low density lipoprotein induced by progestins. DESIGN: Low density lipoprotein was isolated from blood samples obtained from 20 untreated postmenopausal women and divided in multiple aliquots, each containing 0.5 mg LDL protein. In Protocol 1 (n = 10) different doses of estradiol, progesterone, and testosterone ranging from 0 to 26 micrograms/ml were tested inducing oxidation with 15 microM copper sulfate. In Protocol 2 (n = 6) we studied the rate of oxidation of low density lipoprotein incubated with progesterone or testosterone without any oxidative induction. In Protocol 3 (n = 10) we studied the concomitant effect of 15 microM estradiol with four separate progestins (progesterone, medroxyprogesterone acetate, norethindrone, and norgestrel) in different doses (0, 5, 15, and 50 microM). After incubation for 4 h at 37 degrees C, malonaldehyde was measured as a marker of low density lipoprotein oxidation. The results were expressed in mean +/- SD. RESULTS: Protocol 1: Estradiol induced a dose-dependent decrease in malonaldehyde generation, from a baseline of 61.8 +/- 30.2 nmol/mg protein to 11.6 +/- 7.1 nmol/mg protein at the highest dose of estradiol tested (p < 0.0001). Progesterone or testosterone did not modify malonaldehyde generation. Protocol 2: Progesterone and testosterone did not show pro-oxidative action. Protocol 3: Estradiol 15 microM alone induced a 35% decrease in malonaldehyde generation, from a baseline of 75.4 +/- 25.4 to 49.3 +/- 18.8 nmol/mg protein (p < 0.0001). Norgestrel and norethindrone did not modify the antioxidant effect of estradiol (p > 0.05). Progesterone and medroxyprogesterone acetate induced a further reduction of malonaldehyde concentration to 37.2 +/- 20.8 and 38.6 +/- 18.2 nmol/mg protein, only at the highest dose tested (p < 0.02 and p < 0.01, respectively). CONCLUSIONS: Our results demonstrate that, in contrast with the potent antioxidant effect of estradiol, progesterone and testosterone did not show any pro- or antioxidant effect on low density lipoprotein in vitro. Furthermore, progestins did not counteract the antioxidant effect of estradiol in vitro.

Copper Sulfate↗
PubMed1998

[Comparison of the antioxidant effect of estriol and estradiol on low density lipoproteins in post-menopausal women].

BACKGROUND: Estradiol (E2) has a potent antioxidant effect on low density lipoproteins (LDL) in vitro and in vivo, which could be important in explaining the cardioprotective effect of hormone replacement therapy (HRT) in post menopausal women. Estriol (E3), on the other hand, is a weak estrogen with low metabolic effects on different tissues, and at present no cardioprotective effect has been attributed to this steroid. AIM: To study the antioxidant effect of E3 on LDL and to compare it with the potent antioxidant action exhibited by E2. SUBJECTS AND METHODS: After LDL was isolated by ultra centrifugation from plasma of 12 healthy untreated post menopausal women, it was divided into aliquots containing 0.5 mg of LDL protein. Estriol and E2 in doses of 0, 1, 5, 15 and 50 microM were incubated with different aliquots of LDL. CuSO4 15 microM was added to each aliquot to induce an oxidative stress. The aliquots were then incubated during 4 hours at 37 degrees C. Malonaldehyde (MDA) was measured as a marker of LDL oxidation, and expressed as nM/mg protein. RESULTS: (mean +/- SD): Estriol induced a dose-dependent decrease in MDA concentration (baseline 62.8 +/- 21.7; 1 microM: 61.5 +/- 23.0; 5 microM: 52.9 +/- 20.3; 15 microM 43.5 +/- 20.1 and 50 microM: 31.0 +/- 17.6 nM/mg protein; F = 92.4; p < 0.0001), reaching a mean decrease of 50.7% at the highest dose tested. Estradiol has a similar dose-dependent decrease in MDA concentration (F = 60.2; p < 0.0001), revealing a more potent effect than E3 (p < 0.05), with a mean decrease of 67.4% at the highest dose tested. CONCLUSIONS: Our results demonstrate that estriol shows an important antioxidant action of LDL in vitro, although its effect is less potent than estradiol. These results raise the possibility that estriol could have a cardioprotective effect in post menopausal women, possibility that has not been yet demonstrated.

Antioxidants↗
PubMed1998

[Prenatal diagnosis. II. Importance of ultrasonographic markers in prenatal diagnosis of chromosome abnormalities].

