PubMed Health⌕ Search

Biomedical subjects

M Marcos

Publications and source records attributed to M Marcos.

At least 19 recordsLinked to original sources
PubMed2005

NMR relaxation study of molecular dynamics in columnar and smectic phases of a PAMAM liquid-crystalline co-dendrimer.

We present the first results obtained by proton ((1)H) nuclear magnetic relaxation studies of molecular dynamics in a supermolecular liquid-crystal dendrimer exhibiting columnar rectangular and smectic-A phases. The (1)H spin-lattice relaxation time (T(1)) dispersions are interpreted using two relaxation mechanisms associated with collective motions and local molecular reorientations of the dendritic segments in the low- and high-frequency ranges, respectively. The T(1) values show a drop around 2.3 MHz that is attributed to a contribution coming from cross-relaxation between (1)H and nitrogen nuclear spins. In the high-frequency range the motions appear to be of similar nature in both mesophases and are ascribed to reorientations of dendritic segments (belonging to the core and/or to the mesogenic units) characterized by two correlation times. Notable differences in the dynamics between the columnar and layered phases are observed in the low-frequency range. Depending on the mesophase they are discussed in terms of elastic deformations of the columns and layer undulations. In this study we find that the dendritic core influences the dynamics of the mesogenic units both for local and collective motions. These results can be understood in terms of spatial constraints imposed by the dendritic architecture and by the supermolecular arrangement in the mesophases.

Journal Article↗
PubMed2005

Health-related quality of life of patients with HIV: impact of sociodemographic, clinical and psychosocial factors.

OBJECTIVES: This study aims to analyse how a wide group of clinical, social, demographic and psychological factors are related to both physical and mental quality of life in HIV + patients. DESIGN: A cross-sectional study was carried out of 320 HIV + patients in antiretroviral treatment who attended infectious diseases units in four hospitals in the region of Andalusia (Spain). METHODS: Health-Related Quality of Life was measured by the MOS-HIV. Included as independent variables were: sociodemographic variables, variables related to antiretroviral therapy, psychosocial variables like social support (Duke-UNC-11) and psychological morbidity (GHQ-28), variables related to main risk behaviours and clinical variables. RESULTS: In the multiple linear regression analysis, a better PHS quality of life was found to be associated with the absence of mental illness, social support, not being an intravenous drug user and using more than one type of non-injectable drug. A better quality of life, in mental terms, was found to be associated with fewer years as a non-intravenous drug user, having social support, absence of mental illness, not being an intravenous drug user taking only one additional pill, not having any difficulty in taking the medication, and being female. CONCLUSIONS: The study of other non-biological factors that may be related to quality of life has been limited practically to social support and the emotional state. This study highlights the importance of these factors independently from the clinical state, as well as the existence of other psychological and behavioural factors that are also related.

Activities of Daily Living↗
PubMed2001

Dendromesogens: liquid crystal organizations of poly(amidoamine) dendrimers versus starburst structures.

A new series of liquid crystalline poly(amidoamine) (PAMAM) dendrimers is described. These dendrimers are made by attaching to the 0-, 1-, 2-, 3-, and 4-generation of PAMAM-terminal promesogenic units that carry two decyloxy chains in the 3- and 4-positions of their peripheral aromatic ring. X-ray diffraction studies show that all the compounds display a hexagonal columnar mesophase. A high density of aliphatic chains imposes a curved interface with the promesogenic units that forces the molecules to adopt a radial conformation, and therefore, the columnar structure. A model for the supramolecular organization of the different generations within the columnar mesophase is proposed based on the variation of some of the structural parameters.

Journal Article↗
PubMed2001

Combining diagnosis and treatment using Asbru.

Traditionally, diagnosis and treatment have been seen as two distinct tasks. Consequently, most approaches to computer supported health care focus on one of the two - mostly on diagnosis or rather on the interpretation of measurements which is much better understood and formalized. However, in practice diagnosis and treatment overlap and influence each other in many ways. Combinations range from repeatedly going through the diagnosis-treatment loop over a period of time to permanent monitoring of the patients' health condition as it is done in intensive care units. In this paper we describe how to model these combinations using the clinical protocol-representation language Asbru. It implements treatment steps in a hierarchy of skeletal, time-oriented plans. Diagnosis can either be described in a declarative way in the conditions, under which treatment steps are taken or it can be modelled explicitly as plans of their own right. We demonstrate our approach using examples taken from the American Association of Paediatricians' guideline for the treatment of hyperbilirubinemia in the new-born.

