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Biomedical subjects

M M Müller

Publications and source records attributed to M M Müller.

At least 109 records · Page 6Linked to original sources
PubMed1991

Biocompatibility of aldehyde-fixed bovine pericardium. An in vitro and in vivo approach toward improvement of bioprosthetic heart valves.

Aldehyde-induced side effects limit the clinical usefulness of bioprosthetic heart valves. Treatment of aldehyde-fixed pericardium with L-glutamic acid at pH 3.5 and storage in a nontoxic, bacteriostatic solution resulted in a lower degree of calcification in 63-day subcutaneous implants in rats (13.3 +/- 2 mg calcium per gram dry weight of tissue), as compared with commercially available tissue (169 +/- 24 mg/gm, p less than 0.05). Endothelial cells died within 1 day after seeding on the commercial tissue; however, considerable endothelial cell proliferation was measured, even 14 days after seeding on L-glutamic acid-treated pericardium. Improved biocompatibility of this alternative treatment may be due to stable chemical binding of free, reactive aldehyde groups.

Animals↗
PubMed1990

[The value of fructosamine in hemodialysis patients].

Fructosamine is thought to be an alternative diabetic long term parameter to HbAlc. A possible advantage of fructosamine is the shorter half life of this parameter. Therefore changes in the metabolic control of diabetes can be evaluated faster. However, daily variations of protein concentrations limit the clinical usefulness of fructosamine, especially in patients on hemodialysis, where we see variations in total protein- and albumin concentration during dialysis. Due to these limitations we studied the clinical usefulness of a new fructosamine assay in 38 patients with chronic renal failure. Fructosamine values, total protein, albumin, blood glucose and creatinine were measured before and after three hours hemodialysis treatment as well as glycosylated hemoglobin. Before dialysis HbA1c correlated with HbA1c after dialysis (r = 0.99), which documents the usefulness of glycosylated hemoglobin in patients on hemodialysis. Fructosamine before dialysis shows a correlation with fructosamine values after dialysis of r = 0.77. After correction with total protein the correlation was r = 0.95, also after correction with albumin. Fructosamine values before and after dialysis correlated excellently (r = 0.95). Fructosamine values before and after dialysis can only be compared after correction with total protein or with albumin.

Blood Glucose↗
PubMed1990

[Diurnal variations of fructosamine in patients with type II diabetes mellitus].

During the last years fructosamine has been presented as a measurement of diabetic long term control, particularly a shorter half life of fructosamine was seen as an advantage over HbAlc (half life of fructosamine: 16 days, half life of HbAlc: 28 days). Due to diurnal variations of fructosamine levels especially in dependence of variations of the albumin-and protein concentrations the interpretation of this parameter was somewhat limited. Recently a new colorimetric fructosamine-assay was developed. We investigated the diurnal variations of fructosamine in 28 patients with type II diabetes. Fructosamine, glucose, albumin, total protein and creatinine were measured at the times towards 3, 6, 9, 12 a.m. and 3, 6, 9, and 12 p.m. In relation to the 6 a.m. fructosamine value (= 100%) the fructosamine levels showed a daily variation from -4% at 3 a.m. to +11% at 9 a.m. Correcting fructosamine levels with total protein or with albumin reduced the variations to -1% to +6% or -3% to +9%. Daily profiles of the new fructosamine assay show a daily variation which can be minimized by correcting with protein-or with albumin concentrations. For clinical routine the daily variations especially of the corrected fructosamine levels are neglectible.

Adult↗
PubMed1990

Diagnosis of perioperative myocardial infarction by considering relationship of postoperative electrocardiogram changes and enzyme increases after coronary bypass operation.

