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Biomedical subjects

A Castro

Publications and source records attributed to A Castro.

At least 451 records · Page 25Linked to original sources
PubMed1983

A fluorescent immunoassay for theophylline: description and comparison to enzyme immunoassay, liquid chromatography and radioimmunoassay.

A fluorescent immunoassay for theophylline is described and comparatively evaluated with radioimmunoassay, high-performance liquid chromatography, and enzyme immunoassay. Fifty sera were collected from 43 patients of a large acute-care medical facility, many of whom were suffering from other diseases in addition to bronchial asthma or apnea of the newborn, and were receiving other medication besides theophylline. Assays of theophylline in each serum sample were performed by each of the 4 procedures. The four methods showed comparable results, although each method had at least one unexplained outlier. Nevertheless, all methods seemed suitable for routine chemistry laboratory use. Three of the techniques have been available for several years, but unexplained erroneous levels are sometimes obtained for every procedure.

Chromatography, Liquid↗
PubMed1983

The renin-angiotensin-aldosterone system in normal elderly subjects.

In order to observe alterations of the Renin-Angiotensin-Aldosterone (RAA) system in elderly individuals, 40 healthy Venezuelan mestizos (8 men, 32 women) over 60 years of age were examined. These subjects had a normal sodium and potassium diet and were living under normal conditions. Plasma Renin Activity (PRA), urinary and serum aldosterone levels were determined by radioimmunoassay after two hours of ambulation. Values obtained were compared to those of a similar control group under age 60. The study of the RAA system demonstrated a correlation between PRA, serum and urinary aldosterone, and the daily excretion of sodium, even though less significant than in younger subjects. A continuous, gradual descent in these parameters was observed to be related to the advancement of age until approximately age 60, at which time the PRA demonstrated a sudden drop which was not accompanied by a decrease in the level of aldosterone. The most significant changes occur around the sixth decade of life when these hormone levels drop suddenly and the relationship between PRA, urinary and serum aldosterone changes.

Adolescent↗
PubMed1983

The effect of age on the renin-angiotensin-aldosterone systems and other physiological variables in normal subjects.

The influence of age on the renin-angiotensin-aldosterone (RAA) system in 125 normal subjects, ages ranging from 13-90, in Valencia, Venezuela, was evaluated. The subjects selected were tested during their normal life style, on their usual sodium and potassium diet. Their RAA system was stimulated by walking for 2-3 hours. A highly significant inverse correlation was found between age and stimulated plasma renin activity (r = -0.7149, p less than 0.001), and between age and urinary aldosterone (r = 0.4837, p less than 0.001). No significant correlation between age and serum aldosterone was found. The most significant changes in levels of these hormones were found between ages 55 and 60 when renin and aldosterone values decreased markedly. This decrease accelerates with increasing age. Plasma renin presented an appreciable percentage of decrease when compared to the highest levels found in the lowest age group; plasma renin decreased 80%, while urinary aldosterone decreased only 40% between ages 80 and 90. In the over-60 groups this relationship between plasma renin activity and urinary and serum aldosterone levels showed both aldosterone values were higher than the corresponding plasma renin levels. We have no clear explanation for the "physiologicalhyperaldosteronism" found in groups over age 60. Age is an indispensible consideration in normal RAA system values. More intensive studies of over age 60 subjects are necessary.

Adolescent↗
PubMed1983

The relationship of aldosterone to mild essential hypertension.

Twenty-five carrier patients with mild essential hypertension (MEH) were studied. These were carefully selected, with an age range between 30 and 60 years (mean 44 years). A series of physical, biochemical and humoral parameters were studied. For purposes of comparison, 36 normotensive patients were studied under the same conditions. Our results showed that plasma aldosterone (PA) and urine aldosterone (UA) had higher values in essential hypertensive patients (p less than 0.05). The plasma renin activity (PRA) showed a slight decrease, although without statistical significance. In this same group the PA/pra coefficient was found to be high (p less than 0.05) which shows a loss of relationship between PRA and PA. In the essential hypertensive patients was found an equal correlation between PRA and PA with daily excretion of potassium (p less than 0.05) which was not shown in normal patients; on the other hand, in these latter cases was found a very significant correlation between the renin-aldosterone (RA) system and 24-hr. urinary sodium levels (p less than 0.001). Based on these findings, we believe that in this type of hypertension an aldosterone disturbance exists, which must be linked directly or indirectly to the disturbance of sodium regulation. The modifications produced in the RA system in this type of hypertension is similar to the modifications found in older subjects (greater than 60 years) in the RA system hormone axis. We cannot clearly explain these findings, but we believe that essential arterial hypertension accelerated a physiological process in elderly subjects (greater than 60 years).

Adult↗
PubMed1982

Demonstration of interference between dengue virus types in cultured mosquito cells using monoclonal antibody probes.

Cultured Aedes albopictus cells (clone C6/36), persistently infected (PI) with dengue virus type 1 (dengue-1) were found resistant to superinfection with dengue virus type 3 (dengue-3). This was determined by indirect immunofluorescent (IF) staining of cultures using monoclonal antibody against a dengue-3 type-specific antigen. Dengue-1 PI cultures stained with this antibody 3 days after superinfection with dengue-3 virus (m.o.i of 2) had dengue-3 antigen in 0.1 to 1.0% of the cells. Control cultures infected with dengue-3 at the same multiplicity contained dengue-3 antigen in greater than 90% of the cells. The resistance to superinfection was not interferon-mediated, and occurred within 20 h after primary infection. In cultures simultaneously infected with two dengue virus types, one virus type was excluded from replication in most cells. A small population of cells was also found (about 1%) that contained type-specific antigen of both dengue virus types.

