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Biomedical subjects

I Vermes

Publications and source records attributed to I Vermes.

At least 73 records · Page 4Linked to original sources
PubMed1995

A novel assay for apoptosis. Flow cytometric detection of phosphatidylserine expression on early apoptotic cells using fluorescein labelled Annexin V.

In the early stages of apoptosis changes occur at the cell surface, which until now have remained difficult to recognize. One of these plasma membrane alterations is the translocation of phosphatidylserine (PS) from the inner side of the plasma membrane to the outer layer, by which PS becomes exposed at the external surface of the cell. Annexin V is a Ca2+ dependent phospholipid-binding protein with high affinity for PS. Hence this protein can be used as a sensitive probe for PS exposure upon the cell membrane. Translocation of PS to the external cell surface is not unique to apoptosis, but occurs also during cell necrosis. The difference between these two forms of cell death is that during the initial stages of apoptosis the cell membrane remains intact, while at the very moment that necrosis occurs the cell membrane looses its integrity and becomes leaky. Therefore the measurement of Annexin V binding to the cell surface as indicative for apoptosis has to be performed in conjunction with a dye exclusion test to establish integrity of the cell membrane. This paper describes the results of such an assay, as obtained in cultured HSB-2 cells, rendered apoptotic by irradiation and in human lymphocytes, following dexamethasone treatment. Untreated and treated cells were evaluated for apoptosis by light microscopy, by measuring the amount of hypo-diploid cells using of DNA flow cytometry (FCM) and by DNA electrophoresis to establish whether or not DNA fragmentation had occurred. Annexin V binding was assessed using bivariate FCM, and cell staining was evaluated with fluorescein isothiocyanate (FITC)-labelled Annexin V (green fluorescence), simultaneously with dye exclusion of propidium iodide (PI) (negative for red fluorescence). The test described, discriminates intact cells (FITC-/PI-), apoptotic cells (FITC+/PI-) and necrotic cells (FITC+/PI+). In comparison with existing traditional tests the Annexin V assay is sensitive and easy to perform. The Annexin V assay offers the possibility of detecting early phases of apoptosis before the loss of cell membrane integrity and permits measurements of the kinetics of apoptotic death in relation to the cell cycle. More extensive FCM will allow discrimination between different cell subpopulations, that may or may not be involved in the apoptotic process.

Annexin A5↗
PubMed1995

Dissociation of plasma adrenocorticotropin and cortisol levels in critically ill patients: possible role of endothelin and atrial natriuretic hormone.

The regulatory mechanisms of the hypothalamo-pituitary-adrenal system were studied in critically ill, intensive care unit patients. Serial measurements of immunoreactive ACTH-(1-39) (ACTHi), cortisol, endothelin-1 (ETi), and atrial natriuretic hormone (ANHi) were performed in blood samples of 18 patients with clinically defined sepsis, 12 critically ill patients after multiple trauma, and 15 hospitalized matched control subjects without acute illness for 8 consecutive days after admission. On admission, plasma levels of cortisol and ACTHi were significantly elevated in patients with sepsis (1.32 +/- 0.21 mumol/L and 130.0 +/- 38.2 pmol/L, mean +/- SD) and with multiple trauma (1.23 +/- 0.28 mumol/L and 123.7 +/- 41.3 pmol/L) compared to those in the control subjects (0.37 +/- 0.08 mumol/L and 15.6 +/- 5.8 pmol/L, respectively). The plasma cortisol levels of critically ill patients remained high (> 0.8 mumol/L) during the whole observation period. In contrast, plasma ACTHi levels decreased between days 3-5, reaching significantly lower levels on day 5 compared to those in the control group and remained below 5.0 pmol/L during the rest of the observation period. Plasma levels of ETi and ANHi were significantly elevated during the whole period in both patient groups (ETi, > 10 ng/L; ANHi, > 250 ng/L) compared to those in control subjects (< 5 and < 50 ng/L, respectively). The high plasma concentration of ETi observed in our patients may stimulate the steroid secretion of the adrenal cortex directly or potentiate the adrenal effect of ACTH. On the other hand, the increased concentration of ANHi found in critically ill patients together with the increased plasma cortisol level may explain the inhibition of ACTH secretion. Accordingly, we speculate that the high ET level exerts a positive drive on the adrenocortical level, that the high ANH level has an inhibitory effect on the hypothalamo-pituitary level, and that both mechanisms play a role in regulation of the hypothalamo-pituitary-adrenal axis during critical illness.

Adrenocorticotropic Hormone↗
PubMed1993

Similar alterations of lymphocyte subpopulations in type I and type II diabetes.

