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Biomedical subjects

A Sanchez

Publications and source records attributed to A Sanchez.

At least 73 records · Page 4Linked to original sources
PubMed2000

ch-TOGp is required for microtubule aster formation in a mammalian mitotic extract.

Microtubules induced to polymerize with taxol in a mammalian mitotic extract organize into aster-like arrays in a centrosome-independent process that is driven by microtubule motors and structural proteins. These microtubule asters accurately reflect the noncentrosomal aspects of mitotic spindle pole formation. We show here that colonic-hepatic tumor-overexpressed gene (ch-TOGp) is an abundant component of these asters. We have prepared ch-TOGp-specific antibodies and show by immunodepletion that ch-TOGp is required for microtubule aster assembly. Microtubule polymerization is severely inhibited in the absence of ch-TOGp, and silver stain analysis of the ch-TOGp immunoprecipitate indicates that it is not present in a preformed complex and is the only protein removed from the extract during immunodepletion. Furthermore, the reduction in microtubule polymerization efficiency in the absence of ch-TOGp is dependent on ATP. These results demonstrate that ch-TOGp is a major constituent of microtubule asters assembled in a mammalian mitotic extract and that it is required for robust microtubule polymerization in an ATP-dependent manner in this system even though taxol is present. These data, coupled with biochemical and genetic data derived from analysis of ch-TOGp-related proteins in other organisms, indicate that ch-TOGp is a key factor regulating microtubule dynamics during mitosis.

Amino Acid Sequence↗
PubMed2000

Anomalous resonance phenomena of solitary waves with internal modes

We investigate the nonparametric, pure ac driven dynamics of nonlinear Klein-Gordon solitary waves having an internal mode of frequency Omega(i). We show that the strongest resonance arises when the driving frequency delta = Omega(i)/2, whereas when delta = Omega(i) the resonance is weaker, disappearing for nonzero damping. At resonance, the dynamics of the kink center of mass becomes chaotic. As we identify the resonance mechanism as an indirect coupling to the internal mode due to its symmetry, we expect similar results for other systems.

Journal Article↗
PubMed2000

Effectiveness of four hours of education in interpretation of radiographic studies.

Clinicians working with oropharyngeal swallowing disorders often use videofluoroscopy to define their patients' swallowing abnormalities. This study examined the effect of 4 hours of training in the identification of head and neck anatomy and oropharyngeal swallowing disorders viewed radiographically. Ninety clinicians participated in a 5-hour session which included 30-minute pre- and post-tests requiring identification of head and neck anatomy and oropharyngeal swallowing disorders and a 4-hour training period. Results showed significant improvement in identification of both radiographic anatomy and swallowing disorders. The change in pre- and post-test measures was negatively correlated with extent of prior experience in dysphagia. Similar studies are needed with clinicians or students inexperienced in dysphagia to define the number of hours of education needed in order for students to reach a desired accuracy level in their identifications.

Cineradiography↗
PubMed2000

Genetic markers of immunoglobulins and diabetes mellitus in the multiracial population of New Caledonia. The CALDIA Study Group.

GM and KM immunoglobulin allotypes, which are the markers, respectively, of the constant parts of the heavy and the light chains of the IgG1, IgG2 and IgG3 subclasses, have been analysed in diabetic mellitus patients and controls living in New Caledonia. We tested 40 Europeans, 256 Melanesians and 44 Polynesians, as well as their 340 matched controls, in order to search for a genetic susceptibility at those polymorphic loci. All the subjects were tested for G1M (1, 2, 3, 17), G2M (23), G3M (5, 6, 10, 11, 13, 14, 15, 16, 21, 24, 28) and KM (1) by the classical hemagglutination method. The frequencies of GM haplotypes and KM alleles have been estimated by a maximum likelihood method. The results are in favour of no influence of the GM and KM loci. The prevalence of diabetes mellitus varies in the populations of New Caledonia: Polynesians are at much higher risk than Melanesians or Europeans. The GM haplotype distribution differs among ethnic groups; so they provide a useful marker to measure genetic admixture. The higher prevalence of diabetes observed among New Caledonians of European origin compared to the prevalence in Europe may be explained by genetic admixture with neighbouring Pacific populations, notably Polynesians (Asian haplotypes are present at a frequency of 9.4%). So, the genetic admixture should be measured in any genetic epidemiological study.

