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Biomedical subjects

M R Pudek

Publications and source records attributed to M R Pudek.

At least 19 recordsLinked to original sources
PubMed1991

Quantitative fluorometric screening test for fecal porphyrins.

We describe a fluorometric method for screening and quantifying porphyrins in stool. A small sample of stool is extracted with concentrated HCI and is diluted 200-fold in 3 mol/L HCI before analysis. An excitation scan is done from 350 to 450 nm, monitoring emission at 603 nm. Total porphyrin is estimated at the isosbestic point for coproporphyrin and protoporphyrin (402.5 nm). Monitoring emission at 603 nm eliminates interference from chlorophyll, obviating the need for extraction with ether. The position of the excitation peak gives some indication of the nature of the porphyrins in the stool. The acid extract can be injected directly into an HPLC system for fractionation studies. Our method correlates well with the spectrophotometric method developed by Lockwood et al. (Clin Chem 1985;31:1163-7). However, in our method, the sample is easier to process and the assay has higher sensitivity than their assay. The reference interval for porphyrin in healthy individuals by the fluorometric method is less than 300 nmol/g dry weight. We can detect as little as 1 nmol of porphyrin per gram (dry weight) of stool. Results of the method vary linearly with stool porphyrin concentrations as great as 4000 nmol/g dry weight. The within-run imprecision of the method is 3%.

Chromatography, High Pressure Liquid↗
PubMed1990

Low concentration galactose determination in plasma adapted to the Cobas-Bio.

Galactose elimination at blood concentrations lower than 2.22 mmol/L has been advocated as a measure of functional liver blood flow. We have adapted an assay employing galactose dehydrogenase (EC 1.1.1.48) to the Cobas-Bio to measure low galactose concentrations in plasma. The collection of blood in sodium fluoride/potassium oxalate anticoagulant tubes eliminated the necessity for the plasma deproteinization step required in similar, manual methods. The between run CV's for plasma samples spiked with galactose to concentrations of 0.13-0.5 mmol/L were 3.6% and 3.2%, respectively. Our automated assay was more precise and had a greater range of linearity than a manual galactose oxidase (EC 1.1.3.9) method set up in our laboratory (0.04-1.10 mmol/L as compared to 0.06-0.56 mmol/L). The total assay time was 20 min.

Fluorometry↗
PubMed1989

Digoxin-like immunoreactivity, displacement of ouabain and inhibition of Na+/K+ ATPase by four steroids known to be increased in essential hypertension.

An endogenous digoxin-like immunoreactive substance(s) (DLIS, "endoxin") may be of significance in the etiology of essential hypertension (EH). Progesterone, dehydroepiandrosterone sulphate (DHEA-S), 11-deoxycortisol and 18-hydroxy-11-deoxycorticosterone (18-OH-DOC), four steroids known to be increased in essential hypertension, were found to have digoxin-like immunoreactivity at levels 1,000 times higher than physiological concentrations. Of these steroids, progesterone and 18-OH-DOC were the most efficient in displacing 3H-ouabain from canine kidney Na+/K+ ATPase whereas progesterone and 11-deoxycortisol were the most potent inhibitors of this enzyme's activity. Although 18-OH-DOC and DHEA-S cross-reacted with digoxin-specific antibodies, their ability to inhibit Na+/K+ ATPase activity was minimal. Although it is concluded that these steroids may contribute to DLIS as isolated from hypertensive patients, it is unlikely that they would be of physiological significance in the etiology of EH unless they were to accumulate and act synergistically within vascular wall smooth muscle tissues.

Animals↗
PubMed1989

Screening tests for porphobilinogen are insensitive. The problem and its solution.

Standard screening tests for porphobilinogen (PBG) do not turn positive until the concentration of PBG exceeds 10-20 times the upper limit of normal. The authors have developed a screening procedure that uses a new ion-exchange resin to separate PBG from interfering substances in urine. On addition of Ehrlich's reagent, the color is more intense than that produced in the Watson-Schwartz test, and its spectrum more closely resembles that of pure PBG. By measuring the absorbance of this solution at 555 nm, it is possible to discriminate between urine samples with 9 mumol/L (2 mg/L) of PBG and those with no detectable PBG. The new screening test had positive results in two patients with latent acute intermittent porphyria; the Watson-Schwartz test had negative results in both cases. This procedure is easy to perform, has much greater sensitivity than the Watson-Schwartz test, and uses objective spectrophotometric data to separate positive from negative results.

Benzaldehydes↗
PubMed1989

A study into the nature and organ source of digoxin-like immunoreactive substance(s) in the perinatal period.

Digoxin-like immunoreactive substance(s) (DLIS) was isolated from sera and autopsy-derived tissue obtained from premature and full-term neonates. The highest tissue level of DLIS was in the small bowel followed by the adrenal, gallbladder and liver. Of the fluids examined, meconium had the highest level of DLIS. Preparative high performance liquid chromatography fractionation of cord blood generated at least six different fractions which not only contained DLIS material but also inhibited canine kidney Na+/K+-ATPase activity. Recovery/inhibition studies indicated that 72% of the canine kidney Na+/K+-ATPase inhibition within one fraction could be accounted for on the basis of progesterone content of the fraction.

Antibodies↗
PubMed1987

Minimizing analytical interferences from digoxin-like immunoreactive substances (DLIS) in cases of digoxin toxicity.

