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Biomedical subjects

J R Santos

Publications and source records attributed to J R Santos.

14 recordsLinked to original sources
PubMed2004

Simultaneous determination of E-2-nonenal and beta-damascenone in beer by reversed-phase liquid chromatography with UV detection.

A method for the simultaneous determination of E-2-nonenal and beta-damascenone in beer by reversed-phase liquid chromatography using UV detection is presented. The method consists of beer steam distillation, followed by an extraction/concentration step using Sep-Pak Plus C18 RP cartridges and determination by HPLC at 226 nm UV-absorption maximum. The identity of the compounds was confirmed by GC analysis with MS detection of the isolated fractions. A recovery factor of approximately 80% was obtained for beta-damascenone with a R.S.D. of 3%. E-2-Nonenal and beta-damascenone were monitored in a comparative study of fresh and either naturally and forced aged beer. The results obtained show that both compounds have a similar behaviour through an extended storage of beer and consequently can be used as good analytical markers of beer ageing. Nevertheless, the use of beta-damascenone seems to be more convenient because this compound appears in beer in higher concentrations than E-2-nonenal, thus making it easier to measure.

Aldehydes↗
PubMed2003

Determination of E-2-nonenal by high-performance liquid chromatography with UV detection assay for the evaluation of beer ageing.

The analysis of E-2-nonenal is of considerable interest for the brewery industry as this compound is claimed to be responsible for a paper/cardboard unpleasant flavour. Usually, the presence of E-2-nonenal can be noticed in aged beers at levels higher than 0.1 microg/l. In this work, an analytical method was developed to determine E-2-nonenal in beer involving steam distillation of beer followed by an extraction/concentration step using solid-phase extraction and determination of E-2-nonenal by HPLC with UV detection. Fastness and simplicity are the main advantages of the proposed method, when compared with other existing methodologies for the determination of E-2-nonenal in beer. Using the developed conditions, the interference of E-2-nonenal formed by degradation of its precursors during steam distillation is almost negligible. The presence of sulphur dioxide at legal levels does not interfere with the assay. The method was used in a comparative study of fresh and either naturally or forced aged beers. A much larger chromatographic peak was found near the peak of E-2-nonenal that correlates well with the peak of E-2-nonenal. Identification of the corresponding compound is currently under investigation, considering its future application on the evaluation of beer ageing.

Aldehydes↗
PubMed2003

Risk modeling, assessment, and management of lahar flow threat.

The 1991 eruption of Mount Pinatubo in the Philippines is considered one of the most violent and destructive volcanic activities in the 20th century. Lahar is the Indonesian term for volcanic ash, and lahar flows resulting from the massive amount of volcanic materials deposited on the mountain's slope posed continued post-eruption threats to the surrounding areas, destroying lives, homes, agricultural products, and infrastructures. Risks of lahar flows were identified immediately after the eruption, with scientific data provided by the Philippine Institute of Volcanology, the U.S. Geological Survey, and other research institutions. However, competing political, economic, and social agendas subordinated the importance of scientific information to policy making. Using systemic risk analysis and management, this article addresses the issues of multiple objectives and the effective integration of scientific techniques into the decision-making process. It provides a modeling framework for identifying, prioritizing, and evaluating policies for managing risk. The major considerations are: (1) applying a holistic approach to risk analysis through hierarchical holographic modeling, (2) applying statistical methods to gain insight into the problem of uncertainty in risk assessment, (3) using multiobjective trade-off analysis to address the issue of multiple decisionmakers and stakeholders in the decision-making process, (4) using the conditional expected value of extreme events to complement and supplement the expected value in quantifying risk, and (5) assessing the impacts of multistage decisions. Numerical examples based on ex post data are formulated to illustrate applications to various problems. The resulting framework from this study can serve as a general baseline model for assessing and managing risks of natural disasters, which the Philippines' lead agency-the National Disaster Coordinating Council (NDCC)-and other related organizations can use for their decision-making processes.

Journal Article↗
PubMed2001

Expression of results with uncertainty for the determination of pesticides in melon--experience in a proficiency test.

The expression of results with an uncertainty through the "bottom-up" approach, involving the estimation and combination of all the sources of uncertainty, represents a challenge when the analytical method includes mass transfer steps (MTS). These steps (e.g. extraction, evaporation, digestion, etc.) with inherently different from 100% recoveries lack models capable of describing their precision and efficiency. Recently, a new methodology was published aimed at the estimation of the performance of these critical steps. Comparison of the experimental dispersion from the replicated analysis of spiked samples with the combination of the uncertainty associated with gravimetric, volumetric and instrumental quantification steps (described by well established models) allows the estimation of the MTS uncertainty. Evaluation of the behaviour of the MTS within the analytical range supports the use of developed estimations over a wide concentration range. This methodology was applied, with success, to the determination of pesticide residues in melon in one particular proficiency test organised by the Food Analysis Performance Assessment Scheme (FAPAS) between November 2000 and February 2001.

