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Biomedical subjects

G Assmann

Publications and source records attributed to G Assmann.

At least 181 records · Page 10Linked to original sources
PubMed1996

Interleukin-6 correlates with hemodynamic impairment during dobutamine administration in chronic heart failure.

Proinflammatory cytokines have been implicated in the pathophysiology of chronic heart failure. We determined mixed venous levels of interleukin-6 (IL6) in 18 heart transplant candidates before, 1, 4, and 24 h after initiation of dobutamine infusion (3 micrograms/kg/min) during hemodynamic evaluation. During the first 4 h of dobutamine, systemic vascular resistance decreased (1358 to 1024 dyn x s x cm-5, P = 0.01) while cardiac index (2.3 to 2.9 l/min/m2, P = 0.008) increased. Both returned to baseline after 24 h. IL6 was elevated at baseline compared to age-matched controls (1.5 (0/4.3) vs. 0 (0/0.5) P = 0.003). There was an increase in IL6 from 1.5 (0/4.3) to 3.6 (0.3/5.3) pg/ml after 24 h (P = 0.04). We found higher IL6 levels in the sicker half of patients as defined by pulmonary capillary wedge pressure > 24 mmHg (P = 0.005), mean pulmonary arterial pressure > or = 35 mmHg (P = 0.01), right atrial pressure > 13 mmHg (P = 0.02), and heart rate > or = 87/min (P = 0.02) as well as mean arterial pressure < 82 mmHg (P = 0.005). In conclusion, in this pilot study IL6 correlates with the severity of chronic heart failure during low dose dobutamine infusion.

Adult↗
PubMed1996

Defective regulation of phosphatidylcholine-specific phospholipases C and D in a kindred with Tangier disease. Evidence for the involvement of phosphatidylcholine breakdown in HDL-mediated cholesterol efflux mechanisms.

The negative correlation between coronary heart disease and plasma levels of HDL has been attributed to the ability of HDL to take up cellular cholesterol. The HDL3-induced removal of cellular cholesterol was reported to be impaired in fibroblasts from patients with familial HDL deficiency (Tangier disease, TD). In addition, we have recently shown that HDL3 stimulates the hydrolysis of phosphatidylcholine (PC) in cholesterol-loaded fibroblasts. To investigate whether this cell signaling pathway is involved in cholesterol efflux mechanisms, we compared the HDL3-induced PC hydrolysis in normal fibroblasts and in fibroblasts from a TD kindred, in whom the HDL3- and apolipoprotein A-I (apo A-I)-induced mobilization of cellular cholesterol was found to be reduced by 50%. The HDL3-induced formation of phosphatidic acid (PA) via PC-specific phospholipase D (PC-PLD) was markedly reduced by 60-80% in these cells, whereas the formation of diacylglycerol (DG) via PC-specific phospholipase C (PC-PLC) was two- to threefold enhanced. Defective regulation of PC-PLC and PC-PLD was similarly observed in response to apo A-I and endothelin, but not in response to the receptor-independent stimulation of PC hydrolysis by PMA. A Tangier-like PA and DG formation pattern could be induced in normal cells after preincubation with pertussis toxin, suggesting the involvement of a G-protein. The impaired mobilization of radiolabeled cellular cholesterol in TD cells could completely be overcome by increasing the PA levels in the presence of the PA phosphohydrolase inhibitor propranolol. Conversely, the inhibition of PA formation in the presence of 0.3% butanol as well as the inhibition of DG formation in the presence of the PC-PLC inhibitor D 609 reduced the mobilization of cellular cholesterol both in normal and in TD cells. Our data indicate that the coordinate formation of PA and DG via PC-PLD and PC-PLC is essential for efficient cholesterol efflux. The molecular defect in this TD kindred appears to affect an upstream effector of protein kinase C responsible for the G-protein-dependent regulation of PC-specific phospholipases.

Apolipoprotein A-I↗
PubMed1996

Isolation of prostate-derived single cells and cell clusters from human peripheral blood.

The detection of blood-borne prostate cancer (PCA) cells may help with clinical staging and the further understanding of PCA metastases. We discovered prostate-specific antigen (PSA)-positive stained but not PSA mRNA-expressing blood cells by means of cell sorting and PSA reverse transcription-PCR in patients. Therefore, we developed a cytokeratin immunomagnetic method to isolate PSA-positive epithelial cells from the circulating blood of PCA patients. We obtained blood-borne single cells from 6 of 10 PCA patients and clustered cells from 8 of 10 PCA patients. Patients with benign prostate hyperplasia tested negative for cell clusters. The reported isolation method yielded prostate-derived cells or clusters of them from PCA-diagnosed patients.