Decision Making, Computer-Assisted↗
PubMed2000

Chemoradiotherapy for muscle invading bladder carcinoma. Final report of a single institutional organ-sparing program.

PURPOSE: Chemoradiotherapy is becoming an alternative to radical cystectomy among patients with muscle invading bladder cancer. We began a prospective study in 1988 to determine the possibilities of conservative treatment and aiming to improve the results obtained by cystectomy alone in invasive bladder cancer. A combination of methotrexate, vinblastine, adriamycin, and cisplatin (M-VAC), followed by radiotherapy and concomitant cisplatin was used. METHODS: Fifty patients with good performance status and with stages T2 to T4 operable untreated invasive bladder cancer were entered in the study. Treatment protocol was as follows: (i) cytoreductive transurethral resection; (ii) two cycles of M-VAC chemotherapy; (iii) radiotherapy, 45 Gy on pelvic volume and, at the same time, 20 mg/m(2) cisplatin on days 1 to 5. Cystoscopic evaluation: if there was a complete response, radiotherapy was completed up to 65 Gy; if there was not a complete response, a cystectomy was performed. Median follow-up of the series was 73 months (18-180 m). RESULTS: Tumor response was as follows: 34 complete responses (68%), 9 partial responses (18%), and 7 nonresponses (14%) were observed. The 5-year overall survival and local control were 48% and 47%, respectively. For the complete responder patient, 5-year survival and local control were 65% and 70%, respectively. Severe toxicity was uncommon. The most frequent were leucopenia and cystitis. No treatment-related deaths occurred with either treatment protocol. CONCLUSIONS: Conservative combination treatment may be an acceptable alternative to immediate cystectomy in selected patients with bladder cancer, although a randomized clinical trial would be required to produce definitive results.

Aged↗
PubMed2000

Accidental removal of endotracheal and nasogastric tubes and intravascular catheters.

OBJECTIVES: To characterize the rates of accidental removal of endotracheal tubes, nasogastric tubes, central venous catheters, and arterial catheters. To assess the efficacy of corrective measures aimed at reducing the accidental removal of these devices. DESIGN: Prospective, observational, and interventional study. SETTING: Eighteen-bed medical-surgical intensive care unit of a 650-bed tertiary care hospital. PATIENTS: Patients admitted to the intensive care unit who had any of the following devices in place for more than 24 hrs: endotracheal tube, nasogastric tube, central venous catheter, arterial catheter. MEASUREMENTS AND INTERVENTIONS: Data were collected on the date of placement of tubes and catheters, position of vascular catheters, date of removal, and reason for removal. The study involved three consecutive 6-month periods. At the end of the first and the second periods, information about rates of accidental removal was provided to the physicians and nurses. In addition, the personnel were instructed to be more vigilant and specific measures aimed at reducing the accidental removal were introduced. MAIN RESULTS: In the first period, 289 endotracheal tubes were placed and 13.1% (24.7 per 1000 days) were removed accidentally. In the second and third periods, 17.1% (25.5 per 1000 days) and 11.4% (15.1 per 1000 days) were removed accidentally, respectively. In the first period, 368 nasogastric tubes were placed and 41% (73.9 per 1000 days) were removed accidentally. In both the second and the third period, a significant reduction in the rate of accidental removal was observed (32.4% or 41.2 per 1000 days and 25.8% or 29.8 per 1000 days, respectively). A significant decrease was observed in the rates of accidental removal of central venous catheters from 7.5% (12.4 per 1000 days) in the first period to 3.6% (5.4 per 1000 days) in the second period. The rate of arterial catheters accidentally removed expressed according to the time at risk significantly decreased from 46.5 per 1000 days in the first period to 19.1 per 1000 days in the second period and 25.3 per 1000 days in the third period. CONCLUSIONS: The information provided by the rates of accidental removal expressed by patient-days is helpful to compare results obtained in populations with different times of follow-up. Education of medical personnel and limiting upper-extremity access to within 20 cm from any catheter or tube resulted in a significant reduction of patient-related removal of tubes and catheters.

Catheterization, Central Venous↗
PubMed1995

[The dorsal flap in laboratory animals].

