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Biomedical subjects

R Valencia

Publications and source records attributed to R Valencia.

At least 19 recordsLinked to original sources
PubMed2006

Nosocomial outbreak of Pseudomonas aeruginosa endophthalmitis.

We describe an outbreak of nosocomial endophthalmitis due to a common source, which was determined to be trypan blue solution prepared in the hospital's pharmacy service. We assume that viable bacteria probably gained access to the trypan blue stock solution during cooling after autoclaving. The temporal cluster of Pseudomonas aeruginosa endophthalmitis was readily perceived on the basis of clinical and microbiological findings, and an exogenous source of contamination was unequivocally identified by means of DNA fingerprinting.

Aged↗
PubMed2006

[Feasibility of flat-panel volumetric computed tomography (fpVCT) in experimental small animal imaging of osteoporosis - initial experience].

BACKGROUND: Flat-panel volumetric computed tomography (fpVCT) is a new, noninvasive CT imaging modality with increased isotropic resolution. Technical details, potential applications, and our initial experience with a fpVCT prototype scanner in the imaging of osteoporosis in a rat model are presented. METHODS: To date, 21 rats have been investigated in vivo with fpVCT. Pharmacologic effects on bone mineral density (BMD) and structure were of special interest. Image evaluation focussed on the second lumbar vertebra and the left femoral bone. To validate measurement results, BMD values calculated with fpVCT were correlated with results of BMD measurements from ashing of the second lumbar vertebra and femoral bones. RESULTS: Our initial results show that fpVCT is capable of detecting differences in BMD between ovariectomized rats treated with estradiol and a control group with high statistical significance (p<0.05), corresponding to ashing as the gold standard. CONCLUSIONS: In a rat model, fpVCT imaging is especially useful in longitudinal in vivo investigations of BMD measures. Spatial resolution of up to 150 microm allows imaging of the trabecular structure only in human cadaveric bones.

Animals↗
PubMed2006

[Characteristics and applications of a flat panel computer tomography system].

PURPOSE: To assess a new flat panel volume computed tomography (FP-VCT) with very high isotropic spatial resolution as well as high Z-axis coverage. MATERIALS AND METHODS: The prototype of an FP-VCT scanner with a detector cell size of 0.2 mm was used for numerous phantom studies, specimen examinations, and animal research projects. RESULTS: The high spatial resolution of the new system can be used to accurately determine solid tumor volume, thus allowing for earlier assessment of the therapeutic response. In animal experimentation, whole-body perfusion mapping of mice is feasible. The high spatial resolution also improves the classification of coronary artery atherosclerotic plaques in the isolated post mortem human heart. With the depiction of intramyocardial segments of the coronary arteries, investigations of myocardial collateral circulation are feasible. In skeletal applications, an accurate analysis of the smallest bony structures, e. g., petrous bone and dental preparations, can be successfully performed, as well as investigations of repetitive studies of fracture healing and the treatment of osteoporosis. CONCLUSION: The introduction of FP-VCT opens up new applications for CT, including the field of molecular imaging, which are highly attractive for future clinical applications. Present limitations include limited temporal resolution and necessitate further improvement of the system.

Animals↗
PubMed2002

Temporary shielding of hot spots in the drainage areas of cutaneous melanoma improves accuracy of lymphoscintigraphic sentinel lymph node diagnostics.