Humans↗
PubMed1996

Compound heterozygosity for a structural apolipoprotein A-I variant, apo A-I(L141R)Pisa, and an apolipoprotein A-I null allele in patients with absence of HDL cholesterol, corneal opacifications, and coronary heart disease.

BACKGROUND: The concentration of HDL cholesterol is inversely correlated with the risk of coronary heart disease (CHD). Some rare mutations in the apolipoprotein (apo) A-I gene are associated with low levels of HDL cholesterol. Their association with cardiovascular risk is controversial. METHODS AND RESULTS: We studied the molecular defects underlying corneal opacities and absence of HDL cholesterol in three brothers and a sister. In a family study, the importance of these defects for lipid metabolism and manifestation of coronary heart disease was investigated. The frequency of these apo A-I defects was assessed by genotype and phenotype analysis of 477 DNA- and plasma samples, respectively, from the population. The four patients were compound heterozygotes for a null allele and a missense mutation in the apo A-I gene that leads to a leucine-->arginine substitution at residue 141 [apo A-I(L141R)Pisa]. Heterozygotes for either the null allele or the structural variant had half-normal concentrations of HDL cholesterol and apo A-I compared with unaffected family members. Apo A-I(L141R)Pisa was detected in one more unrelated subject. Coronary angiography of the four compound heterozygotes revealed the presence of CHD in all male patients, whose ages ranged between 45 and 52 years. They presented with additional risk factors, including elevated LDL cholesterol levels, obesity, and arterial hypertension. Despite complete HDL deficiency and hypercholesterolemia, CHD was absent in the 51-year-old premenopausal sister. CONCLUSIONS: Apo A-I deficiency may lead to premature atherosclerosis if present in conjunction with additional cardiovascular risk factors.

Adolescent↗
PubMed1996

Immunophenotyping of lymphocytes obtained by bronchoalveolar lavage: description of an all-purpose tricolor flow cytometric application.

A tricolor flow cytometric application is described which permits the determination of total T lymphocytes, T helper lymphocytes and cytotoxic T lymphocytes, natural killer cells and activated T lymphocytes under the same experimental conditions. Even when the lymphocyte count is low, when there is contamination by dust particles or when the cells are damaged the method works with high specificity and reliability. Lymphocytes are identified on the basis of their expression of the pan-leucocyte marker CD45, their side scatter, and plasma membrane integrity, assessed using the fluorescent DNA dye LDS 751. When lymphocyte subsets assessed by flow cytometry were compared with the standard immunoperoxidase method, a strong correlation was found for the CD3+, CD4+ and CD8+ cells. A weak correlation was found for CD25+ cells (r = 0.5). No correlation was seen for CD56+ cells. The high specificity of the procedure suggests that it could be used routinely for the analysis of lymphocytes in bronchoalveolar lavage fluid (BALF), especially when the BALF is contaminated by inorganic particles. Furthermore the application may contribute to the evaluation of lymphocyte subset analysis in the presence of low cell counts.

Bronchoalveolar Lavage Fluid↗
PubMed1996

An intronic mutation in a lariat branchpoint sequence is a direct cause of an inherited human disorder (fish-eye disease).

The first step in the splicing of an intron from nuclear precursors of mRNA results in the formation of a lariat structure. A distinct intronic nucleotide sequence, known as the branchpoint region, plays a central role in this process. We here describe a point mutation in such a sequence. Three sisters were shown to suffer from fish-eye disease (FED), a disorder which is caused by mutations in the gene coding for lecithin:cholesterol acyltransferase (LCAT). Sequencing of the LCAT gene of all three probands revealed compound heterozygosity for a missense mutation in exon 4 which is reported to underlie the FED phenotype, and a point mutation located in intron 4 (IVS4:T-22C). By performing in vitro expression of LCAT minigenes and reverse transcriptase PCR on mRNA isolated from leukocytes of the patient, this gene defect was shown to cause a null allele as the result of complete intron retention. In conclusion, we demonstrated that a point mutation in a lariat branchpoint consensus sequence causes a null allele in a patient with FED. In addition, our finding illustrates the importance of this sequence for normal human mRNA processing. Finally, this report provides a widely applicable strategy which ensures fast and effective screening for intronic defects that underlie differential gene expression.

