Biomedical subjects

E Köhler

Publications and source records attributed to E Köhler.

At least 37 records · Page 2Linked to original sources

PubMed1994

[Hemitruncus arteriosus in an asymptomatic young man--diagnostic value of transesophageal echocardiography].

The aortic origin of one pulmonary artery, also called hemitruncus arteriosus, is a rare congenital anomaly with poor prognosis. In this report the case of an asymptomatic 18-year-old man with a systolic precordial murmur and the electrocardiographic finding of biventricular hypertrophy is described. The diagnosis of hemitruncus was confirmed by cardiac catheterization. Echocardiography showed biventricular hypertrophy and moderate enlargement of the right atrium and ventricle. In contrast to reports in children, the diagnosis could not be verified by transthoracic echocardiography because of the lack of a satisfactory acoustic window. On the other hand, the aortic origin of the right pulmonary artery and the continuation of the main pulmonary artery as left pulmonary artery were visualized by transesophageal echocardiography. However, the shunt-volume could not be determined by means of the velocity-time-integral and the diameter of the right pulmonary artery because of the turbulent blood-flow in its proximal part.

Adolescent↗

PubMed1994

Electrophoretic screening for genetic variation in apolipoprotein C-III: identification of a novel apoC-III variant, apoC-III(Asp45-->Asn), in a Turkish patient.

Screening of 6,840 plasma samples by isoelectric focusing (IEF) led to the identification of a novel apolipoprotein C-III variant. The underlying molecular defect was established by sequencing of exons 3 and 4 of the apoC-III gene subsequent to their amplification by the polymerase chain reaction (PCR). A G-->A transition in the first nucleotide of codon 45 results in a replacement of aspartic acid by asparagine. ApoC-III(Asp45-->Asn) was detected in a Turkish patient who previously had undergone coronary bypass surgery. Family studies identified two of the three children of the index patient as heterozygous variant carriers. The family was too small to demonstrate a significant effect of the variant on lipid metabolism. However, as judged by two-dimensional immunoelectrophoresis as well as IEF and subsequent scanning densitometry, the concentrations of the variant allele products were increased twofold in very low density lipoproteins (VLDL) and slightly decreased both in low density lipoproteins (LDL) and in high density lipoproteins (HDL) relative to the concentrations of the normal allele products. The disproportional distribution of the variant apoC-III isoproteins may indicate differences in the metabolism of variant and normal apoC-III. We conclude that genetically determined structural variants of apoC-III with changes in complete net charges are very rare and, hence, do not significantly contribute to the formation of dyslipidemia in the German population. Although heterozygosity for apoC-III(Asp45-->Asn) is not associated with severe dyslipidemia, the disproportional distribution of the allele products among plasma lipoproteins indirectly indicates some impact on lipoprotein metabolism.

Alleles↗

PubMed1993

Determination of the DNA bend angle induced by the restriction endonuclease EcoRV in the presence of Mg2+.

We have used the method of Zinkel and Crothers (Zinkel, S.S., and Crothers, D.M. (1990) Biopolymers 29, 29-38) to determine the degree of bending induced by the binding of the restriction endonuclease EcoRV to its recognition sequence (-GATATC-). A set of four calibration DNA fragments was constructed that contained zero, two, four, or six phased A-tracts in their centers and an EcoRV site at the 5'-end to account for the electrophoretic influence of the bound protein. The mobilities of these calibration molecules complexed with EcoRV were compared to that of a test DNA containing a central EcoRV site also complexed with EcoRV. The EcoRV-induced bend angle was found to be 44 degrees +/- 4 degrees. These experiments were performed with a catalytically inactive EcoRV mutant that still binds DNA specifically in the presence of Mg2+. In the absence of Mg2+, which is necessary for specific binding, there is no difference in the mobilities of the fragments with a peripheral or a central EcoRV site complexed with EcoRV, indicating that nonspecific binding on average does not lead to measurable DNA bending.

Base Sequence↗

PubMed1993

Glutamine/histidine polymorphism in apo A-IV affects plasma concentrations of lipoprotein(a) and fibrin split products in coronary heart disease patients.

A glutamine/histidine polymorphism at residue 360 in apolipoprotein (apo) A-IV that generates two electrophoretically detectable isoforms, apo A-IV-1 and apo A-IV-2, affects the plasma concentration of lipoprotein(a) (Lp[a]) in a healthy population. To verify this unexpected association we analyzed the effect of the apo A-IV polymorphism on Lp(a) serum concentrations in 275 male coronary heart disease patients. Allele frequencies of apo A-IV-1 and apo A-IV-2 were 0.917 and 0.083, respectively. In addition, apo A-IV-1/2 heterozygotes showed a 30% lower geometric mean concentration of Lp(a) than apo A-IV-1/1 homozygotes in this study. The relative frequency of Lp(a) concentrations > 20 mg/dl was significantly increased by a factor of 2.25 in apo A-IV-1/1 homozygotes. Other lipid parameters were not significantly affected by this apo A-IV polymorphism. Because of the relations between Lp(a) and the fibrinolytic system, we also analyzed the effect of the apo A-IV polymorphism on hemostatic variables. Apo A-IV-1/2 heterozygosity was associated with a 70% higher geometric mean plasma concentration of D-dimer, i.e., proteolytic fragments of cross-linked fibrin. Plasma concentrations of prothrombin fragments F1 + F2, fibrinogen, plasminogen, and plasminogen activator inhibitor-1 were unaffected. In conclusion, our results indicate a hitherto unappreciated role of the apo A-IV gene or a closely linked locus for the regulation of Lp(a) metabolism and hemostasis and also possibly for atherosclerosis and thrombosis.

