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Biomedical subjects

O Hernandez

Publications and source records attributed to O Hernandez.

At least 19 recordsLinked to original sources
PubMed2003

Synthesis, crystal structure, and characterization of the first Nb(3) triangular cluster compound bonded to fluorine ligands: association of Nb(3)I(i)F(i)(3)F(a)(8)L(a) units and Nb(IV)L(6) Octahedra with L=O and F.

The synthesis and the crystal structure of the first compound containing Nb(3) triangular clusters bonded to fluorine ligands are presented in this work. The structure of Nb(3)IF(7)L(NbL(2))(0.25) with L = O and F, determined by single-crystal X-ray diffraction, is based on a Nb(3)I(i)F(i)(3)F(a)(8)L(a) unit and a NbL(6) octahedron (tetragonal, space group I4/m, a = 13.8638(3) A, c = 8.9183(2) A, V = 1714.14(7) A(3), Z = 8). Two crystallographic positions (noted L5 and L6) are randomly occupied by fluorine and oxygen with two different F:O occupancies. These L ligands build an octahedral site for a single niobium atom, located between the units. The four L5 ligands of the NbL(6) octahedron are shared with four Nb(3) cluster units, while the two other L6 ligands are terminal. The Nb(3) cluster is face-capped by one iodine and edge-bridged by three fluorine ligands. Two of the three niobium atoms constituting the cluster are bonded to three additional apical fluorine ligands, while the third one is bonded to two fluorines and one L5 ligand. The Nb(3) cluster is linked to six adjacent ones via all the apical fluorine ligands. The developed formula of the unit is therefore Nb(3)I(i)F(i)(3)F(a)(-)(a)(8/2)L(a) according to the Schäfer and Schnering notation. The oxidation state of the single niobium and the random distribution of fluorine and oxygen on the two L sites will be discussed on the basis of structural analysis, the bond valence method, and IR and EPR measurements. The structural results will be compared to those of previously reported niobium compounds containing NbF(6) or Nb(F,O)(6) octahedra.

Journal Article↗
PubMed2001

1,3,5-Triiodo-2,4,6-trimethylbenzene at 293 K.

In the structure of triiodomesitylene (1,3,5-triiodo-2,4,6-trimethylbenzene), C(9)H(9)I(3), at 293 K, the benzene ring is found to be significantly distorted from ideal D(6h) symmetry; the average endocyclic angles facing the I atoms and the methyl groups are 123.8 (3) and 116.2 (3) degrees, respectively. The angle between the normal to the molecular plane and the normal to the (100) plane is 5.1 degrees. No disorder was detected at 293 K. The thermal motion was investigated by a rigid-body motion tensor analysis. Intra- and intermolecular contacts are described and topological differences compared with the isomorphous compounds trichloromesitylene and tribromomesitylene are discussed.

Journal Article↗
PubMed2001

Structure of the X-phase of 38% brominated betaine calcium chloride dihydrate.

The structures of the high- and low-temperature phases of 38% brominated BCCD [betaine (trimethylammonioacetate) calcium chloride dihydrate], the latter being known as the X-phase, have been determined by single-crystal neutron diffraction at 295 and 20 K, respectively. The symmetry of the X-phase is described by the P2(1)2(1)2(1) space group. The distortion with respect to the high-temperature Pnma phase is characterized by anti-symmetric displacements of the betaine molecules as well as of the Ca octahedra. On the basis of a symmetry-mode analysis, we propose an interpretation of the direct phase transition that occurs around 80 K between these two phases.

Journal Article↗
PubMed2000

An evaluation of the impact of training Honduran health care providers in interpersonal communication.

OBJECTIVE: To evaluate the impact of interpersonal communication (IPC) training on practice and patient satisfaction and to determine the acceptability of this training to providers in a developing country. DESIGN: The study used a pre-post design with treatment and control groups. Data collection methods included interaction analysis of audio-taped clinical encounters, patient exit interviews, and a self-administered questionnaire for health providers. STUDY PARTICIPANTS: Interaction analysis was based on an experimental group of 24 doctors and a control group of eight with multiple observations for each provider). Exit interviews were carried out with 220 pre-test patients and 218 post-test patients. All 87 health providers who received training responded to the self-administered questionnaire. INTERVENTION: A brief in-service training programme on interpersonal communications was presented in three half-day sessions; these focused on overall socio-emotional communication, problem solving skills and counselling. MAIN OUTCOME MEASURES AND RESULTS: The IPC intervention was associated with more communication by trained providers (mean scores of 136.6 versus 94.4; P = 0.001), more positive talk (15.93 versus 7.99; P = 0.001), less negative talk (0.11 versus 0.59; P = 0.018), more emotional talk (15.7 versus 5.5; P = 0.021), and more medical counselling (17.3 versus 11.3; P = 0.026). Patients responded by communicating more (mean scores of 113.8 versus 79.6; P = 0.011) and disclosing more medical information (54.7 versus 41.7; P = 0.002). Patient satisfaction ratings were higher for providers who had received the training and providers reported training to be relevant and useful. CONCLUSIONS: Further validation of IPC skills and simplification of assessment methods are needed if IPC is to be an area for routine monitoring and quality improvement.