Amino Acid Sequence↗
PubMed1996

Diadenosine polyphosphates regulate cytosolic calcium in human fibroblast cells by interaction with P2x purinoceptors coupled to phospholipase C.

The effects of diadenosine pentaphosphate (AP5A), and diadenosine hexaphosphate (AP6A) on the cytosolic-free Ca2+ concentration ([Ca2+]i) were evaluated in cultured human fibroblast cells (HF cells) using the fluorescent dye technique. AP5A, and AP6A concentration-dependently increased [Ca2+]i in HF cells. The addition of 10 mumol/1 AP5A and AP6A significantly increased [Ca2+]i in HF cells from 71 +/- 3 nmol/1 (n = 184) to 241 +/- 39 nmol/1 (n = 11; P < 0.001 compared to resting value) and to 227 +/- 26 nmol/1 (n = 23; P < 0.001), respectively. The purinoceptor P2 blockers, suramin and pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), inhibited the diadenosine polyphophate-induced [Ca2+]i increase, whereas the P2y purinoceptor blocker, reactive blue, had no effect. Adenosinetriphosphate (ATP) and the P2x agonist, alpha 1 beta-methylene-ATP also significantly increased [Ca2+]i in HF cells, whereas the P2y agonist methylthio-ATP showed only a small [Ca2+]i response. Diadenosine polyphosphates mainly induced transplasmamembrane Ca2+ influx as was confirmed by experiments in the absence of extracellular Ca2+ or by manganese quenching studies. Organic (verapamil) and inorganic Ca2+ channel blockers (NiCI2) significantly reduced the AP6A induced transplasmamembrane Ca2+ influx. The inhibitor of phosphatidylcholine-specific phospholipase C, D609, significantly reduced the effect of diadenosine polyphosphates on [Ca2+]i in HF cells. It is concluded that diadenosine polyphosphates regulate transplasmamembrane Ca2+ influx after occupation of P2x receptors via activation of phosphatidylcholine-specific phospholipase C and hence of voltage-operated Ca2+ channels.

Bridged-Ring Compounds↗
PubMed1996

Phospholipid transfer protein mediated conversion of high density lipoproteins generates pre beta 1-HDL.

High density lipoproteins (HDL) subclasses can be differentiated by two-dimensional non-denaturing polyacrylamide gradient gel electrophoresis (2D-PAGGE) and subsequent immunoblotting. The quantitatively minor HDL-subclasses pre beta 1-LpA-I and gamma-LpE are initial acceptors of cell-derived cholesterol into the plasma compartment. In this study we analysed the effect of phospholipid transfer protein (PLTP) on the electrophoretic distribution of HDL-subclasses in plasma as well as the ability of plasma, pre beta 1-LpA-I, and gamma-LpE to take up [3H]cholesterol from labeled fibroblasts. Pre beta 1-LpA-I but not gamma-LpE disappeared during a 16 hours incubation in the absence of PLTP. During a one minute incubation pre beta 1-LpA-I of pre-incubated plasma released 75% less [3H]cholesterol from radiolabeled fibroblasts than pre beta 1-LpA-I of control plasma. Pre-incubation of plasma reduced the uptake of [3H]cholesterol by gamma-LpE by 40%. Totally, the cholesterol efflux capacity of plasma decreased by 10% compared to the original sample. The amount of immunodetectable pre beta 1-LpA-I increased when plasma was incubated in the presence of PLTP while the amount of immunodetectable gamma-LpE did not change. After one minute incubation of PLTP-conditioned plasma with [3H]cholesterol-labeled fibroblasts, the amount of radioactive cholesterol taken up by pre beta 1-LpA-I was twice as high as in control plasma whereas the amount of [3H]cholesterol taken up by gamma-LpE remained unchanged. As a net result, treatment with PLTP increased the cholesterol efflux into total plasma by 40%. Together with results of previous studies our data suggest that the conversion of alpha-LpA-I3 into alpha-LpA-I2 by PLTP generates pre beta 1-LpA-I but not gamma-LpE. PLTP helps to enhance the uptake of cell-derived cholesterol by pre beta 1-LpA-I and, thereby, the cholesterol efflux capacity of normal plasma.

