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Biomedical subjects

R Flores

Publications and source records attributed to R Flores.

At least 109 records · Page 6Linked to original sources
PubMed1991

Plasma catecholamine levels and lipid mobilization induced by yohimbine in obese and non-obese women.

Oral yohimbine administration (0.2 mg/kg) induced lipid mobilization (increase in plasma non-esterified fatty acids, NEFA) in fasting non-obese women (body mass index BMI = 20.2 +/- 0.5, age 35.5 +/- 2.7 years) without significant action on plasma glucose, insulin levels, heart rate or blood pressure during the time-course of the experiment (240 min). Plasma norpinephrine (but not epinephrine) concentrations were increased (100 percent) after oral yohimbine administration. Oral administration of propranolol (40 mg, 60 min before yohimbine) reduced the lipid-mobilizing action of yohimbine (70 percent) during the 60 min following its administration and then totally suppressed its effect until the end of the experimental period (180 min). In fasting obese women (BMI = 36.4 +/- 2.1, age 37 +/- 3.6 years), yohimbine provoked an increase in plasma NEFA levels which was not markedly different from that observed in non-obese subjects. It had no significant effect on plasma glucose, insulin levels, heart rate or blood pressure. Plasma norepinephrine increased in the same proportions. The lipid-mobilizing effect of yohimbine in women is mainly attributable to the increase in synaptic norepinephrine with a resultant increment in lipolysis by beta-adrenergic agonism. In the standard fasting conditions (12 hours) the blockade of the antilipolytic fat cell alpha 2-adrenoceptors seems to be a minor component of the lipomobilizing effect of yohimbine. Morever, when compared with non-obese women, the lipomobilizing effect of yohimbine is not enhanced in obese women.

Administration, Oral↗
PubMed1989

Calcium channels that are required for secretion from intact nerve terminals of vertebrates are sensitive to omega-conotoxin and relatively insensitive to dihydropyridines. Optical studies with and without voltage-sensitive dyes.

Extrinsic absorption changes exhibited by potentiometric dyes have established the ionic basis of the action potential in synchronously activated populations of nerve terminals in the intact neurohypophyses of amphibia and mammals (Salzberg et al., 1983; Obaid et al., 1983, 1985b). Also, large and rapid changes in light scattering, measured as transparency, have been shown to follow membrane depolarization and to be intimately associated with the release of neuropeptides from the nerve terminals of the mouse neurohypophysis (Salzberg et al., 1985; Gainer et al., 1986). We report some experiments that help to define the pharmacological profile of the calcium channels present in intact neurosecretory terminals of vertebrates. For these, we used the peptide toxin omega-conotoxin GVIA (1-5 microM) and the dihydropyridine compounds Bay-K 8644 and nifedipine (2-5 microM), together with the after-hyperpolarization of the nerve terminal action potential. This undershoot depends upon the activation of a calcium-mediated potassium channel, as suggested by its sensitivity to [Ca++]o and charybdotoxin. omega-conotoxin GVIA substantially reduced the after-hyperpolarization in neurosecretory terminals of Xenopus, while neither of the dihydropyridine compounds had any effect under conditions that mimic natural stimulation. The effects of these calcium channel modifiers on the action potential recorded optically from the terminals of the Xenopus neurohypophysis were faithfully reflected in the behavior of the light-scattering changes observed in the neurohypophysis of the CD-1 mouse. omega-conotoxin GVIA (5 microM) reduced the size of the intrinsic optical signal associated with secretion by 50%, while the dihydropyridines had little effect. These observations suggest that the type of calcium channel that dominates the secretory behavior of intact vertebrate nerve terminals is at least partially blocked by omega-conotoxin GVIA and is insensitive, under normal conditions, to dihydropyridines.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1989

Interactions between citrus exocortis and potato spindle tuber viroids in plants of Gynura aurantiaca and Lycopersicon esculentum.

