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Biomedical subjects

E Jimenez

Publications and source records attributed to E Jimenez.

At least 73 records · Page 4Linked to original sources
PubMed1994

Fura 2 determination of [Ca2+]i in isolated perfused heart using R wave-gated electromechanical shutters.

We describe a novel and relatively inexpensive spectrofluorescence system that supplies rapidly alternating wavelengths to either a standard cuvette or an isolated perfused heart. Its use is illustrated by determining changes in cytosolic intracellular Ca2+ concentration ([Ca2+]i) by using the Ca(2+)-sensitive fluorescent dye fura 2 in a rabbit heart preparation. The system uses two precision electromechanical shutters (capable of gating with respect to the electrocardiographic R wave for signal averaging) allowing alternate fura 2 excitation wavelengths (340 and 380 nm) without moving optical components and uses a fiber optic for conducting excitation and collecting epifluorescence. Sample recordings tracing the [Ca2+]i transient in an entire cardiac cycle and in capturing specific isolated regions (diastole and systole) of the cycle are presented. Limitations of this low-cost but easily implemented system are discussed.

Animals↗
PubMed1994

Angiotensin II receptor subtypes in eel (Anguilla anguilla).

Previous studies have shown the effects of angiotensin II (Ang II) in teleosts, and Ang II-binding sites have also been localized in tissues from rainbow trout. The purpose of this study was to extend these findings and to provide an analysis of Ang II receptor (Ang II-R) isoforms in three tissues obtained from European eel (Anguilla anguilla). Ang II-Rs were identified in eel liver, kidney and intestine membranes by the binding of either 0.5 nmol human 125I-labelled Tyr4-Ile5-Ang II/l or increasing concentrations (1-120 nmol/l) of [3,5-3H]Tyr4-Ile5-Ang II. Using an isoelectric focusing technique, two Ang II-binding sites were identified in liver membranes. These migrated to isoelectric points (pI values) 6.5 and 6.7. Seventy per cent of binding to both sites was displaced by a 10,000-fold excess of unlabelled human Ang II. In both whole plasma membranes and brush border membranes from intestine, only one form of the Ang II-R was found, with pI 6.5 and high affinity (Kd = 3.4 nmol/l) for the [3,5-3H]Tyr4-Ile5-Ang II. Similarly, only the isoform focusing at pI 6.5 was observed in renal tubular epithelial brush border membranes. Reduction of disulphide bridges with dithiothreitol significantly enhanced Ang II binding to the isoform at pI 6.5 in liver (P < 0.05) and kidney (P < 0.01), while in liver the binding to the isoform of pI 6.7 was significantly reduced (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Anguilla↗
PubMed1994

No evidence of developmental III effects of low-level lead exposure in a developing country.

Despite substantial controversy regarding the blood levels at which lead adversely affects neurobehavioral development, public health policy in some industrialized countries is prescribing ever more stringent screening criteria for all ages. This study addressed the question of ill effects of lead exposure at the new lower levels, specifically during the late infancy period, which has been targeted for maximum surveillance in pediatric practice. The sample of 184 participants consisted of 12- to 23-month-old healthy infants and toddlers who participated in a community-based study in a developing Central American country (Costa Rica) where extensive family and developmental information was collected. The mean infant blood lead level was 11.0 micrograms/dL, ranging from 5.4 to 37.0 micrograms/dL. Lead levels were not related to the Mental or Psychomotor Developmental Index of the Bayley Scales of Infant Development. When the children were 5 years old, they were reevaluated with complete physical and psychological testing. Blood lead levels in infancy did not predict any of the developmental outcome measures. Thus, among a group of healthy toddlers in a developing country, no ill effects on development of low blood lead levels were observed.

Anemia, Iron-Deficiency↗
PubMed1993

Comparison of COS cell transfected AT1A and AT1B angiotensin II receptors and angiotensin II receptor isoforms in rat tissues using isoelectric focusing.

Rat adrenal AT1A and AT1B receptors from transfected COS-7 cells were labelled with 125I-Angiotensin II, solubilised, and run on isoelectric focusing gels. Receptors from rat tissues were treated similarly. COS-7 cell-expressed AT1A and AT1B receptors each produced a single peak of specific radioactivity at pI 6.8. Rat liver and rat ovary tissue preparations gave peaks at pI 6.8 and 6.5, respectively. In contrast, rat adrenal tissue preparations gave four peaks at pI 7.0, 6.8, 6.5, and 6.3. The additional isoforms found in the rat adrenal tissue preparations may represent post-translationally modified or novel receptors.

Adrenal Glands↗
PubMed1993

Detection of bovine leukemia virus RNA in serum using the polymerase chain reaction.

