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Biomedical subjects

R Jimenez

Publications and source records attributed to R Jimenez.

At least 19 recordsLinked to original sources
PubMed2006

Salt and solvent effects on the kinetics and thermodynamics of the inclusion of the ruthenium complex [Ru(NH3)5(4,4'-bpy)]2+ in beta-cyclodextrin.

The influences of solvents (in water-cosolvent mixtures) and salts on the kinetics and thermodynamics of the inclusion of [Ru(NH3)5(4,4'-bpy)]2+ in beta-cyclodextrin (beta-CD) have been studied. Solvent effects on the kinetics can be described as a consequence of the competition of the cosolvent for the beta-CD cavity. The salt effects on the kinetics depend on the ion pairing of the anions with the [Ru(NH3)5(4,4'-bpy)]2+ complex. On the other hand, the solvent effects on the equilibrium constant depend on the stabilization of the 4,4'-bipyridine ligand in the water-cosolvent mixture relative to water. Finally, salt effects on the equilibrium constant are interpreted as a consequence of ion pairing between the anion of the salt and the inclusion complex.

Kinetics↗
PubMed2005

Strength and character of peptide/anion interactions.

The binding free energy of complex [Co(C(2)O(4))(3)](3-) to three peptides H-Lys-Gly-Lys-Gly-Lys-Gly-Lys-NH(2) (P-1), H-(Lys-Gly-Lys-Gly-Lys-Gly-Lys)(2)-NH(2) (P-2), H-(Lys-Gly-Lys-Gly-Lys-Gly-Lys)(3)-NH(2) (P-3) and to the monomers (amino acids) forming the peptides has been obtained using the kinetics of the electron-transfer reaction between [Ru(NH(3))(5)py](2+) and [Co(C(2)O(4))(3)](3-) as the probe. The polymerization of the monomers increases the negative free energy of binding and changes its character, noncooperative for the monomers and anticooperative for the peptides. This increase in the negative free energy represents a driving force for the polymerization process. The magnitude of the gain in negative free energy, as a consequence of the anticooperative character of the binding of the cobalt complex to the peptide, depends on the ratio of [complex]/[monomers].

Amino Acids↗
PubMed2001

How not to be seen: the contribution of similarity and selective ignoring to sustained inattentional blindness.

When people attend to objects or events in a visual display, they often fail to notice an additional, unexpected, but fully visible object or event in the same display. This phenomenon is now known as inattentional blindness. We present a new approach to the study of sustained inattentional blindness for dynamic events in order to explore the roles of similarity, distinctiveness, and attentional set in the detection of unexpected objects. In Experiment 1, we found that the similarity of an unexpected object to other objects in the display influences attentional capture: The more similar an unexpected object is to the attended items, and the greater its differencefrom the ignored items, the more likely it is that people will notice it. Experiment 2 explored whether this effect of similarity is driven by selective ignoring of irrelevant items or by selective focusing on attended items. The results of Experiment 3 suggest that the distinctiveness of the unexpected object alone cannot entirely account for the similarity effects found in the first two experiments; when attending to black items or white items in a dynamic display, nearly 30% of observers failed to notice a bright red cross move across the display, even though it had a unique color, luminance, shape, and motion trajectory and was visible for 5s. Together, the results suggest that inattentional blindness for ongoing dynamic events depends both on the similarity of the unexpected object to the other objects in the display and on the observer's attentional set.

Adult↗
PubMed2001

Determination of lumbar muscular activity in helicopter pilots: a new approach.