We report the results of enzyme determinations in sera from 88 patients, 65 of whom showed inconspicuous reconvalescence, 14 who had myocardial infarction within 24 h (MI 1) after bypass surgery, and nine with myocardial infarction between 24 and 48 h postoperatively (MI 2). We wanted to determine whether the consequent measurement of activities of total creatine kinase (CK), CK isoenzyme MB (CK-MB), lactate dehydrogenase, alpha-hydroxybutyrate dehydrogenase, and aspartate aminotransferase, conducted as a part of routine laboratory diagnostics, provided meaningful information for diagnosing infarcts besides that obtained from the electrocardiogram. The postoperative mean values of the enzyme activities in blood were significantly different among the three groups; however, only a combined evaluation of CK and CK-MB by means of a discriminant analysis allowed the prediction of MI (sensitivity: MI 1 = 98.5%, MI 2 = 95.4%; specificity: MI 1 = 71.4%, MI 2 = 81.8%). CK greater than 600 U/L or CK-MB greater than 45 U/L supports the diagnosis of acute MI.

Adult↗
PubMed1990

[Purine metabolism in endothelial cells].

In human umbilical endothelial cells purine metabolism was studied: activities of some key-enzymes, concentrations of ATP, ADP, and creatine phosphate (CP), and the incorporation of labeled purine bases, purine nucleosides and glycine were measured. The results obtained show that endothelial cells are capable of degradation and synthesis of purine nucleotides. The rate of purine nucleotide synthesis via salvage pathways predominates that of de novo synthesis. Preincubation with phosphate resulted in increased nucleotide pools and incorporation of performed purines, whereas ribose showed the opposite effect. An explanation of these effects might be the limited availability of intracellular phosphoribosylpyrophosphate.

Cells, Cultured↗
PubMed1989

Thromboxane A2 generation by human umbilical endothelial cells.

Human umbilical endothelial cells were examined for their ability to release thromboxane A2 (TXA2) and prostacyclin (PGI2). We could show that the basal, unstimulated release of the two eicosanoids was inversely related to the cell density. At a density of 100,000 cells/cm2 TXA2 release was 0.062 +/- 0.28 fg/cell/h and PGI2 release was 0.184 +/- 0.051 fg/cell/h, whereas at a cell density of 20,000 cells/cm2 the cells released 1.075 +/- 0.055 fg TXA2/cell/h and 1.653 +/- 0.09 fg PGI2/cell/h. In stimulation experiments ATP and ADP significantly (p less than 0.001) increased the TXA2 and the PGI2 release. ANF caused a slow but still significant (p less than 0.001) enhancement of TXA2 release. Thrombin and ionophore A23187 caused the strongest stimulatory response, resulting in a significantly (p less than 0.001) increased release of both eicosanoids.

Data Interpretation, Statistical↗
PubMed1989

[Critical evaluation of fructosamine as a control parameter in the assessment of diabetic metabolic regulation].

For some years the glycosylated plasma proteins, the so-called fructosamines, have been used for the evaluation of metabolic control in diabetic patients. We studied the usefulness of fructosamine as an intermediate parameter in the control of diabetes and we also corrected fructosamine for serum protein. Furthermore, the dependence on daily times and amounts of food intake were examined for fructosamine alone as well as for protein-corrected fructosamine. Both parameters showed a statistically significant correlation with HbA1C (r = 0.7; P less than 0.001). Changes in the metabolic state of the diabetic patients were reflected more rapidly by both these parameters than by HbA1C. While the correction of fructosamine for serum protein eliminated its postprandial increase in the diabetic patients, circadian variation remained unchanged.

Adolescent↗
PubMed1989

Octamer transcription factors bind to two different sequence motifs of the immunoglobulin heavy chain promoter.

All promoters of immunoglobulin heavy chain genes contain three conserved sequence motifs: a heptamer motif CTCATGA, an octamer motif ATGCAAAT, and a TATA box. We show that, despite their different sequences, both the heptamer and the octamer motif are bound by the same octamer transcription factors (Oct factors, also referred to as OTFs), namely the lymphoid-specific proteins Oct-2A and Oct-2B, as well as the ubiquitous protein Oct-1. Even though binding to the octamer motif is stronger, a single heptamer motif can bind Oct proteins and mediate transcriptional activity in lymphoid cells. Furthermore, factor binding to the octamer motif facilitates binding to the nearby heptamer motif. We propose that the heptamer element plays a role early in B-cell differentiation to ensure that the heavy chain promoters are transcriptionally activated before the light chain promoters, which do not contain the heptamer motif.