Apolipoprotein A-I↗
PubMed1996

Hypertriglyceridemia and elevated lipoprotein(a) are risk factors for major coronary events in middle-aged men.

Cardiovascular risk factors were analyzed in 4,849 male participants, aged 40 to 65 years, in an 8-year follow-up of the Münster Heart Study (Prospective Cardiovascular Münster Study; PROCAM). One hundred eighty-one definite nonfatal myocardial infarctions, 49 fatal myocardial infarctions, and 28 sudden cardiac deaths were observed. Multiple logistic function analysis confirmed that age, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, systolic blood pressure, cigarette smoking, diabetes mellitus, angina pectoris, and family history of myocardial infarction were important cardiovascular risk factors. Interestingly, this analysis revealed a significant and independent association between serum levels of triglycerides and the incidence of major coronary events. The relation between lipoprotein(a) [Lp(a)] levels and the occurrence of major coronary events was analyzed in a subgroup of 878 men. Thirty-three probands with major coronary events had significantly higher geometric mean levels of Lp(a) than 828 men who did not experience major coronary events (0.09 vs 0.05 g/L; p <0.011). Thus, in addition to established risk for factors, serum levels of triglycerides and Lp(a) are sensitive indicators of increased risk major coronary events.

Adult↗
PubMed1996

Detection of the metastatic potential of blood-borne and immunomagnetically enriched epithelial cells by quantitative erbB-2 RT-PCR.

A quantitative competitive RT-PCR targeting the specific mRNA of c-erbB-2 is described. It is well known that in many cancers the c-erbB-2 gene dosage is elevated and/or the mRNA is overexpressed leading to a poor prognosis. The recently established method to enrich epithelial cells from peripheral blood made it reasonable and logical to develop a sophisticated competitive RT-PCR method to estimate the c-erbB-2 mRNA load of such cells. By this enrichment method it was discovered that cancer cells can be either isolated as single cells or clusters from patients' blood. The plausibility for their metastatic potential is derived from the measurement of the c-erbB-2 mRNA expression. A SKBR3 cell model suggested that the c-erbB-2 mRNA load is between 168 and 336 molecules per cell. Results of the quantitative competitive RT-PCR method can be used as a rational to determine the efficiency of anti-oncogenic therapies and as a criterion in adjuvant therapy decision.

Adenocarcinoma↗
PubMed1996

A missense mutation (Thr-6Pro) in the lysosomal acid lipase (LAL) gene is present with a high frequency in three different ethnic populations: impact on serum lipoprotein concentrations.

A frequent missense mutation (Thr-6Pro) found in the prepeptide of the lysosomal acid lipase (LAL) gene was analyzed in a cohort of 1003 randomly selected samples from Germany, Japan and Sardinia (Italy). Using the mutagenically separated polymerase chain reaction (MS-PCR), allele frequencies of 0.269, 0.238 and 0.245 were determined in the three populations, respectively. Statistical analysis showed a lack of association with a dyslipidemic phenotype in all three groups. Additionally, in a subgroup of 126 German individuals no association was observed between genotype and LAL activity. We conclude that this mutation appears to be a frequent LAL gene polymorphism causing no impaired function of the enzyme and no measurable dyslipidemia in the general population.

Base Sequence↗
PubMed1996

High-density lipoprotein cholesterol as a predictor of coronary heart disease risk. The PROCAM experience and pathophysiological implications for reverse cholesterol transport.

The incidence of coronary heart disease (CHD) was assessed via the Prospective Cardiovascular Münster (PROCAM) study in 19,698 volunteer subjects aged between 16 and 65 years. An adequate incidence of atherosclerotic CHD was only found in male subjects greater than 40 years of age. The analysis and subsequent 6 year follow-up period was, therefore, confined to 4559 male participants aged 40-64 years. In the follow-up period, 186 study participants developed atherosclerotic CHD (134 definite non-fatal myocardial infarctions (MIs) and 52 definite atherosclerotic CHD deaths including 21 sudden cardiac deaths and 31 fatal MIs). Univariate analysis revealed a significant association between the incidence of atherosclerotic CHD and high-density lipoprotein cholesterol (P < 0.001), which remained after adjustment for other risk factors.

Adolescent↗