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Biomedical subjects

A Prins

Publications and source records attributed to A Prins.

52 records · Page 3Linked to original sources
PubMed1992

Transferrin index: an alternative method for calculating the iron saturation of transferrin.

We surveyed 140 clinical chemistry laboratories in Australia to establish which laboratory methods they used to determine serum iron status: 125 measured serum iron (Fe), 85 measured transferrin (TRF), 47 measured total iron-binding capacity (TIBC), and 14 measured both TRF and TIBC. Of the 55 laboratories routinely reporting TRF saturation (TS), 16 calculated TS directly as (Fe/TIBC) x 100, and 9 used [Fe/(TRF x 2)] x 100. Thirty laboratories measured TRF and converted it to an equivalent TIBC concentration; the derived TIBC was then used to calculate TS. We measured iron, TIBC, and TRF concentrations in 94 control subjects, 59 patients with alcoholic liver disease (ALD), and 20 with proven genetic hemochromatosis (GH). TS was compared with a transferrin index (TI = Fe/TRF) to determine whether both methods were sensitive for GH screening and which method gave the fewest false-positive results with discrimination limits of > 55% and > 1.0, respectively. All GH patients were detected by both TS and TI at these limits. One control subject had a TI > 1.0, whereas three control subjects had a TS > 55%. Nine patients with ALD had a TI > 1.0 and 11 ALD patients had a TS > 55%. Some iron-overload patients had lower than expected TS values compared with TI, possibly because of ferritin interference in the TIBC assay. Also, the precision of the TRF assay was better than that of the TIBC assay: CVs of 1.85-3.68% vs 6.17%. We therefore recommend that calculated TI replace TS in screening for iron overload.

Australia↗
PubMed1991

Subcellular distribution and phosphorylation of vinculin isoforms in human blood platelets.

In this study we investigated human blood platelet vinculin microheterogeneity, the subcellular localization and phosphorylation of the different isoforms before and after platelet stimulation. At least 5 vinculin isoforms could be detected, as well as meta-vinculin. These isoforms did not demonstrate a specific subcellular localization, i.e. their relative content was similar in cytoskeleton, membrane skeleton and cytosol. Upon platelet stimulation with thrombin a small increase in alpha-vinculin was noted in all platelet subfractions. The cytoskeleton of non-stimulated platelets contained a minor quantity of vinculin. Upon thrombin stimulation of the platelets the cytoskeletal vinculin content increased significantly; previously we already reported a maximal 10% incorporation of the total platelet vinculin content into the cytoskeleton upon stimulation. A phosphorylation of a minor vinculin-isoform, i.e. at the alpha'/alpha location was mainly detected in the cytoskeleton. This phosphorylation was observable in the non-stimulated platelet cytoskeletal vinculin. These findings argue against a regulatory role for vinculin phosphorylation in the uptake of the main isoforms of this protein in the platelet cytoskeleton upon thrombin stimulation. The function of the phosphorylated cytoskeletal vinculin remains to be established.

Blood Platelets↗
PubMed1991

Psychophysiological responses in the diagnosis of posttraumatic stress disorder in Vietnam veterans.

In one sample of 104 male Vietnam combat veterans, we found that five heart rate parameters from a psychophysiological assessment could correctly discriminate 75% of the sample into those with PTSD and those without it. Using a stepwise approach, we found adding 10 blood pressure parameters increased discrimination to 80%, while adding five parameters from frontal electromyograms did not increase discrimination. Cross-validation of the heart rate parameters on a new sample of 96 veterans resulted in 83% correct discrimination.

Adult↗
PubMed1991

Changes in plasma norepinephrine to combat-related stimuli among Vietnam veterans with posttraumatic stress disorder.

Plasma norepinephrine samples were obtained before and after exposure to auditory stimuli reminiscent of combat from two groups of male Vietnam veterans with combat experience: one with diagnoses of PTSD (N = 15) and one with no mental disorder (N = 6). Results showed a significant 30% rise in plasma norepinephrine for the PTSD group, with no change in the comparison group.

Acoustic Stimulation↗
PubMed1991

Prediction of maximal heart rate during a submaximal work test.

A multiple regression equation was developed utilizing submaximal ratings of perceived exertion and heart rate collected during a treadmill walking test to predict maximal heart rate (MHR). One hundred subjects were administered a modification of the Balke Treadmill test during which time submaximal ratings of perceived exertion (Borg Scale) and heart rate measurements were recorded. Subjects worked until volitional fatigue and maximal heart was recorded. A multiple regression equation was developed which did not require the subject to work at greater than 85% of MHR. The multiple regression equation is MHR = 108.461 + 0.5108 (RPE 15)-0.6570 (8HR) + 0.6075 (10HR)-0.2641 (age in years) with RPE 15 equal to the heart rate at a perceived exertion rating of 15 on the Borg Scale, 8HR equal to the heart rate at 8 minutes and 10HR equal to the heart rate at 10 minutes. It was found that the regression equation significantly improved the ability to predict MHR and represented a 28% improvement in the commonly used equation MHR = 220-age.