Detection of the "true" sentinel lymph nodes, permitting correct staging of regional lymph nodes, is essential for management and prognostic assessment in malignant melanoma. In this study, it was prospectively evaluated whether simple temporary shielding of hot spots in lymphatic drainage areas could improve the accuracy of sentinel lymph node diagnostics. In 100 consecutive malignant melanoma patients (45 women, 55 men; age 11-91 years), dynamic and static lymphoscintigraphy in various views was performed after strict intracutaneous application of technetium-99m nanocolloid (40-150 MBq; 0.05 ml/deposit) around the tumour (31 patients) or the biopsy scar (69 patients, safety distance 1 cm). The images were acquired with and without temporary lead shielding of the most prominent hot spots in the drainage area. In 33/100 patients, one or two additional sentinel lymph nodes that showed less tracer accumulation or were smaller (<1.5 cm) were detected after shielding. Four of these patients had metastases in the sentinel lymph nodes; the non-sentinel lymph nodes were tumour negative. In 3/100 patients, hot spots in the drainage area proved to be lymph vessels, lymph vessel intersections or lymph vessel ectasias after temporary shielding; hence, a node interpreted as a non-sentinel lymph node at first glance proved to be the real sentinel lymph node. In two of these patients, lymph node metastasis was histologically confirmed; the non-sentinel lymph nodes were tumour free. In 7/100 patients the exact course of lymph vessels could be mapped after shielding. In one of these patients, two additional sentinel lymph nodes (with metastasis) were detected. Overall, in 43/100 patients the temporary shielding yielded additional information, with sentinel lymph node metastases in 7%. In conclusion, when used in combination with dynamic acquisition in various views, temporary shielding of prominent hot spots in the drainage area of a malignant melanoma of the skin leads to an improvement in the accuracy of identification and localisation of sentinel lymph nodes by lymphoscintigraphy.

Adolescent↗
PubMed2001

[Alignment of the sagittal profile after surgical therapy of nonspecific destructive spondylodiscitis: ventral or ventrodorsal method--a comparison of outcomes].

From 1989 to 1998, 129 patients underwent surgery for unspecific spondylodiscitis in the Department of Orthopedics of the Free University of Berlin. Fifty-six of them were followed up, and their clinical and radiological results were evaluated in this study. The surgical results of 40 patients with only ventral removal of a focus and defect coverage with an iliac crest graft were compared to those of 16 with additional dorsal bridging instrumentation by internal fixation. A mean of 2.3 vertebrae were fused in ventral spondylodesis; the mean length of dorsal instrumentation by internal fixation was 3.8 vertebrae. Patients were followed up a mean of 5.1 years after surgery. The mean age of patients was 57.1 years at the time of surgery. Patients were postoperatively mobilized a mean of 5 days after ventrodorsal fusion. A purely ventral procedure required a mean postoperative immobilization period of 3.6 weeks and brace fitting of a mean 8.2 months. There was one case of recurrent spondylodiscitis 25 months postoperatively, which made a revision of the focus necessary. The consolidation rate of the ventral spondylodesis was 84-100% in the different subgroups. A differential view of the spinal areas and ventral fusion segments was used to make a statement about the development of the sagittal spine profile. The segmental position of the spine in the sagittal plane was assessed by comparing the segmental kyphosis angles to normal values in the literature. All subgroups submitted to combined ventrodorsal fusion had a greater preoperative segmental kyphosis angle than those undergoing ventral fusion alone. In marked segmental kyphotic false positioning, the combined ventrodorsal procedure achieved good postoperative repositioning results, and an increase in segmental kyphosis was prevented. Ventral removal of a focus and bone graft spondylodesis seem to be adequate in single-level spondylodiskitis especially in the lumbar spine, but additional dorsal instrumentation should be performed in the case of long ventral fusion.

Adolescent↗
PubMed2001

Distribution of C-reactive protein and its relation to risk factors and coronary heart disease risk estimation in the National Health and Nutrition Examination Survey (NHANES) III.

