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Biomedical subjects

M Echevarría

Publications and source records attributed to M Echevarría.

At least 19 recordsLinked to original sources
PubMed2003

Jugular vein and carotid artery blood flow in fetuses with increased nuchal translucency at 10-14 weeks' gestation.

OBJECTIVE: The aim of our study was to obtain measurements of the jugular vein and carotid artery pulsatility index (PI) at 10-14 weeks' gestation in chromosomally normal and abnormal fetuses with or without increased nuchal translucency (NT), in order to explore whether a relationship exists between increased NT and overperfusion of the head. METHODS: This was a prospective study involving 179 pregnant women at high risk for chromosomal anomalies or structural malformations who were referred for chorionic villus sampling or first-trimester ultrasound examination at 10-14 weeks' gestation, respectively. Color and pulsed Doppler ultrasound were used to obtain jugular vein and carotid artery blood flow velocity waveforms at the level of the mid-neck. All Doppler measurements were obtained by a single investigator. The PIs of the jugular vein and carotid artery were correlated with NT measurement and fetal karyotype. RESULTS: Doppler measurements of the jugular vein and carotid artery were successfully obtained in 90.5% of the fetuses. The fetal karyotype was abnormal in 13 cases, including three trisomies 21 and two trisomies 18, and normal in 149 cases. In the group with normal karyotype the NT was above the 95th percentile in 22 cases (15%). No correlation between the jugular vein or the carotid artery PI and the thickness of the NT was found. There were no significant differences when comparing the values of the jugular vein and carotid artery PI between the group with normal NT and the group with increased NT, or between the group with a normal karyotype and an abnormal karyotype. CONCLUSION: Our results suggest that NT is not related to blood flow impedance in either the carotid artery or the jugular vein. Overperfusion and venous congestion of the head do not appear to be a causative pathophysiological mechanism involved in increased NT.

Adult↗
PubMed2001

Identification of a new water channel (Rp-MIP) in the Malpighian tubules of the insect Rhodnius prolixus.

Malpighian tubules (MT) of Rhodnius prolixus transport fluid at very high rates. To identify whether aquaporins (AQPs) are present in the MT of R. prolixus, total ribonucleic acid (RNA) was isolated from MT and used in a reverse transcription, polymerase chain reaction (RT-PCR), with two degenerate primers to highly conserved regions of the members of the AQPs family. A deoxyribonucleic acid (DNA) fragment of 370 bp was amplified; its sequence revealed a novel protein, representing a new member of the major intrinsic protein (MIP) family. The complementary DNA (cDNA) sequence of this new MIP protein was cloned by using RNA from MT and the rapid amplification of cDNA ends (RACE) technique. The cDNA had 1133 bp and the largest open reading frame coded for a protein of 286 amino acids, named R. prolixus major intrinsic protein (Rp-MIP). The hydrophobicity profile of the amino acid sequence predicts six transmembrane domains. Northern blot analysis of MT RNA showed a single transcript of about 1-1.3 kb for Rp-MIP. RT-PCR of single isolated MT and in situ hybridization analysis showed Rp-MIP transcripts in both proximal and distal segments. Expression of Rp-MIP in Xenopus laevis oocytes doubled the osmotic water permeability Pf, indicating that Rp-MIP may function as an aquaporin protein in the MT of the insect and thus may participate in urine formation in R. prolixus.

Amino Acid Sequence↗
PubMed2001

The role of ductus venosus blood flow assessment in screening for chromosomal abnormalities at 10-16 weeks of gestation.