Ambulatory Care↗
PubMed1999

Hypoxia-activated apoptosis of cardiac myocytes requires reoxygenation or a pH shift and is independent of p53.

Ischemia and reperfusion activate cardiac myocyte apoptosis, which may be an important feature in the progression of ischemic heart disease. The relative contributions of ischemia and reperfusion to apoptotic signal transduction have not been established. We report here that severe chronic hypoxia alone does not cause apoptosis of cardiac myocytes in culture. When rapidly contracting cardiac myocytes were exposed to chronic hypoxia, apoptosis occurred only when there was a decrease in extracellular pH ([pH](o)). Apoptosis did not occur when [pH](o) was neutralized. Addition of acidic medium from hypoxic cultures or exogenous lactic acid stimulated apoptosis in aerobic myocytes. Hypoxia-acidosis-mediated cell death was independent of p53: equivalent apoptosis occurred in cardiac myocytes isolated from wild-type and p53 knockout mice, and hypoxia caused no detectable change in p53 abundance or p53-dependent transcription. Reoxygenation of hypoxic cardiac myocytes induced apoptosis in 25-30% of the cells and was also independent of p53 by the same criteria. Finally, equivalent levels of apoptosis, as demonstrated by DNA fragmentation, were induced by ischemia-reperfusion, but not by ischemia alone, of Langendorff-perfused hearts from wild-type and p53 knockout mice. We conclude that acidosis, reoxygenation, and reperfusion, but not hypoxia (or ischemia) alone, are strong stimuli for programmed cell death that is substantially independent of p53.

Acidosis, Lactic↗
PubMed1998

The effects of a continuing medical education programme in interpersonal communication skills on doctor practice and patient satisfaction in Trinidad and Tobago.

This study investigates the effects of a brief training programme on the communication skills of doctors in ambulatory care settings in Trinidad and Tobago. Evaluation of doctor performance is based on analysis of audiotapes of doctors with their patients during routine clinic visits and on patient satisfaction ratings. A pre-test/post-test quasi-experimental study design was used to evaluate the effects of exposure to the training programme. Doctors were assigned to groups based on voluntary participation in the programme. Audiotapes of the 15 participating doctors (nine trained and six control) with 75 patients at baseline and 71 patients at the post-training assessment were used in this analysis. The audiotapes were content-coded using the Roter Interaction Analysis System (RIAS). Doctors trained in communication skills used significantly more target skills post-training than their untrained colleagues. Trained doctors used more facilitations in their visits and more open-ended questions than other doctors. There was also a trend towards more emotional talk, and more close-ended questions. Patients of trained doctors talked more overall, gave more information to their doctors and tended to use more positive talk compared to other patients. Trained doctors were judged as sounding more interested and friendly, while patients of trained doctors were judged as sounding more dominant, responsive and friendly than patients of untrained doctors. Consistent with these communication differences, patient satisfaction tended to be higher in visits of trained doctors.

Adult↗
PubMed1996

Evidence of asynchrony in the onset of signs of oestrus in zebu cattle treated with a progestogen ear implant.

Thirty-two zebu cows aged three to nine years were given a progestogen implant to determine their oestrous response. The experiment was carried out in two parts: in the first, 15 cows were induced to display oestrus, one animal per day during the dry season; in the second, 17 cows were selected for daily induction during the wet season. The animals were observed continuously from 24 hours after the removal of the first implant until 48 hours after the withdrawal of the last. There were no significant differences between the durations of the pre-receptive phase (pro-oestrus), receptive phase (oestrus) and post-receptive phase (metoestrus) in the two trials. The average expression of oestrus after the withdrawal of the implant was 60 per cent in the dry season and 35.2 per cent in the wet season (P < 0.05). Furthermore, only 60 per cent of the animals responded by displaying sexual activity within the expected range of 31 to 57 hours after withdrawal of the implant. The distributions of the animals displaying sexual behaviour in the wet and the dry seasons were similar. It is suggested that zebu cows under field conditions tend to manifest synergistic sexual behaviour.