The authors examined the distribution of, and risk factors associated with, the inflammatory marker C-reactive protein (CRP) among a large sample of non-institutionalized American adults aged 30-74 years of age, and its relation to estimated 10-year coronary heart disease risk. The population studied comprised 4472 men and 5212 women aged 30-74 years, without coronary heart disease, who had CRP measurements in the Third National Health and Nutrition Examination Survey (NHANES III). The 10-year risk of coronary heart disease was estimated from Framingham risk factor algorithms among those with CRP levels of less-than-or-equal0.21 mg/dL, >0.21 to <0.5mg/dL, 0.5 to <1.0 mg/dL, and greater-than-or-equal1.0 mg/dL. Mean (SD) levels of CRP were 0.41 (0.64) mg/dL in men and 0.55 (0.91) mg/dL in women. Levels of at least 1 mg/dL were measured in 6.4% of men and 12.9% of women. CRP levels were highest among non-Hispanic black men and Mexican-American women. According to multiple logistic regression analysis, cigarette smoking and increased age, body mass index, and systolic blood pressure in men, and body mass index and diabetes in women, were strongly associated with a greater likelihood of CRP levels of greater-than-or-equal1.0 mg/dL (p<0.001). Among persons with CRP levels of less-than-or-equal0.21 mg/dL, >0.21 to <0.5 mg/dL, 0.5 to <1.0 mg/dL and greater-than-or-equal1.0 mg/dL, the 10-year estimated risk of coronary heart disease were 13.4%, 17.6%, 19.6%, and 21.1% among men, respectively, and 2.7%, 3.6%, 4.1% and 4.3% among women, respectively (both p<0.001 across CRP categories); higher risks across CRP groups were also found among ethnic/gender subgroups. CRP remained a significant predictor of coronary heart disease risk in unadjusted and age-adjusted analyses. Conclusion. Elevation of CRP is associated with several major coronary heart disease risk factors and with unadjusted and age-adjusted projections of 10-year coronary heart disease risk in both men and women. (c)2001 CHF, Inc. Presented at the Fifth International Conference on Preventive Cardiology, Osaka, Japan, May, 2001.

Journal Article↗
PubMed2000

Phosphate immobilization using an acidic type F fly ash.

Batch equilibration experiments using a low calcium ( approximately 1 wt.% as CaO), acidic (pH approximately 4.5) Type F fly ash demonstrated phosphate immobilization on the order of 100% to 75% for 50 and 100 mg P/l solutions, respectively. A loosely compacted column of fly ash similarly removed 10 mg P/l for over 85 pore volumes. While the interactions between phosphate and calcium-rich (Type C) ashes are relatively well understood, insight into the mechanisms of phosphate immobilization in Type F ash necessitated a review of the phosphate chemistry and interactions with acidic geomedia. Phosphate adsorption was subsequently modeled using a constant capacitance model approach (CCM) excluding precipitation reactions. Our CCM predictions of total phosphate immobilization (20%) were substantially less than the results of the batch equilibration experiments and phosphate adsorption predicted by other researchers examining near pure natural and synthetic geomedia due to the compositional heterogeneity of the fly ash. Nevertheless, for the amorphous and crystalline phases studied, the immobilization of phosphate in the Type F fly ash is attributed to the formation of insoluble aluminum and iron phosphates at low to medium values of pH.

Adsorption↗
PubMed1994

Separation and characterization of the main methylated nucleobases from nuclear, cytoplasmic and poly (A)+ RNA by high-performance liquid chromatography and mass spectrometry.

We were able to detect nine methylated nucleobases (3-methyluracil, 1-, 2-, 3- and 7-methylguanine, 1-, 2-, 3- and 6-methyladenine) in RNA from rat and calf liver, baker's yeast, Torula and Euglena cells by using reversed-phase high-performance liquid chromatography and thermospray mass spectrometry. Total cellular, nuclear, cytoplasmic and poly (A)+ RNA from rat liver showed marked methylation, mainly of 1- and 3- methylguanine, and 3- and 2-methyladenine. These bases were especially abundant in nuclear RNA and, to a lesser extent, in poly (A)+ RNA. In contrast, 7-methylguanine and 6-methyladenine were poorly represented in poly (A)+ RNA.

Animals↗
PubMed1994

Chemical mutagenesis testing in Drosophila. IX. Results of 50 coded compounds tested for the National Toxicology Program.

Fifty chemicals were tested for mutagenic activity in post-meiotic and meiotic germ cells of male Drosophila melanogaster using the sex-linked recessive lethal (SLRL) assay. As in the previous studies in this series, feeding was chosen as the first route of administration. If the compound failed to induce mutations by this route, injection exposure was used. One gaseous chemical (1,3-butadiene) was tested only by inhalation. Those chemicals that were mutagenic in the sex-linked recessive lethal assay were further tested for the ability to induce reciprocal translocations. Eleven of the 50 chemicals tested were mutagenic in the SLRL assay. These included bis(2-chloroethyl) ether, 1,4-butanediol diglycidyl ether, 1-chloro-2-propanol, dimethyl methylphosphonate, dimethyl morpholinophosphoramidate, dimethyloldihydroxyethylene urea, 2,2-dimethyl vinyl chloride, hexamethylphosphoramide, isatin-5-sulfonic acid (Na salt), isopropyl glycidyl ether, and urethane. Five of these, including 1,4-butanediol diglycidyl ether, 2,2-dimethyl vinyl chloride, hexamethylphosphoramide, isopropyl glycidyl ether, and urethane, also induced reciprocal translocations.