BACKGROUND: Discomfort in the lumbar region is a frequent complaint of helicopter pilots. Two factors that helicopter crewmembers relate to back pain are exposure to vibration and poor posture during flight, because during flight the seat and controls force the pilot to adopt an asymmetric posture. Repeated exposure to these adverse flight conditions could cause pathological changes in the spine. The purpose of this study was to compare right and left sided lumbar muscular activity in helicopter pilots under real flight conditions, using surface electromyography (SEMG) to demonstrate the effects of asymmetrical posture on the musculoskeletal system. An attempt was also made to correlate lumbar muscular activity with environmental factors and such variables as type of flight, type of helicopter, duration of flight, age, physical fitness, and height. METHODS: Right- and left-sided lumbar electrical activity were measured using two-channel SEMG during 35 flights in 2 types of helicopter and a cockpit mock-up. RESULTS: There was a statistically significant increase in right-sided lumbar activity when related to the duration of flight. CONCLUSIONS: The data showed that when the pilot used the manual controls during flight, he did not maintain a symmetrical posture and contracted one side more than the other. We think the relationship between the greatest right-sided contraction and flight duration is due to maintaining an asymmetric posture over a long period. We also noted a tendency towards greater right lumbar musculature activity in older pilots.

Adult↗
PubMed2000

Periodic occurrence of epithelial viral necrosis outbreaks in Penaeus vannamei in Ecuador.

Epizootics of an infectious cuticular epithelial necrosis virus (ICENV) occurred in cultured Penaeus vannamei in Ecuadorian shrimp farms from 1994 to 1996. There were few reports of outbreaks during 1997, but in the second half of 1998 epizootics were again reported. Histopathological examination revealed extensive tissue changes and necrosis as described for infections by what others have called Taura syndrome virus (TSV). Infiltration of haemocytes in the cuticular epithelium was also one of the characteristics in the subacute and acute forms of this disease. Electron microscopy of affected tissues demonstrated the presence of a single type of virus particle in the cytoplasm of diseased shrimps from these outbreaks and it corresponded to the published descriptions for TSV. The epizootics of ICENV were periodic in occurrence, and data indicated that they might be related to the oceanographic and climatic variations reported in the eastern Pacific from 1994 to 1998. Using 3 mo rolling averages, a statistically significant negative correlation was found between prevalence of ICENV and temperature but not temperature change. By contrast, there was a statistically significant positive correlation between prevalence of ICENV and salinity change but not salinity value. Although these data do not establish causal relationships, they suggest that laboratory tests should be conducted to determine whether low temperature and upward changes in salinity can increase shrimp susceptibility to infection and mortality by ICENV.

Animals↗
PubMed2000

Expression of glucokinase in skeletal muscle: a new approach to counteract diabetic hyperglycemia.

Chronic hyperglycemia is responsible for diabetes-specific microvascular and macrovascular complications. To reduce hyperglycemia, key tissues may be engineered to take up glucose. To determine whether an increase in skeletal muscle glucose phosphorylation leads to increased glucose uptake and to normalization of diabetic alterations, the liver enzyme glucokinase (GK) was expressed in muscle of transgenic mice. GK has a high Km for glucose and its activity is not inhibited by glucose 6-phosphate. The presence of GK activity in skeletal muscle resulted in increased concentrations of glucose 6-phosphate and glycogen. These mice showed lower glycemia and insulinemia, increased serum lactate levels, and higher blood glucose disposal after an intraperitoneal glucose tolerance test. Furthermore, transgenic mice were more sensitive to injection of low doses of insulin, which led to increased blood glucose disposal. In addition, streptozotocin (STZ)-treated transgenic mice showed lower levels of blood glucose than STZ-treated controls and maintained body weight. Moreover, injection of insulin to STZ-treated transgenic mice led to normoglycemia, while STZ-treated control mice remained highly hyperglycemic. Thus, these results are consistent with a key role of glucose phosphorylation in regulating glucose metabolism in skeletal muscle. Furthermore, this study suggests that engineering skeletal muscle to express GK may be a new approach to the therapy of diabetes mellitus.

Animals↗
PubMed1999

Preproenkephalin mRNA and enkephalin levels in the adult Syrian hamster: the influence from glucocorticoids.