A method was developed for detecting bovine leukemia virus (BLV) RNA in serum samples using a pair of primers from the BLV polymerase gene in the polymerase chain reaction (PCR). The PCR was able to detect 3800-7600 molecules of BLV RNA. At this level of sensitivity eleven pools of adult and one fetal bovine serum appeared free from BLV contamination.

Animals↗
PubMed1993

Central nervous system alterations in a case of short-rib polydactyly syndrome, Majewski type.

The authors present a case of CNS abnormalities in a female newborn infant with Majewski syndrome. On examination the gyri were found to be normal, but there was narrowing of the corpus callosum and fornix, and dilated ventricles. A vermis hypoplasia and an arachnoid cyst were found between the cerebellar hemispheres. Cross-section of the cervical and thoracic segments revealed a flattened spinal cord in the sagittal section. There were reactive astrocytes and heterotopic ganglion cells in the white matter and isolated hypoxically damaged nerve-cells in the subiculum and nuclear masses of the brainstem. These findings are discussed with reference to the literature.

Brain↗
PubMed1993

Redistribution of myocardial calcium during ischemia. Relationship to onset of contracture.

Cytosolic calcium accumulation has been proposed as a mediator for the pathologic changes that occur during myocardial ischemia. Whether the rise in cytosolic calcium is a result of influx or redistribution from internal stores has not been elucidated. Isolated retroperfused rabbit hearts were subjected to ischemia at 37 degrees C. The distribution of calcium between cytosol and internal membrane stores and the relationship between cytosolic calcium and the onset of left ventricular contracture were investigated. One group of hearts was loaded with the fluorescent calcium probe Fura 2-AM to measure cytosolic calcium and a second group with chlortetracycline to indicate changes in membrane-bound calcium. After the onset of ischemia there is a rise in cytosolic calcium, at least in part attributable to redistribution of calcium from intraorganellar sites to cytosol. The release of membrane-bound calcium and rise in cytosolic calcium preceded the onset of irreversible ischemic injury, that is, contracture.

Animals↗
PubMed1992

Characterization of postsynaptic alpha-adrenoceptors in the arteries supplying the oviduct.

1. In vitro experiments were designed to characterize postjunctional alpha-adrenoceptor subtypes in ring segments (1 mm length; outer diameter 300-500 microns) from arteries supplying the oviduct of the heifer. 2. Noradrenaline, adrenaline and phenylephrine evoked concentration-dependent contractile responses. The pD2 values were 5.67, 5.89 and 5.93, respectively. Medetomidine clonidine and B-HT 920 (2-amino-6-allyl-5,6,7,8-tetra-hydro-4H-(thiazo)-4,5-d-azepoine ) were ineffective. 3. The alpha-adrenoceptor selective antagonists, prazosin (1 nM-0.1 microM) and rauwolscine (0.1-10 microM) competitively antagonized the response to noradrenaline. The pA2 values were 9.38 and 6.83, respectively. 4. The dissociation constant (KD) for noradrenaline calculated by use of the irreversible antagonist, dibenamine, was 3.95 (2.09-5.81) microM. The occupancy-response relationship was non-linear. Half-maximal response to noradrenaline was obtained with 22% receptor occupancy while maximal response required 100% occupancy. 5. B-HT 920 evoked a biphasic contractile concentration-dependent response in preparations incubated in a physiological solution containing 20 mM K+, 0.1 microM prazosin and 1 microM propranolol. Rauwolscine 0.1 microM significantly (P less than 0.01) blocked the first component of the B-HT 920 concentration-response curve with an apparent pA2 value of 8.52 (7.86-9.18). 6. These results strongly suggest that alpha-adrenoceptors in oviductal arteries are mainly of the alpha 1 subtype, although a possible role for alpha 2-adrenoceptors cannot be excluded.

Acetylcholine↗
PubMed1992

Relationship of utero- and fetoplacental blood flow velocity wave forms with pathomorphological placental findings.

Pulsed Doppler examinations were performed in 143 risk pregnancies. The resistance index (RI) values of the uteroplacental vessels and umbilical artery on the last examination before delivery were correlated to specific patterns of morphological placental findings. The sensitivity and specificity of Doppler blood flow velocity wave forms to predict placental disease as well as the significant relationships were calculated. Impaired uteroplacental perfusion is correlated with: disturbances in growth, such as reduced weight and reduced basal area (p < 0.005, p < 0.05); disturbances in villous maturation, such as prematurity or a reduction in intermediate sized villi (p < 0.05, p < 0.01), and circulation disorders, such as acute or chronic infarcts (p < 0.05), villous fibrosis (p < 0.005) or microfibrin deposits (p < 0.05). Villous immaturity was not correlated to either pathological utero- or fetoplacental blood flow. Except for acute infarcts, all these findings as well as endangiopathy of truncal arteries are also combined with high RI values in umbilical arteries (p < 0.005) possibly reflecting the 'down-stream impedance' of the fetoplacental circulation.

