PubMed Health⌕ Search

Biomedical subjects

J Guzmán

Publications and source records attributed to J Guzmán.

At least 19 recordsLinked to original sources
PubMed2006

[Juxtapapillary capillary hemangioma and central serous retinopathy: description of a case with spontaneous resolution].

CASE REPORT: A patient presented with a unilateral decrease of visual acuity and was found to have a juxtapapillary capillary hemangioma by ophthalmoscopy (confirmed by fluorescein angiography) and atrophy in the retinal pigmentary epithelium with leakage points suggesting bilateral central serous retinopathy. Spontaneous resolution of the hemangioma, as well as the central serous retinopathy, subsequently occurred. DISCUSSION: The decrease of visual acuity in a patient with a juxtapapillary capillary hemangioma has been associated with complications from the lesion itself, but an association of central serous retinopathy, as a possible predisposing factor, has not been previously described.

Fluorescein Angiography↗
PubMed2003

Azotobacter vinelandii mutants that overproduce poly-beta-hydroxybutyrate or alginate.

Azotobacter vinelandii produces two polymers of industrial importance, i.e. alginate and poly-beta-hydroxybutyrate (PHB). Alginate synthesis constitutes a waste of substrate when seeking to optimize PHB production and, conversely, synthesis of PHB is undesirable when optimizing alginate production. In this study we evaluated the effect of a mutation in algA, the gene encoding the enzyme that catalyzes the first step of the alginate biosynthetic pathway in the production of PHB. We also evaluated production of alginate in strain AT6 carrying a phbB mutation that impairs PHB synthesis. The algA mutation prevented alginate production and increased PHB accumulation up to 5-fold, determined in milligrams per milligram of protein. Similarly, the phbB mutation increased alginate production up to 4-fold.

Acyltransferases↗
PubMed2003

Morphological hysteresis of the small airways.

The resistance to airflow that develops in most obstructive processes takes place in the small airways. The aim of the present paper is to describe bronchial hysteresis morphometrically in a respiratory cycle model. As a working hypothesis, it is proposed that the changes that take place in the respiratory tract during the respiratory cycle are related to the bronchial size. Specimen rat lungs were organized into five groups: In the first group, the lungs were filled with a liquid fixative to 25 cm of H2O transpulmonary pressure. The following four groups were inflated with air and fixed through the pulmonary artery. Groups 2 and 3 were fixed at 10 and 20 cm transpulmonary pressure in inflation. The last two groups were fixed in deflation and, for this purpose, the transpulmonary pressure was increased to 27 cm and decreased to 20 and 10 cm, respectively. The lungs were processed for morphometrical study and the following variables were quantified: pulmonary volume, internal area, internal perimeter, wall area, internal area radius and bronchial wall radius. The diameter of the airways studied varied between 84.06 microm and 526.4 microm. The results were classified into three subgroups consisting of small, medium-sized and large bronchi. With a single exception--the internal area in the medium-sized bronchi inflated to 20 cm--all the results obtained in deflation were higher than those obtained in inflation. The internal area increased or decreased significantly upon raising or lowering the transpulmonary pressure respectively, in the small and medium-sized bronchi. The wall area in the large bronchi showed significant differences between inflation and deflation at 10 and 20 cm transpulmonary pressure. The wall area was modified significantly in the lungs fixed at 20 cm in the small bronchi and at 10 cm in medium-sized bronchi. The bronchial wall radius was significantly greater in the large bronchi and smaller in the small bronchi. The lumen of the medium-sized and small bronchi increases in inspiration and decreases in expiration. The wall thickness displayed differences between inflation and deflation. The most marked hysteresis was presented by the bronchial wall in the large bronchi. Our results suggest that the behavior of the bronchi varies according to their size.

Animals↗
PubMed2002

Multidisciplinary bio-psycho-social rehabilitation for chronic low back pain.