Animals↗
PubMed1994

Chemical mutagenesis testing in Drosophila. X. Results of 70 coded chemicals tested for the National Toxicology Program.

Seventy chemicals were tested for the ability to induce sex-linked recessive lethal (SLRL) mutations in postmeiotic and meiotic germ cells of male Drosophila melanogaster. As in the previous studies in this series, adult feeding was chosen as the first route of administration. If the compound failed to induce mutations by this route, injection exposure was used. Two chemicals, n-butane and propylene, were gaseous and therefore tested only by inhalation. One chemical (dimethylcarbamoyl chloride) was tested only by injection. Those chemicals that were mutagenic in the SLRL assay were further tested for the ability to induce reciprocal translocations. Sixteen of the 70 chemicals tested were mutagenic in the SLRL assay: 3-chloro-2-methylpropene, 3-(chloromethyl)pyridine HCl, dimethylcarbamoyl chloride, HC blue 1,3-iodo-1,2-propanediol, malaoxon, N,N'-methylene-bis-acrylamide, 4,4'-methylenedianiline 2HCl, ziram, cis-dichlorodiaminoplatinum II, 1,2-dibromoethane, dibromomannitol, 1,2-epoxypropane, glycidol, myleran, and toluene diisocyanate. The last seven also induced reciprocal translocations. A comparison of the results from the SLRL assay with other assays for mutagens and carcinogens suggests that the SLRL assay is highly specific, but poorly sensitive, both for mutagens and potential carcinogens.

Animals↗
PubMed1992

Modifications of hepatic alpha-1-acid glycoprotein and albumin gene expression in rats treated with phenobarbital.

The serum level of alpha 1-acid glycoprotein (alpha 1-AGP) is significantly increased in various animal species by treatment with cytokines, glucocorticoids and phenobarbital. The mechanisms responsible for the cytokine-induced and glucocorticoid-induced increases are now well documented, but not so in the case of phenobarbital. The main purpose of this study was to assess whether phenobarbital acts on alpha 1-AGP synthesis in the liver at the transcriptional or translational level. Male Dark Agouti rats received 70 mg phenobarbital/kg daily for 7 days. The analysis of total hepatic RNA showed that a single injection of phenobarbital induced an 11-fold increase in phenobarbital-dependent cytochrome P450IIB mRNA, whereas seven injections of phenobarbital were required to induce a maximum 5.5-fold increase in alpha 1-AGP mRNA. Concurrently, the transcription rate of the alpha 1-AGP gene rose 3.5-fold. Hepatocytes isolated after the seventh injection of phenobarbital showed a threefold increased capacity to secrete alpha 1-AGP, corresponding to a 3.2-fold increased alpha 1-AGP mRNA content in the liver. In conditions in which its effect on the induction of alpha 1-AGP synthesis was maximum, phenobarbital caused a 30% reduction in liver albumin mRNA and in albumin secretion by isolated hepatocytes, resulting from a 60-70% reduction in the rate of transcription of the albumin gene measured in isolated nuclei. We conclude that the effect of phenobarbital on alpha 1-AGP and albumin gene expression occurs at the transcriptional rather than the translational level.

Albumins↗
PubMed1992

Chemical mutagenesis testing in Drosophila: VIII. Reexamination of equivocal results.

Twelve percent of the chemicals tested for mutagenicity by the National Toxicology Program (NTP) using the Drosophila sex-linked recessive lethal assay have been classified as producing equivocal results. We have reexamined the published data and the criteria used to determine mutagenicity in light of the historical distribution of the concurrent negative controls for this project. Many of the chemicals that originally produced equivocal results have been retested under code. As a result of changes to incorporate a comparison with the historical control in the algorithm used to determine mutagenicity and as a result of new data accumulated, 4 of the 25 chemicals that gave equivocal results are judged to be mutagenic, and 11 others are judged to be nonmutagenic under our test conditions.