Apolipoproteins A↗

PubMed1993

[Compliance of children with bronchial asthma in long-term therapy with theophylline retard preparations].

427 samples of the saliva of 235 children were taken on an outpatient basis to follow up long-term theophylline treatment. 37 samples from 34 children did not reveal the presence of any theophylline. The absolute non-compliance found in this manner is 21% in the 9 to 12 years age bracket and significantly higher than with the children below 9 years and above 14 years of age (8 and 10%, respectively). Better differentiation of compliance and separation from underdosing was achieved in 38 children by comparing the outpatient-controlled theophylline levels with the values obtained on an inpatient basis. For 10 patients this method definitely revealed non-compliance, whereas compliance was doubtful with 12 children and 15 children had strictly adhered to the prescribed dosage regimen. To improve the intake discipline the theophylline levels should be regularly followed up under outpatient conditions and evaluated in cooperation with the patients.

Adolescent↗

PubMed1992

Alterations of purine metabolism in mononuclear cell populations of first degree relatives of insulin-dependent diabetic individuals with disturbed glucose tolerance.

In a T lymphocyte and macrophage-depleted mononuclear cell population of the peripheral venous blood of 10 of 41 first degree relatives of insulin-dependent diabetic individuals who had or had had disturbed glucose tolerance adenine uptake rates were significantly increased, the relative adenine incorporation rates into the adenine nucleotides, however, were diminished. Values were compared with those of 30 controls. In 7 of 9 investigated individuals with increased adenine uptake rates antibody-dependent cellular cytotoxicity against rat Langerhans islets (ADCC) was increased in the same cell population. In these individuals the number of diabetes manifestations was relatively high. Adenine uptake rates, ADCC and glucose tolerance changed with time.

Adenine↗

PubMed1992

A site-directed mutagenesis study to identify amino acid residues involved in the catalytic function of the restriction endonuclease EcoRV.

We have used site-directed mutagenesis of the EcoRV restriction endonuclease to change amino acid side chains that have been shown crystallographically to be in close proximity to the scissile phosphodiester bond of the DNA substrate. DNA cleavage assays of the resulting mutant proteins indicate that the largest effects on nucleolytic activity result from substitution of Asp74, Asp90, and Lys92. We suggest on the basis of structural information, mutagenesis data, and analogies with other nucleases that Asp74 and Asp90 might be involved in Mg2+ binding and/or catalysis and that Lys92 probably stabilizes the pentacovalent phosphorus in the transition state. These amino acids are part of a sequence motif, Pro-Asp...Asp/Glu-X-Lys, which is also present in EcoRI. In both enzymes, it is located in a structurally similar context near the scissile phosphodiester bond. A preliminary mutational analysis with EcoRI indicates that this sequence motif is of similar functional importance for EcoRI and EcoRV. On the basis of these results, a proposal is made for the mechanism of DNA cleavage by EcoRV and EcoRI.

Amino Acid Sequence↗

PubMed1992

[Baclofen intoxication in chronic hemodialysis and kidney transplantation].

Fourteen days after renal transplantation, at first gave with good transplant function, a 36-year-old woman developed neurogenic dysfunction of bladder emptying. This was treated with baclofen, 5 mg three times daily by mouth. Between the 7th and 10th treatment day she progressively developed an organic psychotic syndrome and increasing respiratory paralysis after the onset of renal failure, associated with rejection of the transplanted kidney which required dialysis. Plasma concentration of baclofen was 565 ng/ml (therapeutic range 80-400 ng/ml). After discontinuing the drug and renewed haemodialysis the baclofen level rapidly fell and the symptoms receded. In a second case, a 57-year-old man on dialysis developed a thalamic pain syndrome after an intracerebral haemorrhage in the region of the basal ganglia. He was given four times 10 mg baclofen by mouth over 24 hours. 24 hours after the first dose he became deeply unconscious with respiratory failure. Plasma concentration of baclofen after the first haemodialysis period was 480 ng/ml. After 48 hours of artificial ventilation it was possible to extubate; a symptomatic transitory psychotic syndrome disappeared within 4 days. Both patients had pre-existing cerebral damage in addition to the chronic renal failure (in the first patient, meningoencephalitis 30 years previously with persisting focal lesions in the computed tomogram CT]; in the second one, residual lesions in the CT after intracerebral haemorrhage). It is emphasized that in patients who are in renal failure baclofen treatment should be undertaken cautiously: toxic signs can quickly develop especially if there is pre-existing cerebral damage.