BACKGROUND: Chronic low back pain is, in many countries, the main cause of long term disability in middle age. Patients with chronic low back pain are often referred for multidisciplinary treatment. Previous published systematic reviews on this topic included no randomised controlled trials and pooled together controlled and non-controlled studies. OBJECTIVES: To assess the effect of multidisciplinary bio-psycho-social rehabilitation on pain, function, employment, quality of life and global assessment outcomes in subjects with chronic disabling low back pain. SEARCH STRATEGY: We searched MEDLINE, EMBASE, PsychLIT, CINAHL, Health STAR, and The Cochrane Library from the beginning of the database to June 1998 using the comprehensive search strategy recommended by the Back Review Group of the Cochrane Collaboration. INTERVENTION specific key words for this review were: patient care team, patient care management, multidisciplinary, interdisciplinary, multiprofessional, multimodal, pain clinic and functional restoration. We also reviewed reference lists and consulted the editors of the Back Review Group of the Cochrane Collaboration. SELECTION CRITERIA DESIGN: randomised controlled trials comparing multidisciplinary bio-psycho-social rehabilitation with a non-multidisciplinary control intervention. POPULATION: Adults with disabling low back pain of more than three months in duration. INTERVENTION: Patients had to be assessed and treated by qualified professionals according to a plan that addresses physical and at least one of psychological, or social/occupational dimensions. OUTCOMES: Only trials which reported treatment effect in at least one of pain, function, employment status, quality of life or global improvement. Exclusion: Pure educational interventions (back schools) and pure physical interventions were excluded. DATA COLLECTION AND ANALYSIS: Selection, data extraction and quality grading of studies was done by two independent reviewers using pre-tested data forms. Study quality was assessed according to the scheme recommended by the Back Review Group of the Cochrane Collaboration. Trials with internal validity scores of five or more in a ten point scale were considered high quality. Discrepancies between reviewers were resolved by consensus or by a third reviewer. Given the marked heterogeneity in study settings, interventions and control groups we decided not to pool trial results in a meta-analysis. Instead, we summarized findings by strength of evidence and nature of intervention and control treatments. The evidence was judged to be strong when multiple high quality trials produced generally consistent findings. It was judged to be moderate when multiple low quality or one high quality and one or more low quality trials produced generally consistent findings. Evidence was considered to be limited when only one randomised trial existed or if findings of existing trials were inconsistent. MAIN RESULTS: Ten trials (12 randomised comparisons) were included. They randomised a total of 1964 patients with chronic low back pain. There was strong evidence that intensive multidisciplinary bio-psycho-social rehabilitation with a functional restoration approach improved function when compared with inpatient or outpatient non-multidisciplinary treatments. There was moderate evidence that intensive multidisciplinary bio-psycho-social rehabilitation with a functional restoration approach improved pain when compared with outpatient non-multidisciplinary rehabilitation or usual care. There was contradictory evidence regarding vocational outcomes of intensive multidisciplinary bio-psycho-social intervention. Some trials reported improvements in work readiness, but others showed no significant reduction in sickness leaves. Less intensive outpatient psycho-physical treatments did not improve pain, function or vocational outcomes when compared with non-multidisciplinary outpatient therapy or usual care. Few trials reported effects on quality of life or global assessments. REVIEWER'S CONCLUSIONS: The reviewed trials provide evidence that intensive multidisciplinary bio-psycho-social rehabilitation with a functional restoration approach improves pain and function. Less intensive interventions did not show improvements in clinically relevant outcomes.

Back Pain↗
PubMed2002

Pressure volume curve and alveolar recruitment/de-recruitment. A morphometric model of the respiratory cycle.

HYPOTHESIS: The changes in pulmonary volume taking place during respiration are accompanied by the opening and closing of the alveoli, with the number of alveoli open, at the same transpulmonary pressure (TPP) differing, depending on whether the lung is insufflated or deflated. MATERIAL AND METHODS: Seventy 344 Fischer rats divided into five groups. Group 1 lungs were fixed by instilling 10% formalin through the trachea to a pressure of 25 cm H2O. The lungs of the next four groups were air-filled and fixed via the pulmonary artery: group 2 lungs were fixed in inflation at 10 cm H2O TPP; group 3 lungs were fixed in inflation at 20 cm. H2O TPP; the lungs of groups 4 and 5 were fixed in deflation and, therefore, were inflated with air up to 27 cm. H2O to drop to 20 cm in group 4 and to 10 cm in group 5. The lungs were processed for light microscopy, carrying out a morphometric study. The results were statistically processed. RESULTS: The lungs insufflated with liquid fixative at 25 cm of TPP reached higher values in the variables Pulmonary Volume, Internal Alveolar Surface (IAS) and Number of Alveoli, being statistically significant (p < 0.05) in comparison with the other four groups. In the lungs fixed in deflation, the pulmonary volume, IAS and number of alveoli were greater than in those fixed in inflation. The lungs fixed to 20 cm in deflation displayed significant statistical differences compared with those fixed to 20 cm in inflation. The IAS and number of alveoli gave good rates in relation with the pulmonary volume (r > or = 0.65). Three variables were used to measure the size of the alveoli, alveolar cord, alveolar surface and Lm, but none showed significant modifications. CONCLUSION: This study supports the hypothesis that changes in lung volume are related to the increase/decrease in the number of alveoli that are open/closed and not to the modification in the size of the alveoli. Alveolar recruitment is the microscopic expression of pulmonary hysteresis, since the number of alveoli open in deflation is greater than the number open during inflation.