Blood Flow Velocity↗
PubMed1992

Effect of aging on intracellular Ca2+, pHi, and contractility during ischemia and reperfusion.

BACKGROUND: To investigate the effect of aging on myocardial ischemic and reperfusion injury, cytosolic calcium (Ca2+), intracellular pH (pHi), and mechanical performance were measured in isolated perfused rabbit hearts. METHODS AND RESULTS: Hearts of mature (4-5-month-old) and aged (28-38-month-old) rabbits were loaded with 10 microM of fura-2 or 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) and subjected to 30 minutes of normothermic ischemia and reperfusion. Cytosolic Ca2+ levels ([Ca2+]) during the nonbeating ischemic period and end-diastolic Ca2+ levels ([EDCa2+]) during reperfusion were determined from the fura-2 fluorescence ratio of emission at 510 nm during excitation at 340 and 380 nm. pHi was obtained from the ratio of emission at 530 nm during excitation at 450 and 490 nm. [Ca2+] of the mature group (n = 8) increased from 188 +/- 19 nM (mean +/- SEM) to 373 +/- 32 nM during ischemia, and that of the aged group (n = 7) increased from 242 +/- 17 to 465 +/- 20 nM. The rise of [Ca2+] of the aged group was significantly greater (p < 0.05) than that of the mature group. Immediately after reperfusion, [EDCa2+] in both groups returned to the preischemic level. pHi decreased to the same extent (from 7.2 to 6.7) during ischemia and returned to preischemic values during reperfusion. The mature group recovered 84 +/- 3% of left ventricular peak pressure after ischemia, whereas the aged group recovered only 55 +/- 3% (p < 0.005). Functional recovery was inversely correlated to the increase of [Ca2+] during ischemia (r = 0.66). CONCLUSIONS: Aged hearts exhibit greater accumulation of [Ca2+] during ischemia and less functional recovery after ischemia than mature hearts. The greater rise of [Ca2+] in aged hearts is not a result of the difference of buffering capacity for ischemia-induced acidosis.

Aging↗
PubMed1992

Age-related differences in cardiac susceptibility to ischemia/reperfusion injury. Response to deferoxamine.

Age-related differences in susceptibility to ischemia/reperfusion injury and the response to the iron chelator deferoxamine during reperfusion were studied in isolated nonworking rabbit hearts subjected to 30 or 40 minutes of ischemia at 37 degrees C followed by 30 minutes of reperfusion. In the experimental group, hearts received a bolus of deferoxamine just before the moment of reflow, followed by a continuous infusion during the first 10 minutes of reperfusion. Isovolumic systolic (peak developed pressure) and diastolic (diastolic pressure versus balloon volume relationship) function was assessed with an intracavity balloon and incremental volume changes. In separate groups of hearts, adenine nucleotide content (adenosine triphosphate, diphosphate, and monophosphate) was measured before ischemia, at end-ischemia, and 30 minutes after reperfusion. The cardiac function measurements showed that after 30 minutes of ischemia and 30 minutes of reperfusion, peak developed pressure in newborn hearts recovered to 89% +/- 5% of preischemic levels; this recovery was significantly better than that of adult hearts, which exhibited 67% +/- 6% (p less than 0.01) recovery. Deferoxamine significantly improved cardiac function only in adult hearts (p less than 0.01). However, after 40 minutes of ischemia and 30 minutes of reperfusion, peak developed pressure in newborn hearts was reduced to 61% +/- 3% and was not significantly better than that of adult hearts (54% +/- 5%). Deferoxamine significantly improved systolic function in both newborn and adult hearts (p less than 0.01) exposed to 40 minutes of ischemia. Myocardial adenosine triphosphate content fell markedly by the end of 30 and 40 minutes of ischemia in both groups. After 30 minutes of ischemia, newborn but not adult hearts were able to completely recover adenosine triphosphate content by 30 minutes of reperfusion. This advantage was lost after 40 minutes of ischemia. Deferoxamine had no effect on recovery of adenosine triphosphate content in any group. We conclude that (1) newborn hearts recover postischemic function and metabolism faster than adult hearts after shorter periods of ischemia; (2) this advantage is lost as the ischemic period is prolonged; (3) deferoxamine improved postischemic cardiac function after longer ischemic periods, in both age groups, but failed to improve the recovery of myocardial adenosine triphosphate content.

Adenine Nucleotides↗
PubMed1991

Long-term developmental outcome of infants with iron deficiency.