OBJECTIVE: To evaluate the role of ductus venosus blood flow assessment at 10-16 weeks' gestation in screening for chromosomal abnormalities. METHODS: Ductus venosus blood flow was prospectively evaluated in 1371 consecutive pregnancies between 10 and 16 weeks of gestation. The pulsatility index for veins was calculated. All cases were screened for chromosomal defects combining maternal age and fetal nuchal translucency thickness. RESULTS: A chromosomal abnormality was found in 20 cases. The overall detection rate, specificity, positive predictive value, negative predictive value and odds ratio for chromosomal abnormalities were 65%, 95.7%, 18.3%, 99.5% and 41 (95% CI 16-108), respectively, when using the 95th centile pulsatility index as a cut-off. CONCLUSIONS: These preliminary results suggest that evaluation of the ductus venosus pulsatility index at 10-16 weeks' gestation is a useful second-line screening test for chromosomal defects. A combination of nuchal translucency measurement and ductus venosus assessment might increase specificity while maintaining an optimal detection rate for chromosomal abnormalities. Such a policy could identify 55% of all chromosomal abnormalities and about 69% of autosomal trisomies, reducing the need for invasive testing to less than 1%.

Adult↗
PubMed2001

[The efficacy and safety of continuous epidural analgesia versus intradural-epidural analgesia during labor].

OBJECTIVE: To determine the efficacy and safety of intradural-epidural analgesia in comparison with continuous epidural analgesia during labor and childbirth. PATIENTS AND METHOD: Forty-two women whose labor began spontaneously were enrolled and distributed randomly in two groups. The intradural-epidural analgesia group (IEA, n = 21) received 25 microgram of intradural fentanyl with 2.5 mg of isobaric bupivacaine with adrenalin, after which analgesia was maintained with epidural administration of one 8 mL bolus of 0.125% bupivacaine, followed by perfusion of a balanced concentration at a rate of 8 ml/h. Patients in the continuous epidural analgesia group (CEA, n = 21) were given 8 ml of 0.25% bupivacaine with adrenalin; the epidural perfusion of 0.125% bupivacaine and 1 microgram/ml of fentanyl was started at the same rate as in the IEA group. We recorded pain as assessed on a visual analog scale, extension of sensory and motor block, maternal hemodynamic constants, number of boluses of bupivacaine used, total doses of bupivacaine and oxytocin, instruments needed for childbirth, and side effects (pruritus, nausea and vomiting). RESULTS: Analgesic efficacy during the first 30 minutes was greater in the IEA group. The total dose of bupivacaine, required top-up boluses, and the extension of sensory block at 30 minutes, one hour and two hours were also significantly less in the IEA group. The incidence of pruritus was higher in the IEA group. No significant differences were observed for other variables. CONCLUSIONS: Intradural-epidural analgesia provides effective analgesia for labor, with rapid onset, reduced extension of sensory block, lower total doses of local anesthetics and few side effects.

Adult↗
PubMed2001

[Influence of bispectral index monitoring on fentanyl requirements during total intravenous anesthesia for major gynecological surgery].

OBJECTIVE: To determine the influence that bispectral index (BIS) monitoring of hypnosis might have on need for analgesia during surgery under total intravenous anesthesia provided by bolus administration of fentanyl. PATIENTS AND METHOD: Prospective, randomized and partially double-blind study of 40 patients undergoing major gynecological surgery under total intravenous anesthesia with propofol and fentanyl. In the BIS group (n = 20) propofol administration was adjusted to maintain BIS between 40 and 60. In the control group (n = 20) standard doses were given: 10 mg/kg-1/h-1 after anesthetic induction and for 5 minutes, 8 mg/kg-1/h-1 over the next 5 minutes and 6 mg/kg-1/h-1 throughout the rest of the operation. All patients received intravenous bolus administration of 150 or 75 microg of fentanyl to maintain analgesia whenever systolic blood pressure and heart rate increased 20% over baseline. We compared propofol and fentanyl requirements, intraoperative changes in BIS, and awakening from anesthesia. RESULTS: Patient and surgical characteristics were similar in both groups. BIS monitoring allowed propofol administration to be decreased a mean 24% during maintenance of anesthesia, and this in turn was associated with a significant increase in mean dose of fentanyl (415 microg versus 253 microg in the BIS and control groups, respectively; p = 0.01). Mean values of BIS were higher in the BIS group (46.4 versus 42.2; p = 0.04) and patients in the BIS group awoke sooner (in 7.7 min versus 11.1 min; p = 0.01) and tended to report less pain upon arrival at the postanesthetic recovery room, although the difference was not statistically significant. CONCLUSIONS: BIS monitoring of depth of hypnosis can influence requirements for fentanyl during total intravenous anesthesia by bolus dosing for maintenance of analgesia. This is probably due to changes in the administration of propofol made possible by BIS monitoring.