Plants of Gynura aurantiaca and tomato (Lycopersicon esculentum) were inoculated with severe strains of citrus exocortis viroid (CEV) and potato spindle tuber viroid (PSTV). The progeny of both viroids was analyzed by two systems of PAGE which allowed discrimination between CEV and PSTV on the basis of their different sizes. When inoculated separately to G. aurantiaca CEV and PSTV induced severe and very mild symptoms, respectively, with CEV accumulating to a higher level than PSTV, whereas when tomato was the host, each viroid induced severe symptoms (although the reaction caused by PSTV was more intense) with PSTV reaching a higher steady-state concentration than CEV. The simultaneous inoculation of both viroids induced in G. aurantiaca the characteristic symptomatology of CEV, which was the only viroid that could be detected, whereas the response observed in tomato was that typical of PSTV, and only this viroid could be recovered. On the other hand, when G. aurantiaca plants were first inoculated with PSTV and later challenged with CEV, part of the plants displayed the characteristic severe reaction of CEV and both viroids were present in the corresponding extracts, but the other part showed the mild symptomatology induced by PSTV, and only this viroid could be isolated. However, when the protected plants were topped the new shoots exhibited severe symptoms and only CEV could be detected. These results suggest that CEV and PSTV compete for a limiting host factor needed for their replication, transport or accumulation, with CEV and PSTV having the highest affinity for the G. aurantiaca and tomato factors, respectively.

Electrophoresis, Polyacrylamide Gel↗
PubMed1989

Clinical consequences of a human non-fluorescent Y chromosome (Ynf).

A new case of ambiguous genitalia and immature tissue in the left gonad is presented. Cytogenetic findings with various techniques demonstrated that the distal two-thirds of the long arm of the Y chromosome is deleted. Q-banding showed a non-fluorescent Y; three positive bands were however noted when the DA/DAPI technique was applied. After a review of the literature, it was concluded that the non-fluorescent Y chromosome (Ynf) when inherited from generation to generation is a heteromorphism in normal males. However, in our case, where the proband's Y is lacking the fluorescent segment, a simple deletion does not appear to adequately explain the DA/DAPI positive bands. Possibly, a deletion followed by a structural rearrangement of the non-fluorescent segment had occurred de novo. The highly Y-specific DNA sequences present in the fluorescent segment are absent in these patients. The abnormal development in these cases is due to the presence of the 45,X cell line. The gene responsible for spermatogenesis has been localized to the non-fluorescent region in the long arm of the Y chromosome. Furthermore, it is concluded that two types of non-fluorescent Y chromosomes can be found in the population; one is a normal inherent heteromorphic variant, while the other appears to be an abnormality, especially in cases with azoospermia. Such distinctions should clearly be established prior to genetic counseling for patients with so called Ynf or del (Yd).

Chromosome Banding↗
PubMed1988

A double staining method for the detection of a macrophage surface marker and nonspecific esterase activity.

A double staining method for the detection on macrophages of a surface marker (Ia molecules) by immunofluorescence and of non-specific esterase activity is described. This method reveals the co-distribution of both markers in macrophages either fixed in suspension or on coverslips with 1% paraformaldehyde. Good resolution of both markers is obtained and the method should be useful for characterizing mononuclear phagocytic cells in heterogeneous cell preparations.

Animals↗
PubMed1988

Remote prognosis of preeclampsia in women 25 years old and younger.

Twenty-six primiparous women less than or equal to 25 years old who delivered between 1963 and 1978 and met the following criteria were studied: (1) The first obstetric visit was at less than or equal to 30 weeks' gestation with diastolic blood pressure less than or equal to 85 mm Hg; (2) diastolic blood pressure before delivery was greater than or equal to 95-mm Hg, rising at least 15 mm Hg; (3) 24-hour urine protein measured at least 1.0 gm; and (4) patients were enrolled in the Kaiser Health Plan in 1982. Each of the 26 patients was paired with a primiparous woman by year delivered, age, race (black versus nonblack), and weight +/- 1/3. In 23 pairs blood pressure follow-up was available in 1980 or thereafter, which was at least 3 1/2 years after delivery (average interval between delivery and follow-up = 10 years). Three in the preeclampsia group and two in the matched control group had hypertension, with diastolic blood pressure greater than or equal to 90 mm Hg. Mean systolic blood pressure (123.7 mm Hg) was 9.3 mm Hg higher in the preeclampsia group than in the matched controls (114.4 mm Hg), with a standard error of 4.15 mm Hg (p = 0.04). Mean diastolic blood pressure (77.0 mm Hg) was 2.9 mm Hg higher in the preeclampsia group than in the controls (74.1 mm Hg), with a standard error of 3.0 mm Hg (p = 0.345). We conclude that no significant difference in frequency of hypertension or diastolic blood pressure and a small but significant difference in systolic blood pressure is shown in follow-up between patients with preeclampsia and matched controls.

Adolescent↗
PubMed1987

The sequence of a viroid from grapevine closely related to severe isolates of citrus exocortis viroid.