Peripheral blood lymphocytes of diabetes mellitus patients were analyzed by flow-cytometry using monoclonal antibodies directed against cell surface markers present in T- and B-cells, monocytes and natural killer cells. The lymphocyte subsets were quantified and expressed in an absolute amount. The study included 17 patients with type I (insulin-dependent), 21 patients with type II (non-insulin-dependent) diabetes and 40 age-matched control subjects. Quantification of the cells present within different lymphocyte subsets revealed a general increase in both patient groups compared to their controls, with the exception of activated T-cells. However, no significant difference was found in the relative amount of T-helper cells and T-suppressor/cytotoxic cells of the diabetes patients when they were compared with their control groups. The fact that we found similar changes in lymphocyte subsets in both type I and type II diabetes suggests that the altered immunological state is secondary to the diabetes mellitus in general.

Adolescent↗
PubMed1992

Influence of biological variations and sample handling on measured microalbuminuria in diabetic patients.

Five immunochemical assays for determining low concentrations of albumin were investigated. These were a radioimmunoassay (RIA); turbidimetric immunoassays (TIA) both according to end-point measuring principle on a Cobas Fara and Hitachi 717 analysers, and according to kinetic measuring principle on a Turbitimer instrument; and a nephelometric immunoassay (NIA). All achieved the analytical goal necessary for optimal patient care. The correlations between the albumin concentrations measured with the different techniques were very good. In vitro glycation of albumin did not influence albumin concentrations measured by the five assays. Urine albumin excretion measured over 3 consecutive days showed considerable day-to-day variation. This was highest for spot-urine specimens and significantly lower for 24 h and timed-overnight samples. Variation of storage temperature (room temperature, 4 degrees C, -20 degrees C), time (up till 3 months), and pH (within the range pH 5-8) of the urine samples did not change significantly the measured albumin concentrations. Different sample preparations (vortex-mixing, centrifugation, and thawing) had no influence on the measured albumin concentration. In conclusion, a maximum standardization of the collection of timed-overnight urine samples for screening and 24 h urine samples for confirmation of microalbuminuria during 3 consecutive days is more crucial than the choice of the immunological technique.

Albumins↗
PubMed1992

Micral-Test: a qualitative dipstick test for micro-albuminuria.

Micro-albuminuria is a very sensitive predictor of the development of renal disease in insulin- and non-insulin-dependent diabetes mellitus. A reliable dipstick test for routine screening for micro-albuminuria is, therefore, desirable. Such a test has been developed by Boehringer Mannheim, Germany, and marketed as Micral-Test. It is an immunological slide-test with semi-quantitative properties. To evaluate its performance as a screening test we compared it with a turbidimetric immuno-assay. In 396 urine specimens from 132 patients, sensitivity was 91% and specificity 96% for a discriminating albumin level of 20 mg/l. Correlation with quantitative values was reasonable (r = 0.73). We also tested for micro-albuminuria, defined as mean albumin excretion rate of > or = 20 micrograms/min, determined with the turbidimetric immuno-assay in timed overnight urines on three consecutive days, whereas Micral-Test was considered to be positive for micro-albuminuria if the albumin concentration in one of the three urine samples was > or = 20 mg/ml. In 132 patients, the sensitivity of Micral-Test was 82% and the specificity 86%. Albumin excretion rate in all false-negative results was < 50 micrograms/min. We therefore concluded that Micral-Test is a useful qualitative screening test for micro-albuminuria in diabetic patients.

Albuminuria↗
PubMed1992

Temperature effects on free-thyroxine measurements: analytical and clinical consequences.

We compared the analytical and clinical performance of two free-thyroxine (FT4) assays--a solid-phase radioimmunoassay, Spectria, and a time-resolved fluoroimmunoassay, Delfia, both of them two-step methods--with the performance of a direct radioimmunoassay, Nichols, to measure FT4 concentration in equilibrium dialysate of undiluted serum. The three assays showed comparable analytical performance. We tested clinical utility in sera from 135 healthy subjects with and without thyroxine-binding abnormalities and in 61 patients with and without thyroidal illnesses. We found significant differences for FT4 measured by different assays in sera from the same euthyroid patients. To explain the differences, we studied the influence of temperature on performance and calibration. Most important was the neglected fact that the association constant for the binding of thyroxine to thyroxine-binding globulin decreases when the temperature rises from 20 to 37 degrees C, causing a doubling of FT4. The two-step assays, if performed at room temperature without a well-defined calibration, can give misleading FT4 concentrations. This is the case when sera from patients with thyroxine-binding abnormalities are measured against kit standards, made up in normal human sera. If an assay is to reflect the in vivo FT4 concentration at body temperature in all types of samples, it should be performed at body temperature. For practical reasons 37 degrees C is recommended, and reference values should be defined at 37 degrees C. The same might be valid for other free-hormone assays.

Female↗
PubMed1991

Interpretations of five monoclonal immunoassays of lutropin and follitropin: effects of normalization with WHO standard.

