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Biomedical subjects

M Cifuentes

Publications and source records attributed to M Cifuentes.

At least 19 recordsLinked to original sources
PubMed2006

Hospital injury rates in relation to socioeconomic status and working conditions.

OBJECTIVES: To describe the risk of work injury by socioeconomic status (SES) in hospital workers, and to assess whether SES gradient in injury risk is explained by differences in psychosocial, ergonomic or organisational factors at work. METHODS: Workforce rosters and Occupational Safety and Health Administration injury logs for a 5-year period were obtained from two hospitals in Massachusetts. Job titles were classified into five SES strata on the basis of educational requirements and responsibilities: administrators, professionals, semiprofessionals, skilled and semiskilled workers. 13 selected psychosocial, ergonomic and organisational exposures were assigned to the hospital jobs through the national O*NET database. Rates of injury were analysed as frequency records using the Poisson regression, with job title as the unit of analysis. The risk of injury was modelled using SES alone, each exposure variable alone and then each exposure variable in combination with SES. RESULTS: An overall annual injury rate of 7.2 per 100 full-time workers was estimated for the two hospitals combined. All SES strata except professionals showed a significant excess risk of injury compared with the highest SES category (administrators); the risk was highest among semiskilled workers (RR 5.3, p<0.001), followed by nurses (RR 3.7, p<0.001), semiprofessionals (RR 2.9, p = 0.006) and skilled workers (RR 2.6, p = 0.01). The risk of injury was significantly associated with each exposure considered except pause frequency. When workplace exposures were introduced in the regression model together with SES, four remained significant predictors of the risk of injury (decision latitude, supervisor support, force exertion and temperature extremes), whereas the RR related to SES was strongly reduced in all strata, except professionals. CONCLUSIONS: A strong gradient in the risk of injury by SES was reported in a sample population of hospital workers, which was greatly attenuated by adjusting for psychosocial and ergonomic workplace exposures, indicating that a large proportion of that gradient can be explained by differences in working conditions.

Accidents, Occupational↗
PubMed2003

Bone turnover and body weight relationships differ in normal-weight compared with heavier postmenopausal women.

Low body weight is associated with increased risk for fractures, whereas higher body weight has been shown to be protective against osteoporosis. This study evaluated whether body weight plays a role regulating bone turnover and mass in normal-weight (body mass index (BMI) <25 kg/m2), overweight (BMI 25-29.9 kg/m2) and obese (BMI> or =30 kg/m2) postmenopausal women who were either receiving hormone replacement therapy [HRT(+)] or not [HRT(-)] (total of six groups). Body weight, BMI, total body bone mineral content (TBBMC), and markers of bone formation (serum osteocalcin) and bone resorption (urinary pyridinoline (PYD) and deoxypyridinoline) were retrospectively analyzed in 210 postmenopausal women. The mean age was 67+/-6 years, with mean body weight of 70.8+/-14.2 kg, ranging from 45.0 to 115.5 kg. Body weight was positively correlated with TBBMC ( r=0.50, p<0.0001). There was a lower TBBMC and higher bone formation rate in normal-weight than obese HRT(-) women, but in women taking HRT there were no differences between BMI categories. In addition, in normal-weight HRT(-) women only, PYD and body weight showed a negative correlation (r=-0.39, p=0.01). Among normal-weight, but not overweight or obese subjects, we observed higher TBBMC and lower bone turnover in the HRT(+) compared with the HRT(-) group. Regression models explained 36% of the variance in TBBMC, mainly through body weight. Additional models could only explain 11-15% of the variance in bone turnover. Taken together, these data suggest that among normal-weight but not obese postmenopausal women, higher bone turnover is associated with lower bone mass, and that only normal-weight women show a different bone turnover profile with HRT treatment. Body weight should be considered an important factor in bone metabolism with relevant clinical implications.

Aged↗
PubMed2003

Osteopontin facilitates bone resorption, decreasing bone mineral crystallinity and content during calcium deficiency.