Adult↗
PubMed2000

Nuchal thickness evolution in trisomy 18 fetuses.

OBJECTIVE: To assess the natural evolution of nuchal thickness in trisomy 18 fetuses. METHODS: Serial measurements of nuchal thickness were performed over a 1- to 5-week period in 17 fetuses with trisomy 18, from the 10th to the 20th week of pregnancy. To avoid a confounding effect due to gestational age, nuchal thickness was also expressed in standard deviations (SD) for the corresponding gestational week. In addition, the changes were assessed in terms of the presence of clinically positive thickening, considered as such when its measurement was above 2.5 SD for the corresponding gestational week. RESULTS: On the initial nuchal thickness measurement, sensitivity for trisomy 18 decreased from 66% on assessment at 10-13 weeks of gestation to 38% at 14-16 weeks. In serial determinations, a mean increase of 1.3 mm [95% confidence interval (CI), 0.1-2.5] was observed for a mean period of 21 days. When corrected for gestational age, the mean increase of 0.2 SD (95% CI, -1.2 to -1.6) was found to be non-significant. No clinically relevant changes were recorded on re-examination, with nuchal thickening remaining stable in 76% of cases. CONCLUSION: Nuchal thickening at re-examination was observed in a similar proportion of trisomy 18 fetuses as when initially observed.

Adult↗
PubMed1999

Differential upregulation of aquaporin-4 mRNA expression in reactive astrocytes after brain injury: potential role in brain edema.

Astrocytes and aquaporin-4 (AQP4) play a significant role in brain ion homeostasis. Consequently the regulation of AQP4 mRNA in the CNS after different neurological insults was of interest. A single intrastriatal injection of ringer or quinolinic acid strongly induced AQP4 mRNA in the striatum, specially at the core of the lesion. Colocalization studies demonstrated that AQP4 mRNA induction was restricted to hypertrophic astrocytes. The extent of striatal AQP4 mRNA induction did not correlate with neuronal degeneration, but it did with extravasation of Evans blue dye as a marker of BBB disruption. Distant lesions were additionally induced by either 6-OHDA or a knife cut in the medial forebrain bundle (MFB). The former, but not the latter, induced a high AQP4 mRNA expression in the lesioned substantia nigra. However, axotomy of the MFB induced a high AQP4 mRNA expression at the lesion site. We conclude that the induction of AQP4 mRNA expression is related to disruption of the blood-brain barrier and under brain edema conditions this water channel plays a key role in the reestablishment of the brain osmotic equilibrium.

Animals↗
PubMed1999

Localization of aquaporin-3 mRNA and protein along the gastrointestinal tract of Wistar rats.

Since specific proteins responsible for water transport (aquaporins, AQPs) have been identified in a great variety of tissues, we decided to study the presence of AQP3 in the gastrointestinal tract (GIT) of Wistar rats. Poly(A+) RNA was purified from the mucosa of the stomach, jejunum, ileum and colon, and gross detection of AQP3 mRNA was done by Northern blot analysis. In situ hybridization studies were carried out to precisely localize the distribution of this transcript. Sections of the different tissues were hybridized with @400-bp [35S]riboprobes. The results presented here demonstrate that AQP3 is expressed throughout the GIT, with its expression in the colon and ileum greater than that in the stomach. Immunohistochemistry experiments, using a polyclonal antibody against AQP3, revealed that AQP3 protein is present at the basolateral membrane of the epithelial cells lining the villus tip of the small intestine and colon. The finding of AQP3 in the intestinal epithelia strongly suggests that this protein functions as a pathway for water transport in this epithelium.

Animals↗
PubMed1999

Biochemical markers of bone turnover after surgical menopause and hormone replacement therapy.