Recently, the value of therapeutic drug monitoring for digoxin has been called into question by the finding of endogenous digoxin-like immunoreactive substances (DLIS) in the serum of individuals, especially premature and full-term neonates, not being treated with digoxin. In some cases, values have been as high as 10 micrograms/L. Levels as high as 20 micrograms/L and 80 micrograms/g can be found in bile and meconium. Because of the magnitude of this interference, it is essential that methods be developed for measuring digoxin in the presence of DLIS. This is particularly important when such analyses are required in forensic science cases of suspected digoxin toxicity. This report outlines the high performance liquid chromatographic (HPLC) and radioimmunoassay (RIA) methods that we used in assessing the relative contribution made by digoxin, its metabolites, and DLIS to serum and tissue digoxin concentrations obtained by RIA in a forensic pediatric case of suspected digoxin toxicity.

Blood Proteins↗
PubMed1985

Beta 2-microglobulin levels in cerebrospinal fluid of children with leukemia and lymphoma.

Beta 2-microglobulin levels were determined in the cerebrospinal fluid (CSF) of 119 children (ages 1 1/2 to 18 years) with malignant conditions; 87 with acute lymphoblastic leukemia, 9 with acute myeloblastic leukemia, 15 with lymphoma, and 8 with solid tumours. A total of 491 CSF specimens and 202 serum specimens were analyzed over a 12-month period. The mean CSF beta 2-microglobulin and serum beta 2-microglobulin were 1.11 +/- 0.58 mg/L and 1.5 +/- 0.64 mg/L respectively and were not different from the mean CSF (1.20 +/- 0.45 mg/L) and serum beta 2-microglobulin levels (1.70 +/- 0.45 mg/L) found in control patients. Meningeal leukemia was diagnosed on the basis of cytology in 7 patients. No elevation of CSF beta 2-microglobulin was found in any specimen at the time of CNS disease. Eleven other patients showed a transient rise in CSF beta 2-microglobulin above the reference range (greater than 2.1 mg/L). No evidence of CNS involvement was found in any of these patients. Five of these patients had received a combination of intrathecal methotrexate and irradiation therapy within the previous 4 months. A transient rise in CSF beta 2-microglobulin (2-3-fold increase over baseline CSF levels), which did not exceed the upper limit of the reference range was seen in 5 of 7 other children receiving the above therapy. Our study fails to demonstrate the usefulness of CSF beta 2-microglobulin for the diagnosis of CNS metastases but suggests that a transient elevation of CSF beta 2-microglobulin may occur after intrathecal methotrexate and irradiation therapy.

Adolescent↗
PubMed1985

Gonadotrophin-secreting pituitary tumour: report and review.

A 34-year-old male with a pituitary adenoma was investigated and demonstrated to have hypersecretion of both gonadotrophins in the basal state. Immunocytochemical staining and electron microscopic examination were positive for tumour cells secreting FSH and LH. Presenting symptoms included visual disturbances, loss of libido, impotence, cold intolerance, frontal headaches, change in skin pigmentation and excessive weight gain. The patient denied alteration in hair distribution, had no acral features, galactorrhoea or gynaecomastia. Surgical extirpation resulted in complete amelioration of his symptoms over a three year follow-up period. Basal and stimulated pituitary function testing results returned to normal post-operatively. A review of the literature documents six other cases of pituitary tumour secreting both LH and FSH in the basal state. More commonly, the pituitary adenoma secretes FSH only. The literature is reviewed with regard to both types of tumour.

Adenoma↗
PubMed1985

Effect of assay conditions on cross reactivity of digoxin-like immunoreactive substance(s) with radioimmunoassay kits.

One or more digoxin-like immunoreactive substances (DLIS), most frequently present in serum of premature and full-term neonates. cross react to various extents with different digoxin immunoassay kit reagents. Mostly, this variation is attributed to the relative cross reactivity of DLIS with the antiserum in each kit. However, modification of standard assay procedures for digoxin can also greatly alter the relative cross reactivity of DLIS. Using sequential RIA kit methods for digoxin by 20 to 60% relative to the standard equilibrium RIA mode. Cross reactivity was decreased still more if the concentrations of antiserum (binding-site concentration) and tracer (125 l-labeled digoxin) were decreased, and conversely. Serum samples containing only digoxin, analyzed by the modified method, consistently yielded results well comparable with those obtained with the manufacturers' recommended procedures. We describe use of the different responses to digoxin and DLIS of standard and sequential radioimmunoassays and use of simultaneous equation to calculate the concentration of DLIS (in digoxin equivalents) in digoxin-containing samples.

Cross Reactions↗
PubMed1984

Artefactual decrease in total protein concentration in patients with monoclonal gammopathies: a method-dependent error.

We found total protein estimates in patients with monoclonal gammopathies to be erroneously low when using the Cobas-Bio centrifugal analyzer. This problem occurred only when a serum-water blank was used. This probably results from the precipitation of these proteins under conditions of low ionic strength resulting in high blank readings. The problem can be avoided if a serum-saline blank is used.

Blood Chemical Analysis↗
PubMed1984

Perinatal changes in a digoxin-like immunoreactive substance.

An endogenous digoxin-like immunoreactive substance(s) (DLIS) exists in the serum of premature and full term infants not receiving digoxin. We followed serum changes in DLIS concentration sequentially over the first 14 postnatal days in 24 premature neonates who did not receive digoxin in the intensive care nursery. All infants had measurable levels (greater than 0.6 ng/ml) of DLIS in their serum. There was a distinct peak in DLIS concentration in 19 of 24 infants occurring at 4 +/- 1.6 (SD) days after birth (range, 1-8 days). No peak was found in five infants. The peak serum level of DLIS obtained in the first 8 days of life was negatively correlated with gestational age and birth weight. DLIS levels in amniotic fluid remained constant from 16 to 33 weeks of gestation but rose from 33 wk to term. DLIS concentrations in umbilical artery, umbilical vein, and maternal serum at normal full term delivery suggested that DLIS was of fetal origin. DLIS and digoxin concentrations are additive when present in the same serum sample if measured by standard radioimmunoassay methods.

Aging↗