Osteopontin null-mice were previously shown to have bones containing more mineral and larger mineral crystals. These bones were independently seen to be resistant to ovariectomy-induced remodeling. To separate the physicochemical effects of osteopontin, which is an in vitro inhibitor of mineral crystal formation and growth, from effects of osteopontin on in vivo bone remodeling, this study examined mature (5-month-old) osteopontin-null (Opn-/-) and wildtype (WT) mice given a calcium-deficient diet. Biochemical parameters were measured during 4 weeks of Ca deficiency, followed by 1 week of refeeding adequate Ca. Ca deficiency caused a transiently greater rise in bone resorption in WT than Opn-/- mice (P = 0.01), whereas only the Opn-/- mice tended to increase Ca absorption (P = 0.08), yet both groups showed elevated levels of parathyroid hormone (PTH) (P < 0.001). The rise in markers of bone formation due to Ca deficiency was similar in both groups during Ca deficiency. Fourier transform infrared microspectroscopy assessed mineral properties at 20 microm spatial resolution in different anatomic regions of the bone. The Ca-deficient Opn-/- animals had slightly increased mineral content as compared to the WT, and there was a significant increase in the mineral content of older (endosteal) bone, implying that osteoclast recruitment was impaired. Crystallinity in the Ca-deficient Opn-/- bones was increased relative to the Ca-deficient WT at all sites except adjacent to the periosteum (younger mineral). These data suggest that osteopontin has both a physicochemical effect (inhibiting crystal growth and crystal proliferation) and a role in osteoclast recruitment, and in its absence, extraskeletal organs maintain calcium homeostasis.

Amino Acids↗
PubMed2003

Neurogenesis in explants from the walls of the lateral ventricle of adult bovine brain: role of endogenous IGF-1 as a survival factor.

Previous studies have shown the existence of proliferating cells in explants from bovine (Bos Taurus) lateral ventricle walls that were maintained for several days in vitro in the absence of serum and growth factors. In this study we have characterized the nature of new cells and have assessed whether the insulin-like growth factor-1 (IGF-1) receptor regulates their survival and/or proliferation. The explants were composed of the ependymal layer and attached subependymal cells. Ependymal cells in culture were labelled with glial markers (S-100, vimentin, GFAP, BLBP, 3A7 and 3CB2) and did not incorporate bromodeoxiuridine when this molecule was added to the culture media. Most subependymal cells were immunoreactive for beta III-tubulin, a neuronal marker, and did incorporate bromodeoxiuridine. Subependymal neurons displayed immunoreactivity for IGF-1 and its receptor and expressed IGF-1 mRNA, indicating that IGF-1 is produced in the explants and may act on new neurons. Addition to the culture media of an IGF-1 receptor antagonist, the peptide JB1, did not affect the incorporation of bromodeoxiuridine to proliferating subependymal cells. However, JB1 significantly increased the number of TUNEL positive cells in the subependymal zone, suggesting that IGF-1 receptor is involved in the survival of subependymal neurons. In conclusion, these findings indicate that neurogenesis is maintained in explants from the lateral cerebral ventricle of adult bovine brains and that IGF-1 is locally produced in the explants and may regulate the survival of the proliferating neurons.

Age Factors↗
PubMed2001

Analysis and quantification of the secretory products of the subcommissural organ by use of monoclonal antibodies.

Bovine Reissner's fiber (RF) glycoproteins were used as antigen for the production of polyclonal and monoclonal antibodies (Mabs). We also produced Mabs against intracellular secretory glycoproteins of the bovine subcommissural organ (SCO). These Mabs were used for immunodetection of secretory proteins in situ (structural and ultrastructural immunocytochemistry), in blots, and in solutions. Three different antigen-mediated ELISA were designed to evaluate the affinity of the Mabs, to study the nature of the epitopes, and for competition test among Mabs. Two double antibody sandwich ELISA were designed to detect and quantify soluble secretory materials in different samples, to study coexistence of epitopes, and to elucidate whether epitopes for Mabs are repeated or not in the RF-glycoproteins. Twenty-three Mabs recognizing the bovine RF- and SCO-glycoproteins in solutions (ELISA) as well as in tissue sections, were obtained. Nineteen of these Mabs also recognized the pig SCO, 11 the rabbit SCO, 6 the dog SCO, and 5 the rat SCO. None of the Mabs recognized the SCO of non-mammalian species. The different types of ELISA demonstrated that: (1) the epitopes reside in the proteinaceous moiety of the secretion, (2) they coexist in the same molecular forms and, with few exceptions, they did not overlap, (3) they were not repeated in the secretory molecule(s). Three Mabs were used for immunoblotting of RF; one of them revealed the same band pattern as that shown by an anti-RF serum. It is concluded that all Mabs raised in our laboratory are directed against non-repeated sequences of RF-glycoproteins that have not been conserved in vertebrate phylogeny.