Base Sequence↗
PubMed1989

17 alpha-ethinylestradiol decreases production and release of prostacyclin in cultured human umbilical vein endothelial cells.

Human umbilical vein endothelial cells (HUVEC) were incubated with the estrogen 17 alpha-Ethinylestradiol (30 ng/ml) in order to examine its regulating influence on synthesis and release of prostacyclin (PGI2). ATP (1 mg/ml) was used to stimulate PGI2-production through the purine receptors. We demonstrated that this level of estrogen decreases PGI2-synthesis by 11% and PGI2-release by 32% within 300 sec. Longer incubation times (48 hrs) resulted in the same inhibitory effect. Intracellular ATP content and methyl-3H-thymidine uptake demonstrated that the decrease of prostacyclin-concentration is not caused by reduced viability of the cells but by a direct inhibitory effect on prostacyclin synthesis and release.

Adenosine Triphosphate↗
PubMed1989

The effect of near-normoglycaemic control on plasma levels of coagulation factor VII and the anticoagulant proteins C and S in insulin-dependent diabetic patients.

The present prospective follow-up study was made to study the effect of glycaemic regulation on levels of factor VII, protein C and protein S in 15 insulin-dependent diabetic patients without manifestations of vascular disease. Patients were tested before and after 8 weeks of 'metabolic' intervention, whereby a near-normoglycaemic state was achieved. At baseline, values of cross-linked fibrin degradation products (XL-FDP) and levels of 'total' protein S were significantly increased and protein C values were decreased in the diabetic patients when compared to control subjects, whereas levels of factor VII and 'free' protein S were near normal. After 'metabolic' intervention a decrease of all haemostatic parameters were recorded, however XL-FDP levels did not decline to control levels and the imbalance of factor VII and protein C persisted. When patients with newly diagnosed diabetes (n = 8) were compared to those with long-term disease (n = 7) higher levels of factor VII, protein C and protein S were recorded in the latter group before and after metabolic intervention; at baseline the differences reached statistical significance for factor VII and protein S, and remained significant for factor VII after metabolic intervention. Before and after intervention XL-FDP levels were higher in patients with newly diagnosed disease than in patients with long-term diabetes. The correlation analysis revealed positive correlations of factor VII, protein C and protein S to cholesterol and triglycerides, of protein S to all glycaemic control parameters, negative correlations of protein C to glucose, and of XL-FDP to factor VII, protein C and protein S. The results indicate an imbalance of haemostasis towards thrombophilicity in insulin-dependent diabetic patients, not completely correctable by glycaemic control.

Adult↗
PubMed1988

Identification of a novel lymphoid specific octamer binding protein (OTF-2B) by proteolytic clipping bandshift assay (PCBA).

The octamer sequence ATGCAAAT is found in the promoters of immunoglobulin (Ig) heavy and light chain genes and in the heavy chain enhancer and is a major determinant of the cell type specific expression of Ig genes in B cells. An apparent paradox is that the same sequence serves as an upstream promoter or enhancer element in a variety of housekeeping genes such as the histone H2B and U snRNA genes. The differential usage of this regulatory sequence motif is thought to be mediated by different species of octamer binding proteins. One species of 100 kd, designated OTF-1, is present in all cell types and may exert its activating function only when it can interact with additional adjacent transcription factors. The lymphoid cell specific octamer binding protein of 60 kd (OTF-2A) specifically stimulates Ig promoters which consist essentially of a TATA-box and an octamer sequence upstream of it. Here we present evidence for yet another B cell specific octamer binding protein of 75 kd (OTF-2B). From several findings, including the absence of OTF-2B (but not OTF-2A) from a lymphocyte line that cannot respond to the IgH enhancer, we propose a role of the novel octamer factor in the long range activation by the IgH enhancer. We have used the proteolytic clipping bandshift assay (PCBA) technique to distinguish the three different forms found in B cells. This analysis indicates that the 75 kd-species OTF-2B is closely related to the 60 kd species OTF-2A.

Animals↗