Adult↗
PubMed2000

Microsatellite alterations and TP53 mutations in plasma DNA of small-cell lung cancer patients: follow-up study and prognostic significance.

BACKGROUND: Small-cell lung cancer (SCLC), one of the major types of lung cancer, is associated with many different somatic molecular genetic changes. These alterations, observed in tumor DNA, have also been identified in the plasma DNA of patients. We undertook the present study to make a prospective investigation into the correlation between abnormal plasma DNA and patient survival. PATIENTS AND METHODS: Thirty-five patients with SCLC were selected after histological diagnosis. Polymorphic markers (ACTBP2, UT762 and AR) were chosen for their reported high rate of alterations in SCLC and analyzed in tumor tissue, normal blood cells and plasma DNA. Furthermore, we looked for mutations of the TP53 gene in tumor and plasma DNA. RESULTS: In 25 patients (71%) at least one molecular change precisely matching that of the primary tumor was detected in the plasma DNA. No difference in survival was observed between patients with aberrant plasma DNA and patients without plasma DNA alterations. However, patients with microsatellite modifications and TP53 mutations concomitantly, showed a significant difference (P = 0.02) in survival compared with patients bearing only one of these molecular changes. In 15 cases it was possible to find a correlation either between tumor response and disappearance of abnormal plasma DNA, or tumor progression and persistence of plasma DNA alterations. CONCLUSIONS: Free plasma DNA with molecular alterations is present to a high degree in plasma DNA of SCLC patients and may have a role as a prognostic factor.

Adult↗
PubMed2000

Identification of the Ebola virus glycoprotein as the main viral determinant of vascular cell cytotoxicity and injury.

Here we defined the main viral determinant of Ebola virus pathogenicity; synthesis of the virion glycoprotein (GP) of Ebola virus Zaire induced cytotoxic effects in human endothelial cells in vitro and in vivo. This effect mapped to a serine-threonine-rich, mucin-like domain of this type I transmembrane glycoprotein, one of seven gene products of the virus. Gene transfer of GP into explanted human or porcine blood vessels caused massive endothelial cell loss within 48 hours that led to a substantial increase in vascular permeability. Deletion of the mucin-like region of GP abolished these effects without affecting protein expression or function. GP derived from the Reston strain of virus, which causes disease in nonhuman primates but not in man, did not disrupt the vasculature of human blood vessels. In contrast, the Zaire GP induced endothelial cell disruption and cytotoxicity in both nonhuman primate and human blood vessels, and the mucin domain was required for this effect. These findings indicate that GP, through its mucin domain, is the viral determinant of Ebola pathogenicity and likely contributes to hemorrhage during infection.

Animals↗
PubMed2000

Multiparticle biased diffusion-limited aggregation with surface diffusion: A comprehensive model of electrodeposition

We present a complete study of the multiparticle biased diffusion-limited aggregation (MBDLA) model supplemented with surface diffusion (SD), focusing on the relevance and effects of the latter transport mechanism. By comparing different algorithms, we show that MBDLA + SD is a very good qualitative model for electrodeposition in essentially the whole range of current intensities provided one introduces SD in the model in the proper fashion. We have found that the correct procedure involves simultaneous bulk diffusion and SD, introducing a time scale arising from the ratio of the rates of the two processes. We discuss in detail the different morphologies obtained and compare them to the available experimental data with very satisfactory results. We also characterize the aggregates thus obtained by means of the dynamic scaling exponents of the interface height, allowing us to distinguish several regimes in the mentioned interface growth. Our asymptotic scaling exponents are again in good agreement with recent experiments. We conclude by discussing a global picture of the influence and consequences of SD in electrodeposition.

Journal Article↗
PubMed2000

Roughening and super-roughening in the ordered and random two-dimensional sine-gordon models

We present a comparative numerical study of the ordered and the random two-dimensional sine-Gordon models on a lattice. We analytically compute the main features of the expected high-temperature phase of both models, described by the Edwards-Wilkinson equation. We then use those results to locate the transition temperatures of both models in our Langevin dynamics simulations. We show that our results reconcile previous contradictory numerical works concerning the super-roughening transition in the random sine-Gordon model. We also find evidence supporting the existence of two different low-temperature phases for the disordered model. We discuss our results in view of the different analytical predictions available and comment on the nature of these two putative phases.