Animals↗
PubMed2001

Searching for specific binding sites of the secretory glycoproteins of the subcommissural organ.

The molecular organization of Reissner's fiber (RF), the structure of its proteins, and the permanent turnover of these proteins are all facts supporting the possibility that RF may perform multiple functions. There is evidence that CSF-soluble RF-glycoproteins may occur under physiological conditions. The present investigation was designed to investigate the probable existence within the CNS of specific binding sites for RF-glycoproteins. Three experimental protocols were used: (1) immunocytochemistry of the CNS of bovine fetuses using anti-idiotypic antibodies, raised against monoclonal antibodies developed against bovine RF-glycoproteins; (2) in vivo binding of the RF glycoproteins, perfusing into the rat CSF 125I-labeled RF-glycoproteins, or grafting SCO into a lateral ventricle of the rat; (3) in vitro binding of unlabeled RF-glycoproteins to rat and bovine choroid plexuses maintained in culture. One of the anti-idiotypic antibody generated by a Mab raised against RF-glycoproteins binds to choroidal cells. Furthermore, binding of RF-glycoproteins to the rat choroid plexus was obtained when: (1) the choroid plexus was cultured in the presence of unlabeled RF-glycoproteins; (2) the concentration of soluble RF-glycoproteins in the CSF was increased by isografting SCOs into a lateral ventricle; (3) radiolabeled glycoproteins were perfused into the ventricular CSF. This evidence suggests that the apical plasma membrane of the ependymal cells of the choroid plexus has specific binding sites for RF-glycoproteins, of unknown functional significance. The radiolabeled RF-glycoproteins perfused into the rat CSF also bound to the paraventricular thalamic nucleus, the floor of the Sylvian aqueduct and of the rostral half of the fourth ventricle, and the meninges of the brain and spinal cord. The labeling of the paraventricular thalamic nucleus points to a functional relationship between this nucleus and the SCO. The possibility that the SCO may be a component of the circadian timing system is discussed.

Animals↗
PubMed2001

Improving medical students' communication with limited-literacy patients: project development and implementation.

BACKGROUND: Physicians may not realize that some of their patients have limited reading abilities. The AMC Cancer Research Center and the Primary Care Curriculum at the University of Colorado collaborated to develop and implement a project to teach medical students to identify and effectively communicate with limited-literacy patients regarding cancer screening. METHOD: The project incorporated two standardized-patient (SP) cases on cancer screening and literacy into the existing curriculum for second-year students. A small-group, interactive problem-based learning (PBL) case on breast cancer screening and literacy introduced the concept of communicating about cancer screening and literacy issues. A clinical practice examination on colorectal cancer screening and literacy was given at the end of the year. RESULTS: The collaborative project proved successful in incorporating literacy and cancer screening into a medical school curriculum. Time spent training SPs to play the role of adults with limited literacy was very important, as was time spent pre-testing the cases. The PBL case effectively promoted group discussion of cancer screening and literacy. CONCLUSION: The project succeeded in making students aware of literacy and cancer screening issues. Outcome results are being analyzed.

Communication↗
PubMed2001

Energy restriction reduces bone density and biomechanical properties in aged female rats.