Animals↗
PubMed1995

Characterization of B27 haplotypes by oligotyping and genomic sequencing in the Mexican Mestizo population with ankylosing spondylitis: juvenile and adult onset.

The aim of this study was to investigate the contribution of the different B27 subtypes in the Mexican Mestizo population with juvenile and adult AS. No differences in the distribution of B27 subtypes were found between both populations, B*2705 being the predominant subtype followed by B*2702. Transracial gene mapping was performed in order to find out the origin of the B27 alleles of the Mexican Mestizos. A PCR with SSOPs was used to analyze the polymorphism in exons 2 and 3 of HLA-B27 and HLA-C related alleles. This population shares with the Spanish Caucasians B*2705 and B*2702, which are absent in Central and South American Indians. AS and healthy Mexican mestizo donors were analyzed to ascertain B27/Cw haplotypes. The B27/Cw linkage arrangements seen in mestizos are similar to those reported for Caucasian Spaniards with three different haplotypes positively associated with AS in both populations, B*2705/Cw*0102, B*2705/Cw*02022, and B*2702/Cw*02022, suggesting that B27 in Mexicans may be due to a recent Caucasoid admixture with the Spanish genes. Finally, a strategy for sequence analysis of exons 2 and 3 from genomic DNA of HLA-B27 alleles was developed. A novel HLA-B27-like allele typed serologically as B27 was identified and sequenced by this method in a healthy Mexican mestizo, corresponding to the B*7301 variant found with low frequency in different populations. Analysis of the association of B*7301 to AS would require an extensive study in different populations and could provide insights into the molecular structure of the alleles involved in the disease.

Adolescent↗
PubMed1993

Effects of dopaminergic antagonists on dopamine-induced cardiovascular and insulin secretion actions in hypertensive patients.

A comparative study between two dopaminergic antagonists: metoclopramide and domperidone, was undertaken in nineteen (19) hypertensive patients at the Vargas Hospital, Caracas. The patients were pretreated with labetalol, 800-1,200 mg/day, orally, over a period of one week, after which they were divided into two groups: group A, a total of eleven patients were intravenously infused with dopamine hydrochloride 0.5-3 micrograms/kg/min, before and after treatment with metoclopramide (10 mg, i.v. as a bolus); group B (n = 8), was pretreated with domperidone, 20 mg b.i.d., p.o. over a period of one week and intravenously infused with dopamine hydrochloride, 0.5-3 micrograms/kg/min. In group A, dopamine induced a decrease of blood pressure from 171.9 +/- 6.35/103.6 +/- 3.12 to 152.7 +/- 7.55/93.8 +/- 2.97 mmHg (p < 0.001) without altering heart rate, and it increased plasma insulin levels from 8.29 +/- 0.70 microunits/ml to 12.09 +/- 1.83 microunits/ml (p < 0.01). Metoclopramide caused no changes of blood pressure or plasma insulin levels. However, hypotensive responses and plasma insulin rises due to dopamine were blocked by metoclopramide. In group B, domperidone also blocked dopamine-induced antihypertensive effect (from 170.0 +/- 9.23/102.8 +/- 3.80 to 160.2 +/- 9.84/95.5 +/- 2.50 mmHg) although it was less effective than metoclopramide. Domperidone also blocked dopamine-induced increase of plasma insulin levels from 9.65 +/- 4.50 microunits/ml to 11.78 microunits/ml. We conclude that a dopaminergic receptor may be involved in some cardiovascular responses and in modulating insulin secretion in man.

Blood Glucose↗
PubMed1988

Analysis of glutathione conjugates and related compounds by thermospray mass spectrometry.

A series of 17 cysteine, N-acetyl cysteine, glutathione, and N-trifluoroacetyl glutathione conjugates have been prepared, and their thermospray (TSP) spectra have been recorded in the positive and negative ion modes. The compounds undergo extensive fragmentation, which primarily occurs at the carbon-sulfur bonds. For most of the compounds, positive ion TSP is more sensitive than negative ion thermospray. Probably due to the thermal lability of these adducts, the quality of the spectra obtained are dependent on source conditions, requiring fine control of the vaporization/desolvation process.

Chemical Phenomena↗
PubMed1987

The stereoselectivity of four hepatic glutathione S-transferases purified from a marine elasmobranch (Raja erinacea) with several K-region polycyclic arene oxide substrates.