Journal Article↗
PubMed2000

Resonances in the dynamics of straight phi(4) kinks perturbed by ac forces

We study the dynamics of straight phi(4) kinks perturbed by an ac force, both with and without damping. We address this issue by using a collective coordinate theory, which allows us to reduce the problem to the dynamics of the kink center and width. We carry out a careful analysis of the corresponding ordinary differential equations, of Mathieu type in the undamped case, finding and characterizing the resonant frequencies and the regions of existence of resonant solutions. We verify the accuracy of our predictions by numerical simulation of the full partial differential equation, showing that the collective coordinate prediction is very accurate. Numerical simulations for the damped case establish that the strongest resonance is the one at half the frequency of the internal mode of the kink. In conclusion, we discuss the possible relevance of our results for other systems, especially the sine-Gordon equation. We also obtain additional results regarding the equivalence between different collective coordinate methods applied to this problem.

Journal Article↗
PubMed2000

Existence of internal modes of sine-gordon kinks

We study whether or not sine-Gordon kinks exhibit internal modes or "quasimodes." By considering the response of the kinks to ac forces and initial distortions, we show that neither intrinsic internal modes nor "quasimodes" exist in contrast to previous reports. However, we do identify a different kind of internal mode bifurcating from the bottom edge of the phonon band which arises from the discretization of the system in the numerical simulations, thus confirming recent predictions.

Journal Article↗
PubMed2000

Dichlorobis(3,5-dimethylpyrazole-N2)methylphenyltin(IV)

The title compound, [SnCl(2)(CH(3))(C(6)H(5))(C(5)H(8)N(2))(2)], was obtained by reaction of dichloromethylphenyltin(IV) and 3, 5-dimethylpyrazole (dmpz) in chloroform, and was recrystallized from acetone. The structure consists of octahedral all-trans [SnMePhCl(2)(dmpz)(2)] molecules, with the Sn atom coordinated to two C [Sn-C 2.127 (5) and 2.135 (4) A], two Cl [Sn-Cl 2.5753 (8) A] and two N atoms [Sn-N 2.357 (3) A]. The dmpz ligands, bound to the metal through their unprotonated N atoms, form weak intra- and intermolecular hydrogen bonds with the Cl ligands via their NH groups, giving rise to a polymeric chain along the c axis.

Journal Article↗
PubMed2000

Weak and strong hydrogen-bonding patterns in the structure of 2, 4-bis(2-hydroxybenzoyl)-2,3-dihydro-1H-pyrido

The title compound, C(25)H(19)NO(4)S, (IV), was produced by a cyclocondensation reaction similar to that which had previously produced an unexpected product, thus giving a novel route for such reactions. The structure of (IV) contains two S(6) motifs formed by strong intramolecular O-H.O hydrogen bonds. Weak C-H.O hydrogen bonds form primary C(11), R(1)(2)(7) and R(2)(2)(8) motifs which combine to form a complex three-dimensional network.

Journal Article↗
PubMed2000

Postoperative febrile morbidity in the benign gynecologic patient. Identification and management.

OBJECTIVE: To identify a useful temperature threshold and occurrence frequency that might represent genuine morbidity and to identify elements of the fever evaluation that were most useful in discriminating ill patients from those with transient and inconsequential temperature elevations. STUDY DESIGN: A retrospective chart review of postoperative gynecologic patients was undertaken for a one-year period. Data regarding temperatures, frequencies and workup were collected, as were descriptive data regarding the patient and case. RESULTS: Some of the previously reported associations, such as menopausal status and insurance coverage, failed to materialize as associated with temperature increases in this study. Other associations, such as blood loss and length of surgery, were confirmed. The commonly used threshold for "fever" of 38 degrees C was not as discriminatory as a threshold of 38.3 degrees C. Frequency, as well as absolute degree of elevation, did appear to relate to level of morbidity. The most useful studies in assessing temperature elevations were the white blood cell count and chest radiography. CONCLUSION: Although prospective evaluation is difficult and much work remains to be done, our data are sufficiently compelling to suggest a minimum temperature and frequency at which the otherwise-well-appearing postoperative patient should be assessed for infection. We also found the yield sufficient to make routine ordering useful only in the case of the white blood cell count and possibly the chest radiograph. Other tests should be reserved for use if directed by the physical examination or patient history.

Adult↗