Bone mineral density (BMD) is highly correlated with body weight, and weight loss is associated with reduced BMD. Whether such losses of BMD increase skeletal fragility is unclear. We examined the effect of 9 wk of energy restriction (ER) on bone density, mineral and matrix protein composition and biomechanical properties in mature (20 wk old, n = 12) and aged (48 wk old, n = 16) female rats. Energy-restricted rats were fed 40% less energy than controls that consumed food ad libitum. Bone content of mineral (ash and calcium content) and matrix proteins (hydroxyproline, pyridinium crosslinks and proteoglycans), serum hormones, site-specific bone density and biomechanical properties (peak load, peak torque, shear stiffness and bending stiffness) were measured at the conclusion of the study. In both age groups, ER reduced body weight by 15 +/- 10% (P < 0.001) and dramatically decreased femoral bone density by 32-35% (P < 0.01) compared with controls. Energy restriction resulted in a small reduction in tibia and humerus density, as well as biomechanical properties in the aged but not mature rats (P < 0.05). Reduced serum levels of insulin and estradiol due to ER in aged rats (P < 0.05) may play a role in altering bone quality. These data show that although weight loss due to ER is detrimental to some bone parameters in mature rats, only aged rats show consistent reductions in bone density and biomechanical properties.

Aging↗
PubMed2001

Personalized remedial intensive training of one medical student in communication and interview skills.

BACKGROUND: Medical students found to be deficient in communication and interview skills pose a difficult remediation challenge. There is no standard way to address such deficiencies. The authors describe the development and implementation of an intensive remedial curriculum. DESCRIPTION: A 2nd-year student found deficient in communication skills was held back for a year and paired with a clinical preceptor for intensive skills training, including a weekly precepted clinic, structured readings, standardized patient (SP) exercises, communications workshops, and end-of-year standardized clinical evaluations. EVALUATION: The student's self-assessment and the preceptor's assessments of communication skill gradually improved over the year. The student improved through a progression of SP exercises focusing on specific communication skills. The student passed a final evaluation exercise with an excellent rating from the SP and the preceptor. CONCLUSIONS: This multistrategy approach to improve communication skills can be applied to other students and in other institutions. Based on the Bayer Institute communication workshops and integrated coaching techniques, the material forms a framework to help deficient students to become proficient in communication and interviewing skills.

Communication↗
PubMed2000

Ependymal explants from the lateral ventricle of the adult bovine brain: a model system for morphological and functional studies of the ependyma.

By gently scraping off the surface of the lateral ventricles of adult bovine brains, we obtained sheets containing the ependymal layer and some attached sub-ependymal cells. Explants were cultured in serum-free medium or in two media enriched with 20% fetal calf serum or 20% adult bovine cerebrospinal fluid, and processed for different time intervals from 4 h to 60 days. For characterization of the ependymal cells we used antisera against S-100 protein, vimentin and glial fibrillary acidic protein (GFAP). For comparison, the ependyma of adult bovines and of fetuses from days 60 to 120 post coitum was studied in situ. The adult ependyma consisted of a ciliated, cuboid cell monolayer with short basal processes; it displayed S-100 immunoreactivity but only scarce deposits of vimentin and no GFAP. The fetal ependyma had the appearance of a pseudostratified epithelium with elongated nuclei and basal processes containing S-100 and vimentin from day 80 post coitum and GFAP from day 100 post coitum. In explants, no differences were seen between the three culture media; the ependyma became pseudostratified, developed basal processes and showed increasing amounts of S-100 and vimentin first, and subsequently also GFAP. These changes were concomitant with the onset of mitotic activity in the subependymal layer leading to the production of numerous cells. The morphological and immunocytochemical features of ependymal cells in cultured explants resembled those of fetal ependyma. Our results indicate that the culture of ependymal explants from adult bovine lateral ventricles is an useful model system for morphological and functional studies of the ependyma and for the analysis of cell proliferation in the subependymal layer.

Age Factors↗
PubMed1999

[Nutritional status and energy expenditure in elders of differing socioeconomic level].