The objective of this study was to evaluate the effect of surgical menopause and hormone replacement therapy (HRT) on the new biochemical markers of bone turnover. Fourteen women who had undergone surgical menopause and began HRT 3 months after surgery were recruited for a 1-year study. Results were compared with a control group of 31 healthy premenopausal women of similar age. Serum samples were obtained to determine total alkaline phosphatase, bone alkaline phosphatase, propeptides carboxy- and amino-terminal of type I procollagen (PICP, PINP), osteocalcin, tartrate-resistant acid phosphatase, and carboxy-terminal telopeptides of type I collagen (ICTP and serum CTX). Urine samples were analyzed for hydroxyproline, pyridinoline, deoxypyridinoline, alpha- and beta-carboxy-terminal telopeptides of type I collagen (alpha-CTX and beta-CTX), and amino-terminal telopeptide of type I collagen (NTX). Determinations were performed after 3 months of surgical menopause and after 3 and 9 months of HRT. All biochemical markers increased after menopause, and most of them normalized after 9 months of HRT. Serum PINP showed the highest proportion of increased values after surgery among bone formation markers (62%), as well as the highest mean percent increase (101%). Among bone resorption markers in postmenopausal women, urinary beta-CTX, alpha-CTX, NTX, and serum CTX showed the highest proportion of increased values (100%, 67%, 58%, 58%, respectively) as well as the greatest mean percent increase. They were also the markers with the most marked response to HRT. In conclusion, serum PINP is the most sensitive marker of bone formation, whereas beta-CTX is the most sensitive marker of bone resorption after surgical menopause. In addition, both markers showed the highest response after HRT.

Acid Phosphatase↗
PubMed1998

Fetal heart rate and nuchal translucency in detecting chromosomal abnormalities other than Down syndrome.

OBJECTIVE: To evaluate whether the combined use of fetal heart rate (FHR) and nuchal translucency measurements would be useful in the prediction of fetal chromosomal abnormalities at 10-13 weeks' gestation. METHODS: In a prospective study, 1053 (553 reported previously) consecutive singleton pregnancies between 10 and 13 weeks' gestation underwent chorionic villus sampling at our institution. Fetal heart rate and fetal nuchal translucency thickness were measured immediately before the invasive procedure. RESULTS: Thirty-five abnormal karyotypes were diagnosed, including 17 trisomy 21, seven trisomy 18, one trisomy 13, one trisomy 9, four unbalanced translocation, two Klinefelter syndrome, one Turner syndrome, one deletion of chromosome 18, and one true mosaicism. Using 95% of normal ranges as the cutoff for both measurements, the detection rate for all chromosomal anomalies was 77.1%, with a false-positive rate (1-specificity) of 7.7%, a positive predictive value of 25.7%, and a negative predictive value of 99.2%. Fetal heart rate improved the sensitivity of nuchal thickness in trisomies 21 and 18 (from 62.5% to 75%) and was particularly useful to detect other chromosomal anomalies (from 27.2% to 81.8%). CONCLUSION: Our findings suggest that there is an added role of FHR in ultrasound screening of chromosomal abnormalities, specifically for those other than trisomy 21 and 18. The value of a single measurement of fetal heart rate for screening purposes needs to be confirmed by further investigation in a low-risk population.

Adult↗
PubMed1998

[Satisfaction with locoregional anesthesia in women who had undergone cesarean section].