Algorithms↗
PubMed1992

Genetic toxicology of acrylic acid.

Acrylic acid was tested for gene mutations in the in vitro CHO/HGPRT assay, for chromosome aberrations in CHO cells in culture, and for potential to induce unscheduled DNA synthesis in rat hepatocytes in culture. In vivo assays performed included the Drosophila sex-linked recessive lethal assay by both the feeding and injection routes, the in vivo cytogenetic assay in rat bone marrow cells after both a 1-day and 5-day oral dosing regimen, and a dominant lethal assay in mice by both an acute and 5-day dosing regimen. All results were negative (non-mutagenic) except for the in vitro chromosome aberration assay. This latter result is consistent with the previously reported possible clastogenic activity suggested by the results of the mouse lymphoma L5178Y TK locus assay in which a predominance of small-colony mutants was observed (Moore et al., Environmental and Molecular Mutagenesis 1988, 11, 49-63). The rapid clearance of acrylic acid in animals and the weight of evidence of genetic toxicity testing, including negative in vivo data in both somatic and germ cells, indicate a lack of genetic toxicity of acrylic acid in vivo.

Acrylates↗
PubMed1991

Amplification of ribosomal DNA in the nucleolus of vitamin B12-deficient Euglena cells.

In the nucleoli of vitamin B12-deprived Euglena cells there is a 10-fold amplification of rDNA which correlates with increased numbers of fibrillar centers in the hypertrophic nucleoli. This rDNA amplification was demonstrated by means of molecular hybridization using a specific cytoplasmic rRNA probe. Most of the amplified sequences appear as extrachromosomal copies which were observed without digestion of total cellular or nuclear Euglena DNA. Five different hybridizing sequences, three of high molecular weight and two of 19.0 and 11.5 kb, were identified. The rDNA repeat unit which contains the 11.5-kb transcriptible sequence is 19.0 kb in length and was always more abundant in the undigested total cellular DNA. The possible mechanisms involved in the induction of rDNA amplification in vitamin B12-deficient cells are discussed.

Animals↗
PubMed1990

Interleukin 1 beta modulates hepatic synthesis of alpha 1-acid glycoprotein in the fetal rat.

The ability of the fetal rat to respond to interleukin 1 beta (IL1 beta) by expressing alpha 1-acid glycoprotein (AGP) was investigated. Eight and 20 h after injection of 7 ng IL1 beta into 19-day fetuses, liver AGP mRNA increased by a factor of 66 and 82 respectively, while serum AGP levels increased by a factor of 3 and 5. Similar treatment of the mothers altered in the fetuses neither AGP serum levels nor the amount of liver AGP mRNA. The induction of AGP gene expression in the fetal liver in response to IL1 beta was similar to that observed in the adult liver. These results demonstrate that at day 19 the fetal rat liver has acquired a mature acute-phase system.

Animals↗
PubMed1989

Chemical mutagenesis testing in Drosophila. VI. Interlaboratory comparison of mutagenicity tests after treatment of larvae.

Previous publications on the National Toxicology Program (NTP)-sponsored mutagenicity testing program in Drosophila dealt with evaluations of chemicals following adult treatment (feed, injection). The current paper deals with a comparison between the laboratories at Brown University (BRU) and the University of Wisconsin at Madison (UWM) regarding the response of larvae to treatment with chemicals in the sex-linked recessive lethal (SLRL) test and, where appropriate, the reciprocal translocation test as well. Dimethylnitrosamine (DMN) and dimethylbenz(a)anthracene were used first as reference mutagens. Six coded compounds were then evaluated regarding their repeatability in the two laboratories; the compounds were benzo(a)pyrene, 3-methylcholanthrene, coumarin, quinoline, formaldehyde, and 9-aminoacridine. It was concluded that at this time it would be imprudent to forgo larval treatment in cases where compounds proved negative after adult feeding. Accordingly, testing a series of 20 compounds negative after adult treatment is in progress.

9,10-Dimethyl-1,2-benzanthracene↗