Product analysis by HPLC demonstrated that three hepatic cytosolic glutathione S-transferases of little skate (E-2, E-3 and E-4) were highly stereoselective, if not stereospecific, for thiol reaction at the R-configured oxirane carbons of four K-region arene oxides; pyrene 4,5-oxide, (+/-)-benz[a]anthracene 5,6-oxide, (+/-)-benzo[a]pyrene 4,5-oxide and phenanthrene 9,10-oxide. A fourth transferase, E-5, exhibited no stereopreference with pyrene 4,5-oxide or phenanthrene 9,10-oxide. Immunological and electrophoretic evidence has shown that the three enzymes exhibiting stereospecificity have a common subunit which is absent from enzyme E-5. The high stereoselectivity of the three enzymes E-2, E-3, and E-4 was accompanied by effective catalysis of the reaction of GSH with these K-region epoxides; for example, the calculated turnover number for E-4 with benzo[a]pyrene 4,5-oxide was 550.

Animals↗
PubMed1986

The United States Environmental Protection Agency's guidelines for applicator exposure monitoring.

The Environmental Protection Agency (EPA)'s proposed guidelines for studies which estimate worker exposure to pesticides during application and related work activities are discussed. These guidelines are intended to aid pesticide registrants in conducting occupational exposure monitoring studies for pesticide applicators at indoor and outdoor sites. The Agency's rationale for requiring exposure to be monitored with passive dosimetry techniques or by biological monitoring is described. The practical and theoretical advantages and disadvantages of both approaches are also discussed.

Environmental Exposure↗
PubMed1986

Rabbit pulmonary cytochrome P-450 monooxygenase system: isozyme differences in the rate and stereoselectivity of styrene oxidation.

The rate and stereoselectivity of the cytochrome P-450 (P-450)-dependent oxidation of styrene to styrene 7,8-oxide (SO) were determined in rabbit pulmonary microsomes and with purified rabbit pulmonary P-450 isozymes in reconstituted monooxygenase systems. Stereoselectivity was determined by separation of the diastereomeric SO-glutathione adducts by high-performance liquid chromatography; these four compounds accounted for more than 95% of the SO formed. Pulmonary microsomes preferentially formed (R)-SO [(R)-SO/(S)-SO = 1.6] at a rate of 7.5 nmol of SO formed/min/nmol of P-450. Antibodies to NADPH-P-450 reductase (antireductase) inhibited SO formation in pulmonary microsomes by greater than 98%. In the presence of antibodies to P-450 form 2 (anti-2), pulmonary microsomes oxidized styrene to equal amounts of (R)- and (S)-SO at a rate of 4.2 nmol of SO/min/nmol of total P-450; in the presence of antibodies to P-450 form 5 (anti-5), styrene was stereoselectively oxidized to (R)-SO [(R)-SO/(S)-SO = 2.0] at a rate of 6.5 nmol of SO/min/nmol of total P-450. In reconstituted monooxygenase systems, P-450 forms 2, 5 and 6 oxidized styrene to SO at rates of 10.0, 4.7 and 4.5 nmol of SO formed/min/nmol of P-450, respectively. The relative amounts of (R)-SO and (S)-SO produced were 2.0, 1.0 and 0.9, respectively. Predicted values for rate and stereoselectivity of styrene oxidation by pulmonary microsomes, calculated from the values obtained in the reconstitution experiments and the relative concentrations of the different P-450 isozymes, agreed well with experimentally determined values.

Animals↗
PubMed1985

Beta-epidermal growth factor is the des-asparaginyl form of the polypeptide.

Reversed-phase high performance liquid chromatography of mouse epidermal growth factor (EGF) yielded two major forms, alpha- and beta-EGF, and a minor component, gamma-EGF. All three forms exhibited receptor-binding activity. Analysis of native alpha- and beta-EGF by mass spectrometry and partial Edman degradation led us to propose that alpha-EGF has a primary structure equivalent to that originally reported for EGF and that beta-EGF is the des-asparaginyl form of the polypeptide. When the purified alpha- and beta-polypeptides were cultured with human embryonic palatal mesenchymal cells stimulation of cell proliferation was observed at concentrations as low as 0.01 ng/ml with maximal stimulation occurring at about 1 ng/ml. Essentially no difference was noted in the mitogenic potency of the two forms. This suggests that the NH2-terminal region of EGF is not critical for mitogenic activity.

Amino Acid Sequence↗