OBJECTIVES: To compare satisfaction with local-regional and general anesthesia in women undergoing cesarean, the possible influence of time of evaluation and recall of the anesthesiologist. PATIENTS AND METHODS: Retrospective study performed in all women who delivered by cesarean in the 6 first months of 1997. The women were assigned to two groups according to type of anesthesia, local-regional or general. Their satisfaction with anesthesia was evaluated by questionnaire 48 to 72 hours after surgery and two weeks after release. Most items required discrete-point answers, including a satisfaction of a scale of 0 to 10. During the second interview we also evaluated satisfaction with the procedure and hospital in general, as well as recall of the anesthesiologist. Group homogeneity was based on demographic, sociocultural, obstetric and surgical variables. RESULTS: In a context of high satisfaction with anesthesia, 189 (76%) of the 247 women receiving local-regional anesthesia gave high evaluations to the anesthesia (8.90 +/- 1.5; mean: 10), compared with 58 (24%) of those receiving general anesthesia (8 +/- 2; mean 8.5) (p = 0.001). Both groups were homogeneous except for the distribution of emergencies, which occurred more often in those receiving general anesthesia (p < 0.001). Women who had received local-regional anesthesia expressed greater willingness to repeat or recommend the technique (p < 0.001). The highest score in this group was from women receiving intradural anesthesia along with fentanyl for local anesthesia, with significant differences only in comparison to epidural anesthesia. The differences in responses between the first and second interview were scarce. The hospital received a lower evaluation than did either anesthesia or surgery (p < 0.001). The anesthesiologist, who was less well recognized than the obstetrician was remembered better among women receiving local-regional anesthesia (p = 0.008). CONCLUSIONS: Local-regional anesthesia can improve levels of satisfaction over that of general anesthesia among women undergoing cesarean surgery, and contributes to maintaining recall of the anesthesiologist. These results may be related to the fact of being conscious during the birth of a child.

Adolescent↗
PubMed1998

Aquaporins.

Aquaporins (AQP) are members of the major intrinsic protein superfamily of integral membrane proteins, which function as specialized water channels to facilitate the passage of water through the cell membrane in animals, plants and bacterias. Ten AQP homologues named from 0 to 9 have been clones so far in mammals. They are widely distributed and more than one AQP could be present in the same cell. Most of the AQPs are only permeable to water and impermeable to small organic and inorganic molecules, except for AQP 3, 7 and 9 which are also permeable to urea and glycerol. From the hydrophobicity profile all AQPs seem to have six transmembrane domains with five connecting loops and with the amino and carboxyl termini in the cytoplasm. They are synthesized as monomers, but there is evidence suggesting that AQPs are formed in the membrane as tetrameric units, each of which has four water pores. The primary amino acid sequence contains putative phosphorylation sites for protein kinasses A and/or C or casein kinase II, and the expression and membrane protein abundance of some AQPs are known to be under hormonal regulation. The human genes for several AQPs have been cloned and an increasing number of disturbances associated to abnormal functioning of these proteins had been identified.

Aquaporins↗
PubMed1997

Transport of water in proximal kidney tubules from whole tubules to single channels: length and section of the selectivity filter of aquaporin-1.

Proximal straight tubule (PST) were dissected from rabbit kidneys, held with crimping pipettes in a chamber bathed in a buffered mannitol isosmotic solution (MBS, 295 mOsm/kg). Tubule cell volume changes with time (dV/Adt) after steps in MBS osmolality (delta Cs) were monitored on line with an inverted microscope, a TV camera and an image processor. Reflection coefficients sigma and osmotic permeability coefficients, Pos, for several solutes were measured using two methods. Method 1: sigma was calculated from the delta Csiso of impermeant and permeant solutes at which (dV/Adt)t-->0 = 0 (i.e., by a null point method). It is denoted as sigma 1. sigma 1 = 1.00 for mannitol (M), raffinose (R), sucrose (S), glycerol (G), acetamide (A) and urea (U). With formamide (F), sigma 1, Formamide = 0.62 +/- 0.05. These findings confirm our previous value of dp = 4.5 A for the diameter of the selectivity filter of the basolateral PST cell membrane water channel AQP1. Method 2: PST were exposed for 20 s to MBS made hyperosmotic by addition of a delta Cs of 35 mOsm/kg of R, S, M, G, A and U. Cells shrunk within 500 ms of t = 0 to their osmometric volume and remained shrunk for the 20 s of the osmotic challenge. Pos was measured from the shrinking curves. P(os) = 3000 +/- 25 microns/s with R, S, M, G, A and U. Method 2 also allowed to calculate sigma, denoted as sigma 2. sigma 2 = 1.00 for R, S, M, G, A and U. By contrast, the shrinking curve produced by a delta Cs of 35 mOsm/kg F was 1/5th to 1/6th slower and smaller (i.e., subosmometric) than that produced by a delta Cs of 35 mOsm/kg R, S, M, G, A and U. Furthermore, with F cells did not remain shrunk but recovered their original volume within 3 s. P(os) (measured with F) is denoted as P(os)*, P(os)* = 480 +/- 30 microns/s. sigma 2, Formamide = 0.16 +/- 0.01. Use of sigma 1, sigma 2 and P(os)* values in Hill's equations for the bimodal theory of osmosis leads to n = 2-9. Where n is the number of water molecules single filling within the channel selectivity filter, whose length must lie within 6 to 27 A, a value significantly lower than our previous value calculated from the P(os)/Pd* ratio.