Animals↗
PubMed2001

Multidisciplinary rehabilitation for chronic low back pain: systematic review.

OBJECTIVE: To assess the effect of multidisciplinary biopsychosocial rehabilitation on clinically relevant outcomes in patients with chronic low back pain. DESIGN: Systematic literature review of randomised controlled trials. PARTICIPANTS: A total of 1964 patients with disabling low back pain for more than three months. MAIN OUTCOME MEASURES: Pain, function, employment, quality of life, and global assessments. RESULTS: Ten trials reported on a total of 12 randomised comparisons of multidisciplinary treatment and a control condition. There was strong evidence that intensive multidisciplinary biopsychosocial rehabilitation with functional restoration improves function when compared with inpatient or outpatient non-multidisciplinary treatments. There was moderate evidence that intensive multidisciplinary biopsychosocial rehabilitation with functional restoration reduces pain when compared with outpatient non-multidisciplinary rehabilitation or usual care. There was contradictory evidence regarding vocational outcomes of intensive multidisciplinary biopsychosocial intervention. Some trials reported improvements in work readiness, but others showed no significant reduction in sickness leaves. Less intensive outpatient psychophysical treatments did not improve pain, function, or vocational outcomes when compared with non-multidisciplinary outpatient therapy or usual care. Few trials reported effects on quality of life or global assessments. CONCLUSIONS: The reviewed trials provide evidence that intensive multidisciplinary biopsychosocial rehabilitation with functional restoration reduces pain and improves function in patients with chronic low back pain. Less intensive interventions did not show improvements in clinically relevant outcomes.

Chronic Disease↗
PubMed2001

Surfing for back pain patients: the nature and quality of back pain information on the Internet.

STUDY DESIGN: A prospective, systematic review of web sites related to back pain. OBJECTIVE: To assess the nature and quality of back pain-related information on the World Wide Web during a 2-year period. SUMMARY OF BACKGROUND DATA: The Internet has become a rich source of medical information. Limited knowledge is available, however, about the quality of online resources. Although previous systematic reviews on medical-related web sites found problems in varying degrees with the credibility of information, no such review was conducted to assess the back pain-related sites. METHODS: A search of web sites was conducted in November 1996 using five search engines (AltaVista, Infoseek, Lycos, Yahoo, and Magellan) and two key terms ("back pain" and "back problems"). A sample of sites was evaluated by two independent reviewers. Each site was described by the type and nature of the sponsor, target audience, and content. Overall quality was assessed in terms of evidence-based information available. RESULTS: Seventy-four web sites were reviewed in 1996, and nine of them (12.2%) were identified as high-quality sites. Advertising was the focus of 80.8% of the sites. Eleven sites (14.9%) were found to be discontinued 1 year later, and 20 (27.0%) were not accessible by the reviewers at the 2-year follow-up evaluation. Of the remaining 54 sites, 44.4% were produced by for-profit companies, and most sites targeted people with back pain (63.0%). Only seven out of the nine high-quality sites held their ratings at the 2-year follow-up evaluation. CONCLUSION: Most back pain-related web sites can be classified as advertising. The quality varied considerably, resulting in difficulties for patients to find useful information in this field. The increasing number of people seeking medical information on the Web creates a need for more high quality sites. Further, systematic review of web sites should be encouraged to monitor the accuracy of Internet publication.

Bias↗
PubMed2001

Azotobacter vinelandii aldehyde dehydrogenase regulated by sigma(54): role in alcohol catabolism and encystment.

Encystment in Azotobacter vinelandii is induced by n-butanol or beta-hydroxybutyrate (BHB). We identified a gene, encoding an aldehyde dehydrogenase, that was named aldA. An aldA mutation impaired bacterial growth on n-butanol, ethanol, or hexanol as the sole carbon source. Expression of aldA increased in cells shifted from sucrose to n-butanol and was shown to be dependent on the alternative sigma(54) factor. A mutation in rpoN encoding the sigma(54) factor also impaired growth on alcohols. Encystment on n-butanol, but not on BHB, was impaired in aldA or rpoN mutants, indicating that n-butanol is not an inducer of encystment by itself but must be catabolized in order to induce encystment.

1-Butanol↗
PubMed2000

Colloid in the pituitary pars distalis of viscacha (Lagostomus maximus maximus): ultrastructure and occurrence in relation to season, sex, and growth.