The primary structure of a grapevine viroid (GVs) isolated in Spain was determined. The sequence consisted of 369 nucleotide residues forming a circular molecule. GVs presented extensive homology with viroids of the potato spindle tuber viroid (PSTV) group, that was specially high in the case of citrus exocortis viroid (CEV) both with variants found in isolates inducing severe (92% with CEV-A) and mild (89% with CEV-DE26) symptoms on tomato. The secondary structure proposed for GVs showed that the changes in the sequence in relation to CEV-A generated modifications of the secondary structure particularly important in the left terminal (Tl), variable (V) and pathogenesis (P) viroid domains that have been postulated. Nevertheless it was noted in GVs a central core in the P domain that is conserved in the class A sequence variants characteristic of severe isolates, but not in the class B ones found in mild isolates of CEV. These observations indicate that GVs should be considered as a severe isolate of CEV from grapevine (CEV-g), a suggestion that correlates with the biological properties of CEV-g both in tomato and in Gynura aurantiaca. The presence of this central core in the P domain seems to characterize all the variants of CEV inducing severe symptoms in tomato.

Citrus↗
PubMed1987

Alpha-adrenergic inhibition of rat cerebellar Purkinje cells in vitro: a voltage-clamp study.

1. The effects of the alpha 2-adrenergic agonist clonidine on the membrane properties of Purkinje cells were analysed in sagittal slices of adult rat cerebellum by the use of intracellular recordings performed at a somatic level in the single-electrode voltage-clamp mode. 2. In preliminary current-clamp experiments, clonidine elicited in all cells a hyperpolarization 3-8 mV in amplitude, accompanied by a 15-35% increase of the input resistance when it was added to the bath at a concentration of 2-5 microM. 3. In voltage-clamped cells at a potential of -65 mV. the same concentration of clonidine always induced an outward shift of the holding current (0.2-0.5 nA in amplitude), thus corresponding to the hyperpolarization seen in current-clamp experiments, and this effect was accompanied by a clear increase of membrane resistance. Furthermore, clonidine markedly depressed the inward relaxations induced by hyperpolarizing commands of amplitude less than 10-20 mV whereas those induced by larger steps were much less affected. All these effects of clonidine were reversible when the drug was washed out. 4. When the slices were bathed in a medium containing 10 mM-Cs and 5 X 10(-6) M-tetrodotoxin, the inward relaxations induced by hyperpolarizing steps were abolished. However, a small inward current was still present when the membrane potential was stepped back to -65 mV, which was in turn blocked by the Ca-channel blocker Cd. This inward Ca current was also blocked by 2-5 microM-clonidine in the bath. 5. All these effects of clonidine were abolished by the alpha 1-adrenergic antagonists prazosin and phentolamine at concentrations of 0.5 and 40 microM respectively in the bath. In contrast, they were only weakly antagonized or unaffected by 2 microM of the alpha 2-adrenergic antagonist yohimbine. 6. On the basis of these results and of a previous work on the ionic basis of the inward rectification of Purkinje cells (Crepel & Penit-Soria, 1986), it appears that these neurones exhibit a well developed alpha (possibly alpha 1)-adrenergic inhibition of a low-threshold Ca conductance and a Ca-dependent K conductance operating near resting potential.

Adrenergic alpha-Agonists↗
PubMed1987

[Genetic variability and correlation of yield, grain size, chemical composition and protein quality of 25 varieties of amaranth (Amaranthus caudatus)].

The purpose of the present research was to establish the variability in agronomic, chemical and nutritional characteristics among 25 amaranth (A. caudatus) cultivars. A large variability was found among cultivars in all the parameters evaluated. Average seed weight was 0.75 mg, and had an average size of 1.23 x 1.14 mm. The average moisture, protein and fat content was 11.81, 12.66 and 8.44%, respectively. The average values for methionine, threonine, cystine, leucine and lysine were: 168, 276, 74, 381 and 370 mg/g N, in the same order as presented. It was possible to establish significant, positive correlations between yield-protein, methionine-cystine, methionine-lysine, and threonine-leucine, as well as significant negative correlations between protein-cystine, fat-methionine and cystine- leucine. Furthermore, it is not possible to select cultivars of higher yield on the basis of seed weight, since these two variables were negatively correlated, although not statistically significant. Among all 25 cultivars studied, some were deficient in sulfur-containing amino acids, while based on the FAO/WHO essential amino acid pattern, all of them were deficient in leucine. The average protein quality value expressed as NPR was 3.54 in thermally-processed samples, with no differences between cultivars. Nevertheless, protein digestibility values probably classified the samples in two groups with average values of 79 and 81%, respectively. The variability found can thus be used to select cultivars with higher yields and higher nutritional characteristics.