Proenkephalin (Penk) gene structure in hamsters and humans are similar but they differ from rats. In this study hamster Penk gene expression was examined after hypophysectomy+/-glucocorticoid receptor blockade with RU 486 (mifepristone). In contrast to rats, basal Penk gene expression in hamster adrenals did not change after treatments that reduced both the influence from glucocorticoids and phenylethanolamine-N-methyltransferase mRNA levels. Meanwhile, striatal preproenkephalin mRNA levels increased under these conditions.

Adrenal Glands↗
PubMed1998

Aetiology of ovine footrot in Spain.

Four hundred and sixty strains of obligate anaerobes were isolated from 216 cases of ovine foot rot distributed throughout Spain. The predominant species was Dichelobacter nodosus, which was isolated in 168 cases (77.8 per cent). A higher proportion of the strains of D nodosus than of the other strains had elastolytic activity, 118 of the 168 strains degrading elastin. Species belonging to the genus Prevotella were isolated from 96 cases (44.4 per cent). Serotyping of the D nodosus strains showed that serovars A1, A2 and C were the most commonly isolated in Spain.

Animals↗
PubMed1998

Globular cluster ages.

We review two new methods to determine the age of globular clusters (GCs). These two methods are more accurate than the classical isochrone fitting technique. The first method is based on the morphology of the horizontal branch and is independent of the distance modulus of the globular cluster. The second method uses a careful binning of the stellar luminosity function and determines simultaneously the distance and age of the GC. We find that the oldest galactic GCs have an age of 13.5 +/- 2 gigayears (Gyr). The absolute minimum age for the oldest GCs is 10.5 Gyr (with 99% confidence) and the maximum 16.0 Gyr (with 99% confidence). Therefore, an Einstein-De Sitter Universe (Omega = 1) is not totally ruled out if the Hubble constant is about 65 +/- 10 Km s-1 Mpc-1.

Journal Article↗
PubMed1998

HIV/AIDS practice patterns, knowledge, and educational needs among Hispanic clinicians in Texas, USA, and Nuevo Leon, Mexico.

Hispanic clinicians in Texas, United States of America, and in the neighboring state of Nuevo Leon, Mexico, were surveyed to determine their educational needs in the area of HIV/AIDS. Two-thirds of the 74 Texan and 22% of the 104 Mexican physicians queried had seen at least one HIV/AIDS patient in the previous year. The majority of the respondents were primary care physicians who: 1) were in private practice; 2) saw more than 1,000 patients per year; 3) had been out of training for more than 10 years; 4) provided some HIV prevention education to patients based on their perceived risk of infection; 5) rated their own knowledge of HIV/AIDS as average but rated their knowledge of treatments for the disease below average; 6) received most of their information about HIV/AIDS from journals rather than formal continuing education programs; 7) thought Hispanic patients had special needs with regard to HIV/AIDS care; and 8) were willing to attend education programs to improve their HIV/AIDS management skills. The greatest barriers to caring for HIV patients were lack of clinical knowledge and fear of infection. These results point to a need for a large-scale training program to improve the HIV/AIDS management skills of Hispanic clinicians in Texas and Nuevo Leon.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Body cavity-based malignant lymphoma containing Kaposi sarcoma-associated herpesvirus in an HIV-negative man with previous Kaposi sarcoma.