Chromatography, Gas↗
PubMed2000

Estimation of precision and efficiency mass transfer steps for the determination of pesticides in vegetables aiming at the expression of results with reliable uncertainty.

A 'bottom-up' approach for the expression of results obtained from analytical methods that include analytical steps with recovery inherently different from 100% [mass transfer steps (MTS): extraction, evaporation, clean-up procedures, digestion, etc.] is presented. The estimation of the combination of all MTS uncertainty involves the comparison of the experimental dispersion of replicated analyses of spiked samples with the estimation of the uncertainty obtained for the combination of all uncertainty sources except MTS ones ('incomplete' estimation). The estimation of MTS uncertainty by difference is performed after evaluating the statistical difference between the 'incomplete' estimation and the experimental dispersion (F-test). When the two estimations are statistically equivalent, the MTS uncertainty is considered to be negligible in relation to the other sources budget. The assumption of constancy of MTS performance within the analytical range is tested through single analyses at several concentration levels and is evaluated by the inclusion of the expected values at the intervals resulting from the combination of the MTS uncertainty estimation performed at one concentration level and the 'incomplete' estimation. The developed methodology can also be useful for method optimisation and validation and for the detection of small trends in results. The determination of pesticides in sweet peppers by GC-NPD was used to explore the above concepts.

Chromatography, Gas↗
PubMed1998

Culture of human amniotic cells: a system to study interferon production.

This study investigated whether primary culture of human amniotic membrane cells (PCHAM) could be used as an in vitro model system for the study of interferon (IFN) production. PCHAM cells infected with Newcastle disease virus (NDV) produced the two antigenic types of IFN, previously shown in a amniotic membrane cells (HAM) system. PCHAM IFN was detected as early as 2 h after NDV infection and was composed by two antigenically distinct fractions, one neutralized with anti-HuIFN beta antibody and another that is not related to IFN beta, -alpha and -gamma. These fractions correspond respectively to 80 and 20 per cent of the IFN produced 4 h after virus induction, 55 and 45 per cent of the IFN produced from 4 to 12 h and 67 and 33 per cent of the IFN produced 12 h after virus induction. A cDNA library, established from PCHAM with or without NDV infection, was screened for IFN alpha and -beta using specific primers. The PCR product, amplified by IFN beta primers, was cloned, sequenced and expressed in Escherichia coli M15. The sequences of several cloned cDNAs were identical to HuIFN beta gene and the antiviral activity of the expressed protein was neutralized only by antiHuIFN-beta antibody. The other IFN fraction not neutralized by polyclonal antibodies anti-IFN beta, -alpha and -gamma is now being studied.

Amnion↗
PubMed1998

Follicular thyroid carcinoma: chromosome analysis of 19 cases.

Short-term cultures of 19 follicular thyroid carcinomas were examined cytogenetically. Clonal chromosomal changes were detected in 12 tumors. Two follicular carcinomas had only numerical alterations: one with a hyperdiploid karyotype with trisomies/polysomies of chromosomes 7 and 12, similar to the karyotypes previously identified in a sub-group of benign thyroid lesions, and the other with monosomy 20. In the remaining ten cases several structural chromosome anomalies were found. Loss of the short arm of chromosome 3 was observed in one tumor. In two widely invasive and metastasizing follicular carcinomas there was a t(7;8)(p15;q24) as the sole abnormality in one case and a der(8)t(7;8)(p15;q24) together with other cytogenetic alterations in the other case. This finding suggests that t(7;8)(p15;q24) may be related to an aggressive behavior of follicular thyroid carcinomas.

Adenocarcinoma, Follicular↗
PubMed1997

Molecular analysis of the RET proto-oncogene in patients with sporadic medullary thyroid carcinoma: a novel point mutation in the extracellular cysteine-rich domain.

Germline point mutations in the RET proto-oncogene are associated with multiple endocrine neoplasia type 2 (2A and 2B) and familial medullary thyroid carcinoma. On the other hand, somatic point mutations of RET have been described in a subset of sporadic medullary thyroid carcinomas (MTCs). We examined tumor and blood DNA of thirteen apparently sporadic MTC patients for mutations in RET exons 10, 11, 13, 15 and 16 to determine whether they had true sporadic tumors or either de novo or occult germline mutations. Three different somatic missense mutations were documented in seven patients. In five patients a mutation in exon 16, codon 918, (ATG-->ACG) causing a Met-->Thr substitution was found. In the remaining two patients the mutation affected exon 11: codon 630 in one case and codon 634 in the other. In both cases a T-->C transversion was identified causing a Cys-->Arg substitution. In conclusion, absence of a germline mutation in RET exons 10, 11, 13 or 16 is evidence against an inherited form in all cases. In seven patients, identification of a somatic mutation supported the previous clinical diagnosis of sporadic medullary thyroid carcinoma; in one of them we identified a hitherto undescribed somatic point mutation at codon 630.

Adult↗
PubMed1997

Reception of Morse code through motional, vibrotactile, and auditory stimulation.