Five mono(oligo)clonal immunometric assays for lutropin (LH) and follitropin (FSH)--bioMérieux, IRE-Medgenix, Serono Diagnostics, Diagnostics Products Corp. (DPC), and LKB--were evaluated in comparison with two polyclonal RIAs (DPC and Amersham). Detection limits varied from 0.04 to 0.32 int. unit/L and 0.06 to 0.86 int. unit/L for LH and FSH, respectively. Intra- and interassay precision (CV) at three concentrations varied from 2.0% to 29.8%, showing that not all kits tested gave acceptable results, especially for LH. Linearity and parallelism were acceptable, except for the DPC FSH kit and the bioMérieux LH kit. High-dose "hook" effects were seen in some kits at LH concentrations of 250 int. units/L, but not in the FSH kits up to concentrations of 350 int. units/L. Reagents in some kits cross-reacted with choriogonadotropin. The clinical validity of the assays was tested in 25 pre- and 25 postmenopausal healthy women and in 66 patients with polycystic ovary disease. In contrast to FSH, LH values varied significantly not only between polyclonal and monoclonal assays but also between the various monoclonal assays, despite the fact that all manufacturers state that their kits are calibrated on the same standards: WHO International Reference Preparation (IRP) 68/40 for LH and 78/549 for FSH. We normalized the results by using new WHO standards: IRP 80/552 for LH and IRP 83/575 for FSH. This decreased significantly the between-kit differences in LH results for individuals. The much-used LH/FSH ratio greater than 3 for diagnosing patients with polycystic ovary disease is not valid when monoclonal assays are used, and is kit-dependent. However, using the normalized results yields a "new" LH/FSH ratio, which is kit-independent and differs significantly between patients and healthy subjects.

Adolescent↗
PubMed1989

The role of serum fructosamine as a screening test for gestational diabetes mellitus.

The serum fructosamine concentration indicates the degree of glycation of serum proteins, particularly albumin, and reflects an average blood glucose level over the previous 1-3 weeks. Serum fructosamine, glycated haemoglobin (HbA1c), total serum protein, serum albumin, fasting plasma glucose and oral glucose tolerance test (OGTT) have been measured in 127 healthy control subjects, 102 type 1 and 152 type 2 diabetes mellitus patients and 106 nondiabetic pregnant women. Fructosamine concentration of 2.24 +/- 0.16 and 3.21 +/- 0.41 mmol/l (mean +/- S.D.) has been found in control subjects and diabetics respectively (P less than 0.001). During the second trimester a significantly lower fructosamine level (1.92 +/- 0.21 mmol/l) has been found in pregnant women, most likely due to the low serum albumin concentration (31.35 +/- 3.97 g/l). None of them had a fructosamine level above the normal limit of 2.55 mmol/l. On the other hand, 12 pregnant women showed a disturbed OGTT with normal fructosamine. If the serum fructosamine concentration was adjusted for 40 g/l albumin, then a mean fructosamine of 2.16 +/- 0.24 mmol/l was found in patients with gestational diabetes. Our results show that serum fructosamine has a similar diagnostic value as HbA1c for non-pregnant adults, but neither can replace OGTT for the diagnosis of gestational diabetes.

Adolescent↗
PubMed1989

Analytical and clinical evaluation of three sensitive thyrotropin assays.

Three sensitive assays (Behring, Organon and LKB-Pharmacia) for measurement of serum thyrotropin (TSH) were evaluated. All three assays showed good precision, sensitivity, linearity and for practical purposes negligible high dose hook effects. The correlations between the assays were excellent, but due to standardisation and/or matrix effects there were incomplete recoveries in two kits and the kits showed systematic differences of up to 20% in the TSH values obtained. The clinical utility of the three assays was investigated in patients with thyroidal and non-thyroidal illnesses and in healthy subjects with thyroxine binding abnormalities. According to the results of the analytical and clinical evaluation, all three kits are acceptable and reliable as first-line thyroid function tests.

Evaluation Studies as Topic↗
PubMed1988

Altered leukocyte rheology in patients with chronic cerebrovascular disease.

Erythrocyte and leukocyte suspensions were prepared from 28 patients with chronic cerebrovascular disease and 30 age- and concomitant disease-matched control subjects. Cell filterability was studied with the new St. George's filtrometer, which can discriminate between initial filtration rate as an erythrocyte parameter and filter clogging as a leukocyte parameter. Compared with control subjects, a significant increase of filter clogging was found in the patients, suggesting decreased deformability or increased adhesiveness of leukocytes or both in chronic cerebrovascular disease.

Aged↗
PubMed1987

Rheological properties of white blood cells are changed in diabetic patients with microvascular complications.

Erythrocyte and white blood cell suspensions were prepared from 22 Type 1 (insulin-dependent) and 37 Type 2 (non-insulin-dependent) diabetic patients and from 57 control subjects. Cell filterability was studied with the new "St. George's Filtrometer", which can discriminate between cell deformability and filter occlusion. A pronounced increase of filter clogging was found in diabetic patients compared with control subjects. There was no significant difference between Type 1 and Type 2 diabetic patients, but a significantly increased clogging was found in patients with retinopathy compared with retinopathy-free patients. Considering that filter occlusion is mainly due to leucocytes, our results show a reduced filterability of white blood cells in diabetic patients. Altered white blood cell function may act as an additional factor in the impairment of microvascular circulation in diabetic patients.

Adolescent↗