Randomly distributed extracellular colloidal accumulations were observed in the pars distalis of viscacha (Lagostomus maximus maximus). They were preferentially located in the peripheral zone of the gland and showed variability in shape and size. Two different types of colloidal accumulations were found by electron microscopy: 1) those surrounded by nongranulated follicular cells that correspond to characteristic follicles, and 2) those surrounded by granulated cells. In the follicles lined by nongranulated follicular cells, long, prominent microvilli and cytoplasmic processes protruded into the lumen. The frequency of these accumulations varies during the year in adult male animals, showing an increase in number during summer and a decrease during winter. The lowest value was registered in August (winter). The mean follicular diameter did not vary seasonally. The number of colloidal accumulations did not vary seasonally in adult female viscachas, but a significant difference in the mean follicular diameter between pregnant and non-pregnant females was observed. Pituitaries of immature animals contain fewer colloidal accumulations than those of adults. In fetuses, these accumulations were absent. The administration of melatonin provoked a decrease in the number of these structures. The numeric changes of the colloidal accumulations observed in this study are associated with: 1) the seasonal reproductive activity in adult males, and 2) the reproductive condition, body weight and sexual maturity in males and females. The fact that melatonin administration decreases the population of colloidal accumulations in males suggests participation of the pineal gland in these changes.

Age Factors↗
PubMed2000

Antioxidant activity of Artemisia douglasiana besser extract and dehydroleucodine.

The charge (relative concentration) of antioxidants in aqueous extract and dehydroleucodine (DhL) from Artemisia douglasiana Besser was determined employing a procedure based on the quenching of luminol-enhanced chemiluminescence. Total reactive antioxidant potential (TRAP) and total antioxidant reactivity (TAR) values were determined. The data reported in the present work indicate that the extract of Artemisia douglasiana Besser and DhL showed antioxidant capacity. This activity is more pronounced in the extract, suggesting the presence of several antioxidants in Artemisia douglasiana.

Anti-Ulcer Agents↗
PubMed2000

Role of Azotobacter vinelandii mucA and mucC gene products in alginate production.

Azotobacter vinelandii produces the exopolysaccharide alginate, which is essential for its differentiation to desiccation-resistant cysts. In different bacterial species, the alternative sigma factor sigma(E) regulates the expression of functions related to the extracytoplasmic compartments. In A. vinelandii and Pseudomonas aeruginosa, the sigma(E) factor (AlgU) is essential for alginate production. In both bacteria, the activity of this sigma factor is regulated by the product of the mucA, mucB, mucC, and mucD genes. In this work, we studied the transcriptional regulation of the A. vinelandii algU-mucABCD gene cluster, as well as the role of the mucA and mucC gene products in alginate production. Our results show the existence of AlgU autoregulation and show that both MucA and MucC play a negative role in alginate production.

Alginates↗
PubMed2000

The GacS sensor kinase regulates alginate and poly-beta-hydroxybutyrate production in Azotobacter vinelandii.

Azotobacter vinelandii produces two polymers: the extracellular polysaccharide alginate and the intracellular polyester poly-beta-hydroxybutyrate (PHB). A cosmid clone (pSMU588) from an A. vinelandii gene library diminished alginate production by A. vinelandii mucoid strain ATCC 9046. The nucleotide sequence and predicted amino acid sequence of the locus responsible for the mucoidy suppression revealed 65% identity to Pseudomonas GacS, a transmembrane sensor kinase of the two-component regulators, whose cognate response regulator, GacA, is a global activator regulating several products and virulence factors. Plasmid pMC15, harboring gacS, and a strain carrying a gacS nonpolar mutation were constructed. Either pMC15 or the gacS mutation significantly reduced alginate production and transcription of algD, the gene coding for the key enzyme GDP-mannose dehydrogenase of the alginate biosynthetic pathway. We found that the gacS mutation also reduced PHB accumulation and impaired encystment. Taken together, these data indicate that in A. vinelandii the gacSA global system regulates polymer synthesis.

Alginates↗
PubMed2000

Changes in gastroduodenal 5-hydroxytryptamine-containing cells induced by dehydroleucodine.

In previous work, we demonstrated that dehydroleucodine (DhL), a lactone isolated from Artemisia douglasiana Besser, prevents gastroduodenal damage induced by absolute ethanol (EtOH). The present study examined the effects of DhL - applied alone or before EtOH - on gastroduodenal cells containing 5-hydroxytryptamine (5-HT), to clarify the mechanism of action of the drug. Mice were divided into four groups: (I) control; (II) DhL; (III) EtOH, and (IV) DhL + EtOH. Stomachs and duodena were studied by immunohistochemistry and image analysis. EtOH decreased the immunopositive cell number and the area occupied by these cells. This effect was prevented by DhL. DhL alone did not affect the gastric immunopositive cell number and area. Duodena treated only with DhL exhibited a reduction of immunopositive cell number, but no change in area was observed. We propose that the drug probably inhibits the release of the inflammatory mediator 5-HT from endocrine cells, acting as a 'cell stabilizer' in response to injury.