BACKGROUND: Income and socioeconomic status can influence nutritional status of individuals. Since elders are a more vulnerable group to nutritional deficiencies, socioeconomic status could have a special relevance on nutrition of elderly people. AIM: To assess the influence of socioeconomic status on the nutritional status of elders. MATERIAL AND METHODS: Elders of both sexes of high socioeconomic level and age and sex matched elders of low socioeconomic status were studied. Anthropometry, body composition using double beam X ray absorptiometry, resting energy expenditure using an open circuit indirect calorimeter, routine biochemistry, blood levels of folic acid, vitamin B12 and homocysteine were measured in all subjects. RESULTS: Fourteen female elders of high socioeconomic level, 14 females of low level and 12 males of each level were studied. Mean age of females and males was 71.5 +/- 3.7 and 73.9 +/- 4.2 years old respectively. Males and females of high socioeconomic status were taller than their counterparts of low status. Females of high socioeconomic status had a lower body mass index than their pairs of low status (26.3 +/- 3.8 and 30.2 +/- 5.6 kg/m2 respectively p < 0.02). Men of high economic status had a higher fat mass than their pairs of low level (20.3 +/- 3.5 and 15.1 +/- 5.5 kg respectively, p < 0.005). No differences in resting energy expenditure in women of differing socioeconomic level were observed. Men of high level had a higher energy expenditure that their counterparts of low level (36.0 +/- 4.9 and 32.8 +/- 2.2 Kcal/kg lean body mass/day respectively, p < 0.02). Low level male elders had higher serum total cholesterol and triglycerides. Folic acid, vitamin B12 and homocysteine levels were within normal limits. Dietary intake showed deficiencies in calorie, protein and vitamin intake in all subjects. CONCLUSIONS: In this group of elders, low socioeconomic level did not produce a significant impact on nutritional status.

Absorptiometry, Photon↗
PubMed1999

[Emergence of resistance to macrolides in Streptococcus pyogenes].

BACKGROUND: Diseases produced by Streptoccocus pyogenes are still a problem in Chile, as in the rest of the world. It exhibits in vitro susceptibility to different antimicrobials, but penicillin continues to be the treatment of choice. Alternative drugs have been developed for allergic patients, such as erythromycin, new macrolides and cephalosporins. Nevertheless, resistant strains are appearing due to the indiscriminate use of macrolides. AIM: To assess present antimicrobial susceptibility of S Pyogenes strains isolated from chilean patients. MATERIAL AND METHODS: The susceptibility to penicillin, macrolides, clindamycin, cephalotin and vancomycin of 153 S Pyogenes strains, obtained from different health centers of the Metropolitan Region and isolated between 1996 and 1998, was assessed using the Kirby-Bauer method. Agar dilution minimal inhibitory concentration was then determined to macrolide resistant strains. RESULTS: All strains were susceptible to penicillin. There was a 7.2% cross-resistance to macrolides. CONCLUSIONS: These results confirm that S Pyogenes resistance to macrolides has increased considerably in the Metropolitan Region of Chile during the last years.

Anti-Bacterial Agents↗
PubMed1998

Neuraminidase injected into the cerebrospinal fluid impairs the assembly of the glycoproteins secreted by the subcommissural organ preventing the formation of Reissner's fiber.

Neuraminidase was injected into the cerebrospinal fluid of normal rats to investigate the assembly and fate of the desialylated Reissner's fiber glycoproteins. It was established that a single injection of neuraminidase cleaved the sialic acid residues of the Reissner's fiber glycoproteins that had been assembled before the injection, and of the molecules that were released over a period of at least 4 h after the injection. These desialylated glycoproteins underwent an abnormal assembly that led to the formation of spheres instead of a fiber. The number of these spheres increased during the 4-h period following the injection, indicating that neuraminidase did not prevent the secretion of the Reissner's fiber glycoproteins into the cerebrospinal fluid. The spheres remained attached to the surface of the subcommissural organ and became intermingled with infiltrating cells, many of which were immunocytochemically identified as macrophages. The latter were seen to contain immunoreactive Reissner's fiber material. It is concluded that the desialylated Reissner's fiber glycoproteins forming the spheres underwent an in situ degradation by macrophages, thus resembling the normal process undergone by the Reissner's fiber glycoproteins reaching the massa caudalis.

Animals↗
PubMed1998

Quantification of the secretory glycoproteins of the subcommissural organ by a sensitive sandwich ELISA with a polyclonal antibody and a set of monoclonal antibodies against the bovine Reissner's fiber.