Amino Acids↗
PubMed1987

[Effect of processing and amino acids supplementation on the protein quality of amaranth (Amaranthus caudatus)].

The present study was undertaken to evaluate the effect of thermic processing on the protein quality of amaranth (A. caudatus). It was also intended to establish the order of essential amino acid deficiencies suggested by the chemical score as limiting protein quality. The A. caudatus grain was cooked in water in the autoclave at 15 lb pressure during 0, 10, 20, 30, 40, 50 and 60 min. Once cooked, the samples were dehydrated with hot air at 60 degrees C and ground into flours. These were analyzed for: tannins, trypsin inhibitors, hemagglutinins (with cow, sheep, and human erythrocytes), damaged starch, available lysine, protein quality (by the NPR method), and true digestibility. Results indicated that the flours (0 to 60 min cooked) did not contain trypsin inhibitors and that their small tannin content, expressed as catechin, disappeared after 30 min of cooking. The quantities of these antiphysiological substances in the raw material are so small that they do not constitute a factor that may cause a decrease of the product's quality. A positive response was obtained for hemagglutinins, stronger with human erythrocytes, which disappeared with cow's and sheep's erythrocytes after 10 min of cooking and with human erythrocytes, after 20 min. As expected, cooking time increased the damaged starch and a slight increase was observed in available lysine, a finding which was impossible to explain satisfactorily. There were no important changes in true protein digestibility with respect to cooking time. Once again, results demonstrated the positive effect thermic treatment had on protein quality, suggesting the presence of antiphysiological active substances or a low nutrient bioavailability in raw samples. Longer cooking times did not alter substantially the protein quality (NPR and digestibility) and it was concluded that 10 min of cooking is an adequate time for the type of processing used. A sample of processed A. caudatus was utilized for the supplementation studies carried out with threonine, methionine, leucine, individually, or with the three amino acids together at 8.0, 9.5 and 1.0% protein in the diet. According to the results obtained, higher NPR values were observed with 9.0 and 9.5% protein content in the diet. No clear effects were detected when the amino acids were added, but there was an interaction between protein in the diet and amino acids. No effect occurred when leucine was added, suggesting that it is not a limiting amino acid. Possibly, threonine is a more limiting amino acid, but the effects were not as high, probably due to the level added to the diets.(ABSTRACT TRUNCATED AT 400 WORDS)

Amaranthus↗
PubMed1986

Detection of citrus exocortis viroid in crude extracts by dot-blot hybridization: conditions for reducing spurious hybridization results and for enhancing the sensitivity of the technique.

Dot-blot assays to detect citrus exocortis viroid (CEV), in clarified sap and unfractionated total nucleic acid preparations of CEV-infected Gynura aurantiaca and chrysanthemum, were impaired by the non-specific binding of the radioactive probe shown by the healthy controls. This non-specific background was considerably reduced by the addition to the hybridization mixture, of the fraction of nucleic acids from healthy plants which are insoluble in 2 M LiCl (containing mainly the large ribosomal RNAs). Sample denaturation with formaldehyde was found to provide a high increase of hybridization, when compared with samples either denatured with formamide or directly spotted. Nitrocellulose was observed to be a better solid support than charge-modified nylon, in terms of the sensitivity of viroid detection by spot hybridization.

Collodion↗
PubMed1986

[Transcutaneous oxygen tension and apnea during sleep stages in normal infants and infants at risk for sudden infant death syndrome].

The relationship between chronic hypoxemia and sudden infant death syndrome (SIDS) has been reported by several authors. In order to study the influence of the apnea-time during a sleep state on transcutaneous oxygen tension (tcPO2), we have studied polygraphically 30 full-term infants (10 controls, 10 SIDS siblings and 10 near-miss for SIDS), aged from 5 to 13 weeks. No significant difference was observed either for apnea-time or tcPO2 between infant-groups studied in different sleep states. We could not find any correlation between apnea-time and tcPO2 in all groups of infants studied during different states of sleep. It is therefore concluded that in normal and at risk for SIDS infants, tcPO2 levels during sleep states cannot be explained only by the apnea-time.

