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Biomedical subjects

I Tapia

Publications and source records attributed to I Tapia.

11 recordsLinked to original sources
PubMed2001

Polyphenol oxidase activity, color changes, and dehydration in table grape rachis during development and storage as affected by n-(2-chloro-4-pyridyl)-n-phenylurea.

Flame Seedless grapes were sprayed with N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU) at 0, 2.5, and 5.0 ppm to develop rachis resistant to browning and dehydration. Rachis polyphenol oxidase (PPO) activity was determined during cluster development. Cluster components were weighed at commercial (CM), and physiological maturity (PM). PPO activity, rachis color changes (L and a), and cluster weight loss were evaluated at 0 degrees C for 8, 16, 32, and 56 days. CPPU-treated rachis had a decrease of 36% in PPO activity and a week delay in peak activity. At PM, dry weight of CPPU-treated rachis increased by 3 g. Postharvest rachis PPO activity declined with CPPU application, and color changes followed the same pattern for CM and PM. After 32 days of storage, L and a in lateral branches were significantly superior in CPPU treatments. Weight losses below 2.1% were significantly lowest in CPPU-treated clusters for 16 days of storage regardless of cluster maturity.

Catechol Oxidase↗
PubMed2000

Synthesis and 5-HT3 receptor affinity of new quinolinecarboxylic acid derivatives.

A series of quinolinecarboxylic acid amides and an ester with a quinuclidine moiety were synthesized and their in vitro affinities at 5-HT3, 5-HT4, and D2 receptors evaluated by radioligand binding assays. Highest affinity at 5-HT3 receptor corresponded to derivative 5 with Ki = 9.9 nM and with selectivity over 5-HT4 and D2 receptors. Compounds displayed moderate 5-HT3 antagonist activity (ED50 = 10.5-21.5 microg/kg i.v.). The obtained data suggest that the 5-HT3 receptor sites can accommodate the acyl group of the 2-quinoline derivatives. The results indicate the existence of an optimal distance between the lone electron pair of the quinoline nitrogen atom and the azabicyclic nitrogen atom, and a no-pharmacophoric pocket in the 5-HT3 receptor which would hold the fragment at the position 4 of the quinoline ring.

Animals↗
PubMed1999

2,3-Dihydro-2-oxo-1H-benzimidazole-1-carboxamides with selective affinity for the 5-HT(4) receptor: synthesis and structure-affinity and structure-activity relationships of a new series of partial agonist and antagonist derivatives.

A series of 2,3-dihydro-2-oxo-1H-benzimidazole-1-carboxamide derivatives bearing a piperazine moiety was synthesized. Their in vitro 5-HT(4), 5-HT(3), and D(2) receptors affinities were evaluated by radioligand binding assay. For selected compounds functional studies at the 5-HT(4) receptor were made by using precontracted (by carbachol) preparations of rat esophageal tunica muscularis mucosae (TMM). The influence of the 3-substituent of the benzimidazole ring, the 4-substituent of the piperazine moiety, and the alkylene spacer was studied. Compounds with an ethyl or a cyclopropyl substituent in the 3-position of the benzimidazole ring showed moderate to high affinity (K(i) = 6.7-75.4 nM) for the 5-HT(4) receptor with selectivity over 5-HT(3) and D(2) receptors and moderate antagonist activity (pK(b) = 6.19-7.73). Compounds with an isopropyl substituent in the 3-benzimidazole position exhibited moderate and selective 5-HT(4) affinity (K(i) >/= 38.9 nM) and a partial agonist activity (5a, i.a. = 0.94) higher than that of the reference compound BIMU 8 (i.a. = 0.70). This reversal of the pharmacological activity due only to a small structural difference might confirm the existence of two binding sites on the 5-HT(4) receptor. In the alkylene spacer, a two-methylene chain is favorable to optimize the affinity and the antagonist or the partial agonist activity. In the ethyl and cyclopropyl series, 5-HT(4) antagonist activity seems to be unrelated to the size of the 4-substituent of the piperazine moiety, whereas a methyl group is optimal for high partial agonist activity in the isopropyl series; however, the presence of a butyl substituent is a favorable pattern for 5-HT(4) antagonism and even causes a reversal of the pharmacological profile in the isopropyl series (5h, pK(b) = 7.94). N-Butyl quaternization of 5a led to an improvement in affinity for the 5-HT(4) receptor and mantained the high partial agonist activity (5r, K(i) = 66.3 nM, i.a. = 0.93).

Amides↗
PubMed1993

[Duodenogastric reflux: values in normal children and in children with gastroesophageal reflux].

Duodenogastric reflux (DGR) is a natural event, occurring occasionally and whose pathological significance is not well known. The accuracy of 24-hour gastric pH-metry for the DGR diagnosis has been tested in adults but not in children. For this purpose we measured the area under curve (AUC) at pH 4, 6 and 7 and the percentage of total time above pH 4 (%pH4), 6 (%pH6) and 7 (%pH7), excluding the 2-hours post-prandial period in 88 children suspected of having gastroesophageal reflux (GER). Forty were considered normal whereas 40 had acid GER and 8 with GER. In the control group %pH4 was 9.68 +/- 14.1, %pH6 3.4 +/- 8.7 and %pH7 1.0 +/- 2.4. The values for AUC were 101 +/- 112.8, 16.5 +/- 22.3 and 3.3 +/- 6.1 pH unit/min, respectively. Comparable results were found in the acid GER group. On the other hand alkaline refluxes had higher figures for all parameters: %pH4 22.1 +/- 13.9, %pH6 12 +/- 13 y %pH7 7 +/- 12, AUC at pH 4,406.5 +/- 410, 136.1 +/- 194 at pH6 and 48.2 +/- 85.1 at pH7 (p < 0.05). Because of the large dispersion of values in the control group we selected the 95 percentile, as the upper limit of normal values instead of the mean +/- SD. Therefore the upper limit were 27 for %pH4, 9 for %pH6 and 3.8 for %pH7. The AUC, 316, 64 and 16 pH/min, respectively. These results prove that DGR in children is a very common event and confirm that DGR definitely contributes to alkaline GER.