Animals↗
PubMed1997

Length of the selectivity filter of aquaporin-1.

We have characterized the selectivity filter of the water channel aquaporin-1 (AQP1) of proximal straight tubules (PST), as an equivalent cylindrical structure with a diameter of approximately 4.5 A, where water molecules single file. We report here efforts to evaluate its length. PST were dissected from rabbit kidneys, held with pipettes in a chamber bathed in a buffered mannitol isosmotic solution (MBS, 295 mOsm/kg). Changes in tubule cell volume with time (dV/Adt), were monitored, on line, with an inverted microscope, a TV camera and an image processor. Osmotic permeability coefficients, Pos, and reflection coefficients (sigma s) were measured with several solutes: mannitol (M), raffinose (R), sucrose (S), glycerol (G), acetamide (A) and urea (U). For this purpose PST were suddenly exposed (in approximately 80 ms and for 20 s) to a hyperosmolality step (delta Cs) achieved by adding to MBS a delta Cs of 35 mOsm/kg of either R, S, M, G, A or U. Cells shrunk within 500 ms of t = 0 to their osmometric volume and remained shrunk for the 20 s of the delta Cs. Pos was measured from the shrinking curves; Pos = 3000 +/- 25 microns/s with either R, S, M, G, A or U. This procedure also allowed to calculate sigma s; sigma s = 1.00 for R, S, M, G, A and U, indicating that these solutes do not penetrate the water channel. In contrast, the shrinking curves produced by a delta Cs = 35 mOsm/kg formamide (F) were 1/5th to 1/6th slower and smaller (subosmometric) than those produced by a delta Cs = 35 mOsm/kg of R, S, M, G, A or U. Furthermore, with F, cells did not remain shrunk. They recovered their original volume within 3 s. Pos (measured with F) is denoted as Pos*; Pos* = 480 +/- 30 microns/s. sigma s, formamide (denoted sigma sp) = 0.16 +/- 0.01. Use of sigma sp and Pos* values in Hill's equations for the bimodal theory of osmosis leads to n = 2-3, n being the number of water molecules single filing within the channel selectivity filter, whose length must lie within 6 to 9 A, a value lower than previous values calculated from the Pos/Pd* ratio.

Animals↗
PubMed1996

Selectivity of the renal collecting duct water channel aquaporin-3.

Aquaporin-3 (AQP3) is a water channel found in the basolateral cell membrane of principal cells of the renal collecting tubule as well as in other epithelia. To examine the selectivity of AQP3, the permeability to water (Pf), urea (Pur), and glycerol (Pgly) of Xenopus oocytes injected with cRNA encoding AQP3 was measured. Oocytes injected with cRNA encoding either human or rat aquaporin-1 (AQP1) were used as controls. Although both aquaporins permit water flow across the cell membrane, only AQP3 was permeable to glycerol and urea (Pgly > Pur). The uptake of glycerol into oocytes expressing AQP3 was linear up to 165 mM. For AQP3 the Arrhenius energy of activation for Pf was 3 kcal/mol, whereas for Pgly and Pur it was >12 kcal/mol. The sulfhydryl reagent p-chloromercuriphenylsulfonate (1 mM) abolished Pf of AQP3, whereas it did not affect Pgly. In addition, phloretin (0.1 mM) inhibited Pf of AQP3 by 35%, whereas it did not alter Pgly or Pur. We conclude that water does not share the same pathway with glycerol or urea in AQP3 and that this aquaporin, therefore, forms a water-selective channel.

4-Chloromercuribenzenesulfonate↗