BACKGROUND: Iron-deficiency anemia has been associated with lowered scores on tests of mental and motor development in infancy. However, the long-term developmental outcome of infants with iron deficiency is unknown, because developmental tests in infancy do not predict later intellectual functioning. METHODS: This study is a follow-up evaluation of a group of Costa Rican children whose iron status and treatment were documented in infancy. Eighty-five percent (163) of the 191 children in the original group underwent comprehensive clinical, nutritional, and psychoeducational assessments at five years of age. The developmental test battery consisted of the Wechsler Preschool and Primary Scale of Intelligence, the Spanish version of the Woodcock-Johnson Psycho-Educational Battery, the Beery Developmental Test of Visual-Motor Integration, the Goodenough-Harris Draw-a-Man Test, and the Bruininks-Oseretsky Test of Motor Proficiency. RESULTS: All the children had excellent hematologic status and growth at five years of age. However, children who had moderately severe iron-deficiency anemia as infants, with hemoglobin levels less than or equal to 100 g per liter, had lower scores on tests of mental and motor functioning at school entry than the rest of the children. Although these children also came from less socioeconomically advantaged homes, their test scores remained significantly lower than those of the other children after we controlled for a comprehensive set of background factors. For example, the mean (+/- SD) adjusted Woodcock-Johnson preschool cluster score for the children who had moderate anemia in infancy (n = 30) was 448.6 +/- 9.7, as compared with 452.9 +/- 9.2 for the rest of the children (n = 133) (P less than 0.01); the adjusted visual-motor integration score was 5.9 +/- 2.1, as compared with 6.7 +/- 2.3 (P less than 0.05). CONCLUSIONS: Children who have iron-deficiency anemia in infancy are at risk for long-lasting developmental disadvantage as compared with their peers with better iron status.

Anemia, Hypochromic↗
PubMed1991

Hormonal changes associated with bleeding during low dose progestogen contraception delivered by Norplant subdermal implants.

The main side effect associated with the use of Norplant contraceptive implants is a disruption of the menstrual bleeding pattern. To explore the relationship between bleeding and hormonal changes, we analyzed the estradiol (E2) and progesterone (P) patterns that preceded bleeding episodes or that corresponded to periods of amenorrhea in 103 cycles observed among 82 women using Norplant subdermal implants. Five different bleeding patterns were defined: 'normal' (24-45 day cycles), oligomenorrhea (46-90 day cycles), amenorrhea (over 90 day cycles), irregular/frequent bleeding (less than 25 day cycles), and prolonged bleeding (continuous bleeding/spotting for more than 10 days). All 'normal' cycles were associated with a rise followed by a fall in E2 levels preceding bleeding. In half of the 'normal' cycles (28/54), a rise and fall of P was also observed. The same pattern was found in oligomenorrheic cycles, but only two of 12 cycles had a rise and fall of both E2 and P. None of the subjects with amenorrhea had luteal activity. Six of the nine amenorrheic cycles displayed persistently low E2 levels (below 75 pg/ml). The remaining three had a moderate elevation in E2 levels during the sampling period. Sixty percent of the subjects who showed irregular/frequent bleeding (15/25) had low E2 levels (less than 75 pg/ml), without luteal activity, and bleeding occurred without clear evidence of a further drop in E2 levels. In the remaining 40%, bleeding was preceded by a rise and drop of E2 without luteal activity, with the exception of one women, who exhibited a rise and fall of both E2 and P. Samples were obtained in only three subjects during continuous bleeding. One had low E2 levels, and the remaining two bled continuously, in spite of having E2 levels in the normal range. We conclude that ovarian hormones continue to influence endometrial shedding during the use of Norplant contraceptive implants.

Amenorrhea↗
PubMed1991

Multiple forms of angiotensin II receptors in rat tissues.

Angiotensin II (AII) receptors were identified in rat tissue membranes by specific binding of 125I-labelled AII. Using an isoelectric focusing technique, two forms of the high-affinity AII receptor were identified in rat adrenal zona glomerulosa and liver membranes. These migrated to isoelectric points (pI) 6.8 and 6.7. Two low-affinity forms migrated to pI 6.5 and 6.3. The two high-affinity forms were in greatest abundance in the zona glomerulosa, while the low-affinity pI 6.5 isoform was predominant in liver membranes. In uterine membranes both low-affinity isoforms were observed, but there was only one of the high-affinity forms (pI 6.7). Concentrations of AII receptor isoforms were increased in the zona glomerulosa of sodium-deprived rats. Reduction of disulphide bridges with dithiothreitol (DTT) had different effects on the various AII receptor isoforms. Thus 1 mmol DTT/1 caused a twofold increase in 125I-labelled AII binding in zona glomerulosa membranes. DTT produced no appreciable differences in specific AII binding in uterine membranes, whereas there was a 50% reduction of binding in liver membranes. At 20 mmol/l, DTT greatly decreased AII binding in all tissues. The data suggest the existence of multiple forms of AII receptors which may have different functions.

Animals↗