Animals↗
PubMed2000

Acute abdomen and lupus enteritis: thrombocytopenia and pneumatosis intestinalis as indicators for surgery.

Bowel symptoms occur often in systemic lupus erythematosus (SLE), but enteric complications in patients on steroid therapy are rare. We report a case of a 14-year-old Mexican girl with SLE on high-dose steroid therapy complicated by abdominal vasculitis and small bowel perforation. Accompanying this serious complication were thrombocytopenia and radiographic changes of pneumatosis intestinalis. These findings suggested necrotizing enteritis and prompted urgent surgery. Four jejunal perforations, pneumatosis intestinalis, and submucosal vasculitis were present in the resected specimen. Persistent SLE activity responded to cyclophosphamide, which is indicated in patients with digestive symptoms who fail to respond to high-dose steroids.

Abdomen, Acute↗
PubMed2000

Effect of flumazenil on electroencephalographic patterns induced by midazolam.

BACKGROUND: Flumazenil is a competitive benzodiazepine receptor antagonist, reverts the sedation effects of benzodiazepines and its effect on electroencephalographic (EEG) patterns is controversial. The purpose of this study was to describe flumazenil's effect on EEG patterns of patients undergoing conscious sedation. METHODS: Ten voluntary patients, aged 16-23, at elective oral surgery had conscious sedation with midazolam and local anesthesia. After the procedure, sedation was reversed with flumazenil. Each patient had 4 EEGs of 4 minutes each: baseline, 5 minutes after midazolam, prior to flumazenil, and 8 minutes after flumazenil. A clinical neurophysiologist interpreted EEGs blinded to time. RESULTS: Eight patients had an awake and 2 had an awake and drowsy normal EEG. After midazolam all developed a diffuse beta wave and alpha wave attenuation or dropout. Prior to flumazenil 7 presented diffuse beta and scattered theta waves, and 3 an awake pattern (procedure required > 30 minutes). After flumazenil, reversal of beta and theta waves and appearance of alpha waves was noted; no changes occurred when procedure lasted more than 30 minutes. One patient presented with diffuse theta waves, 6 Hz. CONCLUSIONS: Flumazenil reverts midazolam EEG changes if administered < 30 minutes after midazolam administration, midazolam-induced EEG changes revert spontaneously after 30 minutes, and flumazenil may precipitate theta activity.

Adolescent↗
PubMed2000

Can biomedical researchers benefit from political science methodologists?

The purpose of this monograph is to introduce the work of a group of political science methodologists, who created a series of models for estimation and prediction. It refers to the work of Gary King and his collaborators at Harvard University's Department of Government. They developed a set of computer-intensive simulation techniques, along with the corresponding public domain software. Their paper, "Making the most of statistical analyses: improving interpretation and presentation." and the corresponding software, Clarify (Tomz et al., 1999) are the basic sources. The use of statistical simulation has become a standard practice with the advent of fast and low cost modern computing. The reader can appreciate the usefulness in biomedical research of Clarify. It can be of much help on the statistical analysis of many biomedical problems.

Politics↗
PubMed1999

Transcriptional organization of the Azotobacter vinelandii algGXLVIFA genes: characterization of algF mutants.

Azotobacter vinelandii forms desiccation-resistant cysts which contain a high proportion of the exopolysaccharide alginate in their envelope. We have previously shown that the A. vinelandii alginate biosynthetic genes algA and algL are transcribed from a promoter located somewhere upstream of algL. In this study we sequenced the A. vinelandii algX, algL, algV, algI and algF genes located between algG and algA. We carried out primer extension analysis of the algG, algX and algL genes and detected transcription start sites upstream algG but not upstream algX or algL, implying that algG and algX form part of the previously identified algL-A operon. A promoter upstream algA was also detected; however, transcription of algA exclusively from this promoter is not sufficient for the AlgA levels required for alginate production. An algF mutant (AJ34) was constructed by insertion of the Omega-tetracycline cassette in the non-polar orientation. As expected, AJ34 produced unacetylated alginate. Viability of 35day old cysts formed by strain AJ34, but not of those formed by the wild type, was reduced, indicating that acetylation of alginate plays a role in cyst resistance to desiccation.

Alginates↗