Blood Gas Monitoring, Transcutaneous↗
PubMed1986

Are polygraphic and cardiopneumographic respiratory patterns useful tools for predicting the risk for sudden infant death syndrome? A 10-year study.

Between 1974 and 1984 we have studied 204 control infants (C) comparing them with 650 SIDS siblings (SS) and 146 near-miss for SIDS (NM). These 1,000 full-term infants were recorded by day polysomnography (DPSG; n = 417), night polysomnography (NPSG; n = 257) and cardiopneumography (CPG; n = 2,600). Records were visually analyzed. In DPSG and NPSG, total amount of central, mixed and obstructive apnea as well as the percentage of periodic breathing was studied in each sleep state (active sleep, AS; quiet sleep, QS; indeterminate sleep, IS, and total sleep, TS) and over the total recording time (TRT). In CPG, only the total amount of central apnea and percentage of periodic breathing over TRT were studied. Infants were grouped according to postnatal age: less than 5, greater than or equal to 5 to less than or equal to 13, and greater than 13 to less than or equal to 26 weeks. In each age group results were compared as follows: C vs. SS, C vs. NM, and SS vs. NM for each parameter studied. Before 5 weeks and after 13 weeks there was no significant difference between C and SS, C and NM, and SS and NM in DPSG and NPSG for all categories of central, mixed and obstructive apnea as well as the percentage of periodic breathing in different sleep states and over TRT. Similar results were obtained in CPG for all categories of central apnea and percentage of periodic breathing over TRT.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1986

Energy supplementation and productivity of Guatemalan sugar-cane cutters: a longitudinal approach.

A long-term energy supplementation program was carried out to determine its effect on the productivity of agricultural workers in Guatemala. The program provided, free of charge, a low-energy (24 Kcal) and a high-energy (350 Kcal) bottled, orange-flavored soft drink to two groups of long-term resident sugar-cane cutters who worked on the same plantation, located in the Pacific Coast. Previous to, and periodically thereafter during implementation of the program, data relative to energy intake and anthropometry were collected. Through data obtained from payroll lists, a longitudinal series of average productivity (tons of sugar cane cut and loaded per day) covering 48 weeks of pre-supplementation, 90 weeks of supplementation and 21 weeks post-supplementation, was constructed. Control of the supplement consumption was daily observed. Random assignment of workers to the high-energy supplement (HES) and the low-energy (LES) groups, was not possible. Prior to supplementation both groups presented the same characteristics in terms of age, energy intake level, weight, height, tricipital adiposity and daily productivity. Little variation was found throughout the time the supplement was consumed by the HES Group. Energy intake of workers increased significantly in absolute terms in relation to the LES Group, except towards the end of the 28 months' supplementation period. Energy balance was maintained by workers throughout the study period. A time series of the difference in mean productivity of the two supplement groups (Yt) was modeled using the ARIMA techniques. No auto-regressive term was present in the Yt series. The ARIMA (0,0,1) model was fitted and expanded with different intervention components. None of the estimated parameters of the intervention components were statistically significant. It was therefore concluded that no abrupt, or gradual and sustained energy supplementation effect on productivity was present.

Adolescent↗
PubMed1984

A critical comparison of the history of sudden-death infants and infants hospitalised for near-miss for SIDS.

To determine whether significant historical differences distinguish the near-miss for Sudden Infant Death from the infants who died of SIDS, we analysed the histories and clinical data from two groups of infants seen in our University Hospital and from collaborative research group. The data were obtained with the use of a standardised questionnaire and consultation of all available medical data. Sixty-five infants were identified as near-miss for SIDS after they had suffered a severe cardiorespiratory incident during sleep for which no cause could be found despite a complete medical examination. After an autopsy had failed to reveal a cause for the unexpected death 95 cases of SIDS were retained in the study. A series of 353 variables were collected from the parents, the gynaecologists, neonatologists and attending physicians. After statistical analysis, only 15 of the 353 items studied significantly differentiated between the two groups. A step-wise discriminant analysis performed on these items led to the identification of six independent variables: the time of the incident; the circumstances leading to the observation of the child; the child's sleep position; previous minor intestinal problems; the size of the family and the mother's coffee consumption. Most variables indicate that the near-miss infants were discovered and rescued earlier than the infants who died. No other historical information appeared significantly to differentiate between the two groups of infants. These data need confirmation from a prospective epidemiological survey.

Family Characteristics↗