Adsorption↗
PubMed1982

Quantitation of Candida albicans polysaccharide using an enzyme-linked immunosorbent assay.

The enzyme-linked immunosorbent assay (ELISA) for candida polysaccharide antigen in serum was developed by using double antibody sandwich technique. It was found that serum constituents substantially interfered with the assay. The interference was successfully decreased by heating serum in the presence of EDTA which precipitated interfering serum protein. In addition, candida antigen may be liberated from antibody complexes. The candida polysaccharide antigen in the supernatant was precipitated with ethanol and resuspended in the buffer containing gelatin. A maximum sensitivity of 10 ng/ml was found in the assay using this procedure. This procedure of serum treatment may have potential applications for the detection of other polysaccharide antigens in serum.

Alkaline Phosphatase↗
PubMed1982

Results by fluorescent immunoassay for phenytoin compared with those by enzyme immunoassay, liquid chromatography, and discrete analysis (Dupont aca).

We describe the Ames Fluorescent Enzyme Immunoassay procedure for the detection of phenytoin in serum, and compare the results with it with those by enzyme immunoassay(EMIT), "high-pressure" liquid chromatography, and the Dupont aca. Sera from 48 patients who were receiving phenytoin were promptly analyzed in duplicate by EMIT, frozen, then assayed within four weeks by the other three methods. Correlation was good between results by the fluorescent immunoassay and the other methods. The fluorescent immunoassay procedure is sensitive and requires a small sample volume (100 microliters). Sample reading time can be shortened from 30 to 15 s as the technician becomes more proficient, with no sacrifice of accuracy. The procedure is fast, easy to perform, specific, sensitive, and inexpensive; involves no radioactivity; and requires no temperature control. It is the current method of choice for detection of phenytoin in serum, in terms of precision and accuracy.

Chromatography, High Pressure Liquid↗
PubMed1981

Pool and synthesis of phosphoribosylpyrophosphate in rat embryo cells infected with X14 or H-1 parvovirus.

In rat embryo cell cultures infected with X14 or H-1 parvovirus the PRPP pool and the PRPP synthetase activity have been assayed. A radiometric method, prepared by Authors, based on the conversion of [6-14C) orotate to [6-14C) UMP by the mixed enzyme orotate phosphoribosyltransferase and orotidylate decarboxylase and on the separation of UMP by ascending chromatography, has been utilized. The PRPP pool and te PRPP synthetase activity appeared nearly unmodified in the cells infected with X14 or H-1 parvovirus compared to the mock-infected cells. Therefore, the lowered pyrimidine nucleotide synthesis in infected cells, shown in previous studies, may depend, rather than on the diminished PRPP pool, on the lower PRPP utilization; in fact, some inhibition by metabolites, that may be removed by added PRPP, might occur in the infected cells.

Animals↗
PubMed1981

Activity of some enzymes involved in "adenylate cycle" in rat embryo cells infected with parvoviruses (X14, H-1).

In rat embryo cell cultures infected with X14 or H-1 parvovirus and in mock-infected cell cultures the activity of some enzymes involved in purine nucleotide interconversion and in "adenylate cycle" was determined. The enzymatic activities have been assayed on 100,000 x g supernatant by spectrophotometric methods, measuring the absorbance variation in U.V. and by radiometric methods, resolving the radioactive products of reaction by TLC on PEI cellulose. The results indicated a decrease of the enzymatic activities that degrade purine nucleosides and nucleotides in infected cells compared to the controls. Some different behaviour patterns showed the enzymes involved in base salvage pathway; adenine phosphoribosyltransferase did not show a significant modification of activity, whereas hypoxanthine (guanine) phosphoribosyltransferase increased slightly in X14 virus-infected cells. The behaviour of the above mentioned enzymatic activities may be considered as a mechanism of purine nucleotide saving, coupled to an active salvage pathway for the synthesis of nucleotides required for the viral replication.

Adenine↗
PubMed1981

Prostatic-specific antigen: an immunohistologic marker for prostatic neoplasms.

Antiserum to a human prostate-specific antigen was raised in a rabbit and utilized by immunoperoxidase staining to evaluate its potential value as a diagnostic histologic marker for tumors of prostatic origin. All primary and metastatic prostatic malignancies reacted positively, whereas nonprostatic neoplasms did not stain with this procedure. This is the first immunohistochemical marker for prostate gland epithelium which does not represent prostatic acid phosphatase.

Adenocarcinoma↗
PubMed1981

[Computerized cerebral tomography in tuberous sclerosis. Study of 3 patients].

The findings on computerized axial tomography of the brain in three patients with tuberous sclerosis are reported. Numerous intracranial calcified nodules varying in size from a few millimeters to one centimeter, located preferentially below the ependyma of the lateral ventricles and determining filling defects in its lumen were found in all cases. Other calcified lesions were found in a subcortical location. One patient presented areas of low density throughout the hemispheric white matter, and another showed ventricular dilatation of the ventricles and basal cisternas. Computerized axial tomography is useful in the evaluation of patients with tuberous sclerosis because of its early demonstration of the characteristic intracranial lesions and detection of complications such as calcification of basal and cerebellar ganglia, hydrocephalus, and development of gliomas. Low density areas may correspond to foci of demyelinization. Furthermore, computerized axial tomography allows the demonstration of cerebral tuberosities in asymptomatic relatives, thus offsetting the inconveniences of pneumoencephalography.

Adult↗