The Medical Genetic Unit of the University of Zulia (MGUUZ) has developed a Prenatal Diagnosis Program (PDP) since January-1993, in which Genetic Risk Factors are determined in couples who request prenatal genetic counseling. In this program, different prenatal diagnostic procedures are performed to detect congenital defects during intrauterine life. One of these procedures is the Fetal Sonogram (FS). FS is a non invasive technique which permits the prenatal diagnosis of many genetic dysmorphic syndromes. Through the search of abnormal specific characteristics in the fetus, chromosomopathies may be suspected. These findings are named "Echosonographic Markers of Chromosomal Abnormalities" (EMCA). During three years (January-1993 to December-1996), patients attended in the PDP included 321 pregnant women in which 312 FS were performed. Abnormal outcomes were 22 (17 with isolated congenital malformations and 5 with EMCA). Only one fetus with chromosome abnormality (46,XX21q-) could not be detected by FS. The goals of this paper are: 1) to report 5 patients with sonographic markers suggestive of chromosomal abnormalities and 2) to show the FS usefulness in prenatal diagnosis of chromosompathies. We conclude that, in the search of the EMCA the FS should be offered systematically to all pregnant women without recognizable genetic risk. They are the main group with optimal reproductive age and in consequence, with the possibility of having a relatively major number of conception outcomes with congenital defects, with or without chromosomic etiology. The majority of those defects can be detected by FS and could allow us to select the patients in which the use of an invasive prenatal diagnostic procedure could be justified.

Adolescent↗
PubMed1997

Administration of nicotinamide during a five- to seven-week course of radiotherapy: pharmacokinetics, tolerance, and compliance.

BACKGROUND AND PURPOSE: Nicotinamide was administered daily as a liquid formulation to head and neck cancer patients receiving a 5- to 7-week course of radiotherapy. The pharmacokinetics, compliance, and tolerance of this drug formulation were studied. MATERIALS AND METHODS: Blood samples were drawn and nicotinamide levels determined in 40 head and neck cancer patients. On the first treatment day serial samples were obtained followed by daily samples at the time of irradiation during the first and last full weeks of the treatment. Side-effects of nicotinamide were monitored. RESULTS: In all patients peak concentrations greater than 700 nmol/ml could be obtained 0.25-3 h (mean 0.83 +/- 0.73 h) after drug intake. During the first week of treatment plasma levels at the time of irradiation were adequate in 82% of the samples. This decreased to 59% in the last week of treatment which can be partly attributed to reduced compliance. The most important side-effect of nicotinamide was nausea with or without vomiting occurring in 65% of the patients. Severe side-effects were associated with high plasma concentrations over subsequent days. Tolerance improved after a 25% reduction of dose in six of seven patients but plasma levels at the time of irradiation fell below 700 nmol/ml in four out of six of these patients. CONCLUSIONS: Peak plasma concentrations above the 700 nmol/ml level were obtained in all patients but these concentrations could not be reproduced during the entire course of the treatment in a significant portion of the subjects. Side-effects of nicotinamide are associated with plasma concentrations and tolerance can be improved by a moderate reduction of dose.

Adult↗
PubMed1997

Carbogen and nicotinamide in the treatment of bladder cancer with radical radiotherapy.

Carbogen and nicotinamide have been evaluated in a phase II study as hypoxia-modifying agents during radical radiotherapy for bladder cancer using a standard daily 20-fraction schedule. Three groups of patients have received (a) nicotinamide alone, given orally in a dose of 80 mg kg(-1) daily with 52.5 Gy in 20 fractions over 4 weeks, (b) carbogen alone, with 50 Gy in 20 fractions over 4 weeks, and (c) carbogen and nicotinamide, with 50-52.5 Gy in 20 fractions over 4 weeks. Ten patients were treated in each group. All patients completed carbogen and radiotherapy as prescribed, but only 45% completed daily nicotinamide over the 4-week treatment period. The end points of this study were acute bowel and bladder morbidity and local control at cystoscopy 6 months after treatment. An expected level of acute bowel and bladder morbidity was seen that reverted to normal in most patients by 12 weeks with no difference between the three treatment groups. Complete response rates at 6 months were seven out of ten (100%) in the nicotinamide alone group, nine out of ten (90%) in the carbogen alone group and seven out of ten (70%) in the carbogen and nicotinamide group. It is concluded that carbogen and nicotinamide may improve the results of daily fractionated radiotherapy in bladder cancer and that further evaluation is required.

Aged↗
PubMed1997

Smooth muscle relaxing flavonoids and terpenoids from Conyza filaginoides.

Activity-guided fractionation of the smooth muscle relaxing, chloroform-methanol (1:1) extract of Conyza filaginoides (D.C.) Hieron (Asteraceae) led to the isolation of three flavonoids (quercetin 3-glucoside, rutin, and pinostrobin), one sterol (alpha-spinasterol), a sesquiterpenoid (beta-caryophyllene 4,5-alpha-oxide), and two triterpenoids (erythrodiol and 3-beta-tridecanoyloxy-28-hydroxyolean-12-ene). 3-beta-Tridecanoyloxy-28-hydroxy-olean-12-ene is a new naturally occurring terpenoid. All the isolated compounds induced a concentration-dependent inhibition of the spontaneous contractions of rat ileum. The spasmolytic activity exhibited by the extract and active principles tends to support the traditional use of C filaginoides as an antispasmodic agent.

Animals↗