BACKGROUND: The role of Kaposi sarcoma-associated herpesvirus in the development of malignant lymphomas in patients negative for the human immunodeficiency virus (HIV) has not been established. OBJECTIVE: To examine the possible role of Kaposi sarcoma-associated herpesvirus in a case of body cavity-based malignant lymphoma that occurred in an HIV-negative patient who had previously had Kaposi sarcoma. DESIGN: Case study. SETTING: Academic medical center. PATIENT: A 94-year-old man with lymphomatous ascites. MEASUREMENTS: Polymerase chain reaction (PCR) and Southern blot DNA analysis. RESULTS: The body cavity-based lymphoma cells were positive for Kaposi sarcoma-associated herpesvirus by PCR and were negative for other herpesviruses, including Epstein-Barr virus, cytomegalovirus, and human herpesviruses 6 and 7. Southern blot analysis of lymphoma DNA showed high levels of Kaposi sarcoma-associated herpesvirus (> 40 to 80 genomes/cell). Clonal rearrangement of the immunoglobulin JH and JK genes was present, confirming the presence of a clonal B-cell proliferation. CONCLUSIONS: Kaposi sarcoma-associated herpesvirus may be involved in the development of malignant lymphoma after Kaposi sarcoma in HIV-negative patients. This type of lymphoma, in contrast to body cavity-based lymphoma related to the acquired immunodeficiency syndrome, may have an indolent clinical course.

Aged↗
PubMed1995

Inhibition of neutrophil adhesion by adenosine and an adenosine kinase inhibitor. The role of selectins.

Adenosine and adenosine analogues exhibit anti-inflammatory effects in vitro and in vivo, but their usefulness is limited by profound cardiovascular side effects. Therefore, we synthesized inhibitors of an enzyme involved in adenosine metabolism, adenosine kinase (AK) (EC 2.7.1.20), to enhance endogenous adenosine concentrations at sites of inflammation. GP-1-515 (4-amino-1-(5-amino-5-deoxy-1-beta-D- ribofuranosyl)-3-bromo-pyrazolo[3,4-d]pyrimidine), a novel AK inhibitor, decreased adhesion of activated human neutrophils to cultured endothelial cell monolayers by increasing local adenosine levels. The mechanism of inhibition in this assay seemed to involve selectin blockade and was independent of the beta 2 integrins. GP-1-515 and 2-chloroadenosine (a nonmetabolizable adenosine analogue) had no effect on the surface expression or shedding of adhesion molecules. An agent that disrupts the cytoskeleton, cytochalasin B, mimicked the effect of adenosine on cell adhesion. Interactions between L-selectin and the neutrophil cytoskeleton might be altered by adenosine and could contribute to adenosine-mediated adhesion inhibition.

2-Chloroadenosine↗
PubMed1995

Influence of vitamin C on the absorption and first pass metabolism of propranolol.

The effect of ascorbic acid on the availability of propranolol has been examined. After oral administration of propranolol 80 mg with or without ascorbic acid pretreatment (2 g), the plasma concentrations and urinary excretion of propranolol and its metabolites, 4-hydroxy-propranolol and propranolol-conjugated, were determined by HPLC. Compared to controls, vitamin C decreased the maximum concentration of propranolol from 463 to 334 nmol.l-1, and the area under the propranolol concentration-time curve (from 0 to 24 hours) from 3.13 to 1.96 mumol.l-1.h. The time to reach maximum propranolol concentration was increased from 1.9 to 2.7. The total amount of drug recovered in urine has also significantly diminished (from 12.6 to 4.29 mg). No change in elimination rate was observed, indicating that ascorbic acid had affected both the absorption process and the first pass metabolism. The heart-rate decreased less when propranolol was administered with ascorbic acid in comparison to control subjects, although this interaction has little biological importance.

Administration, Oral↗
PubMed1995

X-linked familial exudative vitreoretinopathy. Report of one family.

BACKGROUND: Familial exudative vitreoretinopathy is an uncommon heredodegenerative disease with different types of inheritance and degrees of severity. METHODS: Findings in five affected members of a family in which the X-linked mode of inheritance of familial exudative vitreoretinopathy is present are discussed. RESULTS: Patients presented with characteristic retinal exudative tractional detachment, temporal retinal vessel traction, capillary dilatation, neovascularization, and vitreous veils. CONCLUSION: A review of the 21 cases of X-linked familial exudative vitreoretinopathy reported to date indicates a worse outcome in this mode of inheritance than in cases of autosomal dominant inheritance.

Adolescent↗