The potential for communication through the kinesthetic aspect of the tactual sense was examined in a series of experiments employing Morse code signals. Experienced and inexperienced Morse code operators were trained to identify Morse code signals that were delivered as sequences of motional stimulation through up-down displacements (roughly 10 mm) of the fingertip. Performance on this task was compared with that obtained for both vibrotactile and acoustic presentation of Morse code using a 200-Hz tone delivered either to the fingertip through a minishaker or diotically to the two ears under headphones. For all three modalities, the ability to receive Morse code was examined as a function of presentation rate for tasks including identification of single letters, random three-letter sequences, common words, and sentences. Equivalent word-rate measures (i.e., product of percent correct scores and stimulus presentation rate) were nearly twice as high for auditory presentation as for vibrotactile stimulation, which in turn was about 1.3 times that for motional stimulation. The experienced subjects outperformed the inexperienced subjects by amounts that increased with task complexity. For example, the former were able to receive sentences at 18 words/min with motional stimulation, whereas the latter, following 75 h of training, were unable to perform this task. The present results and those of other research with tactual communication systems are compared, particularly regarding estimates of information-transfer rates.

Acoustic Stimulation↗
PubMed1994

Calcitonin-producing insulinoma: clinical, immunocytochemical and cytogenetical study.

The case of a patient with a large goitre associated with hypercalcitoninaemia and fasting hypoglycaemia is reported. Pentagastrin (PG) test was negative. Repeated measurements of fasting glycaemia, insulin and C peptide established the diagnosis of insulinoma. After localization by endoscopic ultrasonography, a distal pancreatectomy was performed and a small insulinoma was recovered. Glycaemia and calcitonin (CT) became normal. The tumour cells displayed a strong immunoreactivity for insulin and CT. Cytogenetical evaluation of the tumour revealed a translocation t(1;9) (p13;p22).

Aged↗
PubMed1991

Mucoepidermoid carcinoma of the salivary glands: a reappraisal of the influence of tumor differentiation on prognosis.

Thirty-nine cases of mucoepidermoid carcinoma of the salivary glands were reviewed for a reappraisal of the influence of the grade of differentiation on the outcome of the disease. The age of the patients ranged between 7 and 84 years. Fifteen patients were females and 24 males. The tumors were located at the parotid gland (n = 30), the submaxillary gland (n = 1), the soft palate (n = 5) and the oral mucosa NOS (n = 3). At presentation 4 tumors were intraglandular and 35 extraglandular; three patients had lymph node metastases and one patient lung metastases. The grade of differentiation was assessed using the criteria of Healey et al. Twelve tumors were classified as grade I, 17 as grade II, and 10 as grade III. Follow-up information was obtained with a duration of 5-144 months (mean 44.7 months). Six cases recurred locally and 5 developed metastases. Five years cumulative survival was 100% for grade I, 70.1% for grade II, and 47.2% for grade III. The results point to the usefulness of the assessment of the grade of differentiation as a guide to anticipate the outcome of the disease.

Actuarial Analysis↗
PubMed1985

Interference of heparin with peritoneal solute transport.

To verify the action of heparin on peritoneal transport, we selected 20 patients on acute peritoneal dialysis and performed two 2-hour cycles with 2,000 cm3 of a 1.5% solution, adding 2,000 units of heparin to the second cycle. The patients were also randomized into 2 groups: group A, adding 1.5 mg gentamycin/kg to the dialysate of cycle I (without heparin), and group B, adding the same dose of gentamycin to cycle II (with heparin). At the end of each of the two cycles blood and dialysate were drawn for urea, creatinine, glucose, proteins and gentamycin levels, using peritoneal clearances of urea and creatinine, glucose absorption and net protein loss to compare cycle I with cycle II. We found that the peritoneal transport of creatinine and urea was improved (p less than 0.02; p less than 0.05) and glucose absorption increased (p less than 0.01) with heparin, without any significant change in protein loss. Contrary to common belief, heparin in a 1,000-U/l dose improved the absorption of gentamycin from the dialysate (p less than 0.01).

Adult↗
PubMedDate not supplied

[Hydro-electrolyte changes induced by transurethral prostatic resection].

Transurethral resection prostatectomy (TURP) has been associated with severe hyponatremia due to massive absorption of bladder irrigation fluid (IF). TURP was performed in 41 patients using Sorbitol-Mannitol IF (Group A) and in 6 patients using distilled water (Group B). Six other patients were operated upon using surgical procedures identical in time and type of anesthesia to TURP (Group C). The three groups were studied with the same protocol that included blood collected before (time I), immediately after (time II) the procedure and 1 hour later (time III). Serum sodium decreased significantly in the 3 groups from time I to time II, an average of 3.4 mEq/l with Mannitol-Sorbitol, 2.3 mEq/l with distilled water, and 4.4 mEq/l in group C. Osmolality did not change significantly between the 3 times of collection and Osmolar Gap only increased from time I to II in the Sorbitol-Mannitol group. In conclusion, mild decrements in serum sodium with no clinical relevance are a common post-TURP finding, but should not be greater than in other similar general surgery without bladder irrigation. Hyposmolality did not constitute a problem.

Aged↗