The subcommissural organ (SCO) is an ependymal brain gland that releases glycoproteins into the ventricular cerebrospinal fluid where they condense to form the Reissner's fiber (RF). We have developed a highly sensitive and specific two-antibody sandwich enzyme-linked immunosorbent assay (ELISA) for the quantification of the bovine SCO secretory material. The assay was based on the use of the IgG fraction of a polyclonal antiserum against the bovine RF as capture antibody and a pool of three peroxidase-labeled monoclonal antibodies that recognize non-overlapping epitopes of the RF glycoproteins as detection antibody. The detection limit was 1 ng/ml and the working range extended from 1 to 4000 ng/ml. The calibration curve, generated with RF glycoproteins, showed two linear segments: one of low sensitivity, ranging from 1 to 125 ng/ml, and the other of high sensitivity between 125 and 4000 ng/ml. This assay was highly reproducible (mean intra- and interassay coefficient of variation 2.2% and 5.3%, respectively) and its detectability and sensitivity were higher than those of ELISAs using exclusively either polyclonal or monoclonal antibodies against RF glycoproteins. The assay succeeded in detecting and measuring secretory material in crude extracts of bovine SCO, culture medium supernatant of SCO explants and incubation medium of bovine RF; however, soluble secretory material was not detected in bovine cerebrospinal fluid.

Animals↗
PubMed1998

Spontaneous congenital hydrocephalus in the mutant mouse hyh. Changes in the ventricular system and the subcommissural organ.

The subcommissural organ is an ependymal gland located at the entrance of the cerebral aqueduct. It secretes glycoproteins into the cerebrospinal fluid, where they aggregate to form Reissner's fiber. This fiber grows along the aqueduct, fourth ventricle, and central canal. There is evidence that the subcommissural organ is involved in the pathogenesis of congenital hydrocephalus. This organ was investigated in the mutant mouse hyh developing a congenital hydrocephalus. The central nervous system of normal and hydrocephalic hyh mice, 1 to 40 days old, was investigated using antibodies recognizing the subcommissural organ secretory glycoproteins, and by transmission and scanning electron microscopy. At birth, the affected mice displayed open communications between all ventricles, absence of a central canal in the spinal cord, ependymal denudation of the ventricles, stenosis of the rostral end of the aqueduct, and hydrocephalus of the lateral and third ventricles and of the caudal end of the aqueduct. Around the 5th postnatal day, the communication between the caudal aqueduct and fourth ventricle sealed, and hydrocephalus became severe. It is postulated that the hyh mice carry a genetic defect affecting the ependymal cell lineage. The subcommissural organ showed signs of increased secretory activity; it released to the stenosed aqueduct a material that aggregated, but it did not form a Reissner's fiber. A large area of the third ventricular wall differentiated into a secretory ependyma synthesizing a material similar to that secreted by the subcommissural organ. It is concluded that the subcommissural organ changes during hydrocephalus; whether these changes precede hydrocephalus needs to be investigated.

Aging↗
PubMed1997

Rostral floor plate (flexural organ) secretes glycoproteins immunologically similar to subcommissural organ glycoproteins in dogfish (Scyliorhinus canicula) embryos.

The subcommissural organ of vertebrates secretes glycoproteins into the cerebrospinal fluid of the third cerebral ventricle. This material polymerizes in Reissner's fiber. During ontogenetic development, besides the subcommissural organ, the ependyma lining the pontine flexure constitutes an additional Reissner's fiber-secreting gland named flexural organ. We have studied the secretion of the flexural organ and the subcommissural organ in dogfish (Scyliorhinus canicula) embryos using three different antisera and the lectins concanavalin A and wheat germ agglutinin. AFRU is an antiserum against the bovine Reissner's fiber, Ab-600 is an antiserum against 600 kDa dogfish subcommissural organ glycoproteins; and APSO is an antiserum against immunoaffinity purified bovine subcommissural organ secretory glycoproteins. These three antisera immunostained the flexural organ indicating that it contains epitopes similar to those present in bovine and dogfish subcommissural organ glycoproteins. It seems highly probable that the flexural organ and the subcommissural organ of dogfish embryos secrete similar compound(s). Other ependymal regions were also immunostained with Ab-600 and APSO antisera. Then, Reissner's fiber-like glycoproteins were transiently expressed by most embryonary ependymal cells. These glycoproteins might play a role in the development of the central nervous system of vertebrates.

Animals↗