Adolescent↗
PubMed1993

[Alkaline gastroesophageal reflux. Diagnosis by double-channel pH measurement].

Alkaline gastroesophageal reflux (AGER) has been documented in adult subjects, but few in pediatrics. 24-hours double pH-monitoring was performed in 40 nonrefluxers (control group) and 69 gastroesophageal reflux (RGE) children to quantify AGER. Esophageal phmetric variables were measured at 4 and 7 levels; gastric variables were measured at 4. Forty cases were classified into acid GER, 15 into acid alkaline GER (mixed), 8 into AGER, and 6, with clinical, manometric or endoscopic evidence of GER into "silent" GER. The acid and mixed GER groups had longer periods of acid exposure in esophagus than control, AGER and "silent" GER groups. All groups had long periods of pH > 7 in esophagus. In conclusion, the double gastroesophageal pH monitoring, by verifying the source of alkaline reflux into the esophagus had advantage of better quantifying alkaline reflux over single pH monitoring. AGER might be more frequent in pediatrics than adults.

Alkalosis↗
PubMed1990

[Acidic stimulation of esophageal peristalsis: its prognostic value in reflux].

Gastroesophageal Reflux (GER) in children manifests itself by several clinical pictures. Its diagnosis is difficult and so are surgical indications. The search for prognostic parameters able to predict the need for surgery are therefore warranted. We have demonstrated in previous studies in children with GER a decrease in propulsive peristalsis and an increase in non-propulsive activity. We have also reported that patients able to respond to medical treatment correct their motor trouble when acid is instilled into the esophagus, whereas those unable to respond to it do not. Aiming at clarifying the prognostic value of this acid challenge test we have thus measured Esophageal Motor Efficiency (EME) (prop. waves/h multiplied by mean pressure) in basal conditions and after acid challenge in 52 children divided into two groups according to their response to medical treatment during periods exceeding 6 months. EME in basal conditions did not allow differentiation between both groups, but EME after acid challenge did so. Optimum threshold value was 565, sensitivity 0.76, specificity 0.75, positive predictive value 87%, and negative predictive value 60%. This test seems to have some prognostic value in pediatric GER.

Child↗
PubMed1989

[Peristalsis induced in normal esophagus and gastroesophageal reflux].

We have investigated manometrically wether esophageal motor response (in terms of frequency and mean pressure of propulsive and non-propulsive waves) to the instillation of saline and 0.1 N HCl into the lumen was different in normal (n = 18) and refluxing (n = 66) patients. Instillation of saline induced bursts of non-propulsive waves both in normal and refluxing patients. Additionally, it induced in the latter an increase in propulsive waves. Instillation of acid did not induce in normal subjects changes different from those generated by saline but stimulated considerably the refluxing esophagus which responded with an increased number of more powerful waves. This results suggest that refluxing esophagus is hypocontractile as compared with the healthy one and that it is awaken by acid as if it tried to improve its motor efficiency.

Adolescent↗
PubMed1986

[Gastroesophageal reflux in neurologic patients].

Sixteen among the 129 children operated upon for GER in the last 9 years had neurologic diseases with psychomotor retardation. Average age at diagnosis was advanced (90 months) although most patients vomited since infancy and more than 50% had haemorrhage as a sign of oesophagitis which was endoscopically confirmed in 10 cases. Prolonged acid exposure as proven by extended pH-metry was due to motor failure with incompetence of the LES and abnormal peristalsis (aside with other minor factors) as we could demonstrate manometrically. Surgical treatment achieved good results in almost all cases and we think that there is no reason not to offer its benefits to this group of patients. GER is more frequent and severe in brain damaged patients than it can be judged by the scarce number of them operated upon in our country. It must be looked after in them and treated appropriately whenever complications make it advisable.

Adolescent↗
PubMed1986

[Functional study of gastroesophageal reflux in children with brain diseases].

Aiming to evaluate the participation of oesophageal motor troubles in the pathogeny of gastro-oesophageal reflux in brain-damaged children, we have studied 16 of these patients. Most of them had a more or less severe esophagitis due to excessive acid exposure. We have found a decreased LESP as compared to normal subjects (8.84 +/- 6.20 vs. 18.33 +/- 6.55 mmHg (p less than 0.001)), and high percentages of non-propulsive waves in basal conditions (70 +/- 29.66 vs. 6.25 +/- 9.16 (p less than 0.001)) as well as after serum (66.33 +/- 28.06 vs. 16.66 +/- 13.66 (p less than 0.001) and acid instillation (58.33 +/- 28.91 vs. 26.41 +/- 12.04 (p less than 0.05)). These results demonstrate that motor disturbances are responsible for the severity of GER in this group of patients.

Adolescent↗