Adult↗
PubMed1989

Synthesis of platelet-activating factor by human blood platelets and leucocytes. Evidence against selective utilization of cellular ether-linked phospholipids.

Synthesis of platelet activating factor (PAF) in blood platelet suspensions may be due to leucocyte contamination. We therefore investigated PAF synthesis in human blood platelet suspensions and granulocyte- (PMN)-enriched leucocyte suspensions upon stimulation by thrombin and Ca2+-ionophore A23187, both in the presence and absence of the presumed PAF catabolism inhibitor phenylmethylsulfonyl fluoride (PMSF). PAF synthesis was measured by aggregation of washed rabbit platelets and by [3H]acetate incorporation. In contrast to A23187, thrombin was unable to stimulate PAF synthesis by leucocytes. As thrombin did induce PAF synthesis by platelet suspensions, this was evidently not due to leucocyte contamination. A23187 also induced PAF synthesis by platelets, but this was dependent upon the platelet isolation method and possibly associated activation. The ratio of [3H]acetate incorporation into 1-alkyl- versus 1-acyl-2-acetylglycerophosphocholine upon stimulation of non-PMSF-treated leucocytes and platelets amounted to 12.8 and 1.2, respectively. These values are at least 10-fold higher than the ratio of 1-alkyl versus 1-acyl species in the cellular phosphatidylcholine precursor for PAF. By PMSF pretreatment, the distribution of incorporated [3H]acetate between 1-ether- and 1-ester-linked species became similar to that in the precursor phosphatidylcholines of the respective cell type, due to increased recovery of [3H]acetate in the acyl compounds. Both leucocyte and platelet homogenates rapidly degraded acylacetylglycerophosphocholine to (acetyl)glycerophosphocholine, and this deacylation was inhibited by PMSF pretreatment of the cells. We conclude that upon cell stimulation a phospholipase A2 converts both alkylacylglycerophosphocholine and diacylglycerophosphocholine to the 2-lysoanalogs in a ratio similar to the occurrence of the parent compounds. The acetyltransferase subsequently acetylates both compounds to acylacetylglycerophosphocholine and alkylacetylglycerophosphocholine (PAF), respectively. Deacylation of the 1-ester-linked species, either before or after acetylation, gives the impression of selective utilization of 1-ether-linked species for PAF production. It is only after inhibition of the deacylation by pretreatment of the cells with PMSF that a mainly nondiscriminative use of 1-ether- and 1-ester-linked species by both phospholipase A2 and acetyltransferase becomes evident.

Acetates↗
PubMed1987

Age-related deficiency of the synthesis of platelet activating factor by leukocytes from Zellweger patients.

Ca2+-ionophore A23187-induced synthesis of the alkoxyether lipid platelet activating factor (PAF) by leukocytes from Zellweger patients was undetectable in two patients studied at 3 and 4 weeks of age, reduced in a third patient studied at 2 months of age, and in the low normal range in four patients studied between 4 months and 5 years of age. We have previously reported that plasmalogen-type phosphatidylethanolamine (PE) levels of erythrocytes are reduced in Zellweger patients up to 20 weeks of age, but normal in older patients. These levels were reduced in the three patients with abnormal PAF synthesis, and normal in the other four patients. The results suggest a close relationship between the age of the patients at sampling, and both the A23187-induced capacity of leukocytes to synthesize PAF and the plasmalogen PE levels in their erythrocytes.

Abnormalities, Multiple↗
PubMed1984

Atypical alkaline phosphatase isoenzyme in serum from a patient with Hodgkin's disease.

An alkaline phosphatase isoenzyme that did not move from the origin in agarose gel electrophoresis was detected in serum from a 51-year-old woman with Hodgkin's disease. Inhibitor and heat-inactivation studies of the patient's serum alkaline phosphatase showed properties resembling those of both liver and bone isoenzymes. No immunoglobulin or high-molecular-mass complexes with the alkaline phosphatase isoenzyme were detected. The relative molecular mass (Mr) of the atypical alkaline phosphatase isoenzyme was 182 000, that of the liver alkaline phosphatase isoenzyme control 170 000. Treatment of both of these isoenzymes with neuraminidase gave a product with an Mr of 140 000. We propose that a post-translational modification increased the carbohydrate content of the liver alkaline phosphatase isoenzyme, thus changing the charge characteristics of the enzyme and decreasing its electrophoretic mobility. We believe this to be the first report of a post-translational modification in a heat-sensitive isoenzyme of alkaline phosphatase.

Alkaline Phosphatase↗
PubMed1984

Automated amidolytic method for determining heparin, a heparinoid, and a low-Mr heparin fragment, based on their anti-Xa activity.