A total of 108 flaps were fashioned in the dorsal area of laboratory animals (47 pedicle and 7 free) and 54 myocutaneous (32 pedicle and 22 free). The anatomical characteristics of the dorsal flap in the rabbit are presented and the microsurgical technique utilized in elaborating free flaps are described. In comparing survival of the different flap types, a greater survival rate (p < 0.05) was found for myocutaneous than cutaneous; and for pedicle than free flaps. In addition it was verified than arterial flow is indispensable for flap survival.

Animals↗
PubMed1994

[Dorsal flap in laboratory animals. Prediction of its viability].

Various types of flaps were fashioned in the dorsal area of laboratory animals (rabbits). Subjective and objective methods were evaluated as means of prediction of flap viability: superficial cutaneous temperature and cutaneous fluorescence test. It was verified that subjective methods served to help prognosticate flap viability, while superficial cutaneous temperature annotations were unreliable as indicators. Finally, the cutaneous fluorescence test was revealed to be an ideal method of predicting the viability of transferred tissue.

Animals↗
PubMed1993

Developmental relationships between hemopoiesis and vasculogenesis.

Using avian chimeras, we have demonstrated earlier that the stem cells seeding the definitive hemopoietic organs form within the embryo rather than in the yolk sac. We now report experimental evidence indicating that hemopoietic progenitors appear in mouse embryos in the para-aortic splanchnopleura, a location similar to the one that produces stem cells in avian embryos. This structure obtained from E8.5 embryos was grafted under the kidney capsule of adult SCID mice. One compartment of the B lymphoid system became reconstituted with cells derived from the graft, that were identified with genetic and antigenic markers. In vitro data are also in favor of the production of progenitors from this structure. Finally a strategy designed to understand the developmental links between the endothelial network and hemopoietic cells is described. It is based on the expression patterns of two protooncogenes, c-ets1 and c-myb, activated during the amplification period of each of these lineages.

Animals↗
PubMed1992

On the origin of natural IgM in immunoglobulin transgenic mice.

Surface transgenic IgM was expressed by > 95% of small resting splenic B cells but only by 50% of CD5+ and CD5- peritoneal B cells from the mu-transgenic mouse line M54. Transgenic male M54 were crossed with female CBA/N mice carrying the Xid defect. Offspring F1 animals carrying the transgene were analysed for the presence of transgenic and endogenous IgM expressed both in the serum as well as on the surface of splenic and peritoneal B cells. We found that the levels of serum IgM coded for by the transgene were similar in both F1 male, which lack CD5 B cells, and female transgenic mice, which have CD5 B cells. Thus, the Xid defect does not influence the expression of the transgene at the level of naturally activated plasma cells, a finding substantiated by the fact that both male and female naturally activated splenic plasma cells express the transgene at the same frequency. F1 hybrid mice, like transgenic C57BI/6 M54 mice, have naturally activated splenic plasma cells that overexpress endogenous IgM coded for by the VH gene family Q52. The data indicate that normal serum IgM is not derived from CD5+ B cells and that the serum IgM coded for by the mu-transgene from M54 is produced at normal levels even in the male F1 mouse which lacks CD5+ B cells.

Animals↗
PubMed1991

Normal serum immunoglobulins influence the numbers of bone marrow pre-B and B cells.

The homeostatic mechanisms controlling B lymphocyte output from bone marrow are not well understood. The present experiments evaluated putative influences of circulating immunoglobulins (Ig) on bone marrow (BM) pre-B and B cell populations. Injections into normal mice of Ig isolated from normal mouse serum, resulted in a dose-dependent and reversible reduction in numbers of BM B lineage cells, in particular of small B220+ surface IgM- cells. Maximal effects were observed upon injection of isologous polyclonal Ig and were independent of mature T cells. These results suggest a feedback modulation of peripheral Ig on cellular activities in BM B lineage compartments, mediated by mechanisms that seem to involve the variable regions of the Ig molecule.

Animals↗
PubMed1990

Lignans and other constituents from South and central american zanthoxylum species.

Eight lignans (+/-)-syringaresinol, (-)-pinoresinol, (+)-sesamin, (+)-eudesmin, (+)-epieudesmin, (-)-asarinin, (-)-matairesinol, (-)-kobusin, two terpenes lupeol, beta-sitosterol, one aliphatic unsaturated amide, hydroxy-gamma-sanshoöl, and one alkaloid, magnoflorine, were isolated from ZANTHOXYLUM species of Central and South America. Their structures were elucidated mainly by (1)H-, (13)C-NMR, and mass spectroscopy.

Journal Article↗