Using the chromogenic substrate S-2222, we have optimized and automated an amidolytic assay for heparin. The assay is based on the detection of anti-Xa activity generated by heparin in plasma. The method is reproducible (intra- and interassay CVs of 2.4 and 3.3%, respectively) and reliable in antithrombin III-deficient plasma. Results of this assay, obtained for plasma samples from patients and volunteers treated with heparin, correlate well (r = 0.899) with those of the test for activated partial thromboplastin time. Upon administration of a low-Mr heparinoid (Org 10172) and heparin fragment ( Kabi 2165), however, the activated partial thromboplastin time failed to detect anticoagulant activity, whereas the chromogenic heparin assay revealed anti-Xa activity. This automated amidolytic assay for heparin is therefore suitable not only for monitoring standard therapy with heparin but also for measuring the activity of recently developed heparin fractions.

Adult↗
PubMed1983

Comparison of auditory and visual feedback for EMG training.

27 undergraduate students participated in an experiment on EMG biofeedback. Three groups were employed (visual feedback, audio biofeedback, and control) to determine which group learned to reduce frontalis muscle tension more quickly. All subjects were trained during a 30-min. period for five days. The time consisted of a 10-min. baseline and a 20-min. biofeedback session. Over a 5-day period relaxation in the forehead due to biofeedback improved significantly. More training time yielded an increased relaxation in this area, and most learning occurred during the first two days. The significant interaction of training and time illustrated that the two biofeedback groups produced a more pronounced relaxation in the forehead muscle than did the control group. No significant difference was found between the two biofeedback groups.

Adolescent↗
PubMed1982

H-Pro-[3H]Leu-Gly-NH2: plasma profile and brain uptake following subcutaneous injection in the rat.

Following subcutaneous injection of the tripeptide H-Pro-[3H]Leu-Gly-NH2 ([3H]PLG) in rats, the profile of intact peptide and its radioactively labeled metabolites was examined both in plasma and in brain tissue. [3H]PLG and metabolites were determined in trichloroacetic acid extracts by reverse-phase paired-ion HPLC. Maximal plasma levels of unmetabolized PLG were reached 6-8 min after administration, after which they decreased with an elimination half-life of 20 min. The uptake of [3H]PLG in the brain ranged from 0.0013% to 0.0017% of the administered dose per g tissue at 6-30 min following subcutaneous injection. After comparing these results with our previous findings with intravenous injection of [3H]PLG, it seemed likely that the subcutaneous route of administration might be more effective in eliciting CNS effects of PLG than the intravenous route of administration. The metabolite profiles in plasma and brain point to an initial cleavage of PLG at the NH2-terminal side and a very rapid degradation of the peptide intermediate H-Leu-Gly-NH2.

Animals↗
PubMedDate not supplied

Effectiveness of a single and a repeated screen for hearing loss in the elderly.

The aim of this study was to assess the value of repeated audiometric screens offered to elderly in general practice. In 1991, an audiometric screen was performed on 660 participants, aged 60 years and over, enlisted in one general practice near Rotterdam, the Netherlands. We repeated the audiometric screen 5 years later in 80.2% (405/505) of the eligible participants of the first screen. After the first screen, 24.3% of those who were hearing impaired had discussed this with their general practitioner, 21.5% were referred to a specialist in otolaryngology and 12.1% had been prescribed a hearing aid. The effect of the repeated screen was lower as only 7.3% of the hearing impaired participants received a hearing aid. Efforts to screen on hearing loss will be fruitless and can best be avoided by general practitioners unless strategies are developed to increase the use of hearing aids after a positive screening result.

Aged↗
PubMedDate not supplied

Withdrawing long-term diuretic therapy in the elderly: a study in general practice in The Netherlands.

BACKGROUND: About 20% of all men and women age 65 or older are on maintenance therapy with diuretics. Multiple drug use and side effects increase with age whereas a clear indication for long-term diuretic therapy is not always present. The aim of the present study was to assess whether in some patients long-term diuretic therapy could be withdrawn in general practice. METHODS: This study is a pilot-study for a large multicentered randomized controlled trial in general practice. In one general practice in The Netherlands, 15 diuretic-using patients were selected from a total population of 52. All had been using diuretics for more than six months, were not hypertensive, and did not show overt symptoms of heart failure. In these 15 patients, diuretic medication was withdrawn under careful medical monitoring conditions. RESULTS: After six months, six patients were still without diuretic therapy. Diuretic therapy had to be resumed in nine cases, because of congestive heart failure (one), hypertension (three), bronchial asthma (one), increased ankle edema (two) and subjective complaints (two). The withdrawal of diuretic therapy caused an increase in mean systolic blood pressure, heart failure score, body weight and ankle edema. CONCLUSIONS: Long-term maintenance diuretic therapy in patients age 65 or older in general practice may be successfully withdrawn in selected cases. Careful medical surveillance during and after withdrawal is warranted.

Aged↗