Adult↗

PubMed1992

Mg2+ confers DNA binding specificity to the EcoRV restriction endonuclease.

The EcoRV mutant D90A which carries an amino acid substitution in its active center does not cleave DNA. Therefore, it is possible to perform DNA binding experiments with the EcoRV-D90A mutant both in the absence and in the presence of Mg2+. Like wild-type EcoRV [Taylor et al. (1991) Biochemistry 30, 8743-8753], it does not show a pronounced specificity for binding to its recognition site in the absence of Mg2+ as judged by the appearance of multiple shifted bands in an electrophoretic mobility shift assay with a 377-bp DNA fragment carrying a single EcoRV recognition sequence. In the presence of Mg2+, however, only one band corresponding to a 1:1 complex appears even with a high excess of protein over DNA. This complex most likely is the specific one, because its formation is suppressed much more effectively by a 13-bp oligodeoxynucleotide with an EcoRV site than by a corresponding oligodeoxynucleotide without an EcoRV site. The preferential interaction of the EcoRV-D90A mutant with specific DNA in the presence of Mg2+ was also demonstrated directly: a 20-bp oligodeoxynucleotide with an EcoRV site is bound with KAss = 4 x 10(8) M-1, while a corresponding oligodeoxynucleotide without an EcoRV site is bound with KAss less than or equal to 1 x 10(5) M-1. From these data it appears that Mg2+ confers DNA binding specificity to this mutant by lowering the affinity to nonspecific sites and raising the affinity to specific sites as compared to binding in the absence of Mg2+. It is concluded that this is also true for wild-type EcoRV.

Base Sequence↗

PubMed1992

Monoclonal antibody-mediated cytotoxicity against rat beta cells detected in vitro does not cause beta-cell destruction in vivo.

Two monoclonal Beta-cell surface antibodies M10H6 und K14D10 were obtained by fusion of spleen cells of Balb/c mice with the myeloma cell line P(3)0. The monoclonal antibody M10H6 was induced by immunization with rat insulinoma cells finally boostered with disintegrated rat islets, whereas the K14D10 was generated after immunization with porcine proinsulin. Both monoclonals belong to the IgG2A isotype and were screened with insulin-producing rat insulinoma cells by an indirect immunofluorescence test as well as by a cellular enzyme linked immunosorbent assay. In addition to the cell surface binding on living Beta cells the monoclonals react with islets on cryostat sections of rat pancreas. The anti-islet cytotoxic potential of these monoclonals was measured by 51Chromium-release in the presence of complement or Fc-receptor bearing leucocytes using 51Chromium-labelled rat islet cells as target. Both antibody secreting hybridomas were propagated in syngeneic mice resulting in high levels of islet cell surface antibodies in ascites and sera from the recipient. High anti-islet cytotoxicity was mediated by ascites fluid, but no mouse developed hyperglycaemia. Furthermore, the repeated injections of the monoclonals into rats did not exert a diabetogenic action and failed to reduce the pancreatic insulin content although the attraction of the K14D10 to the pancreatic islets in vivo could be demonstrated. We conclude that islet cell surface antibody-mediated Beta-cell lysis in vitro may not be relevant to Beta-cell destruction in vivo.

Animals↗

PubMed1992

[Correlation between risk profile and severity and age at manifestation of coronary heart disease--findings in 3,715 patients].

In 3715 survivors (pts) of an acute myocardial infarction (3343 males and 372 females), of ages between 20 and 80 years (mean 52.9 +/- 7.7 years), lipid-metabolism, amount of cigarette-smoking, severity of coronary artery disease (CHD) by selective coronary arteriography, and age at first manifestation of CHD documented by myocardial infarction were investigated. In contrast to normals, there is a significant reduction of disorders of lipid-metabolism with increasing age. The rate of cigarette-smoking is lower in the elderly. Females are affected by MI 3.6 to 5.3 years later than are males. There was a strong correlation between the degree of lipid-disorders and the severity of CHD, whereas the lipid-disturbances were mostly marked in the younger pts. Dependent on the degree of the underlying lipid-disorder, CHD strikes pts at a younger age, whereby the Chol/HDL-Chol-ratio is most sensitive. In a similar manner, cigarette-smoking transfers the manifestation-date of CHD "dose-dependent" to a younger age. Smokers with a daily consumption of more than 40 cigarettes are 9.2 years younger at the time of first myocardial infarction than are non-smokers. In older pts the influence of lipid-disorders and smoking becomes smaller, compared with the risk-factor "age", but it is also significant. The proven correlation between the risk-profile and the age at first myocardial event stresses the need for preventive and educative strategies.

Adult↗

PubMed1992

[Relationship between lipid metabolism disorders and age of first manifestations of coronary heart disease].

In 509 male patients, age less than 45 years, with angiographically documented coronary artery disease (CHD) we found (in contrast to age-matched controls: 459 participants of the PROCAM study) an increased amount of total cholesterol (259 vs. 221 mg/dl), LDL-cholesterol (185 vs. 142 mg/dl), Apo-B (138 vs. 118 mg/dl), lipoprotein(a) (12 vs. 5 mg/dl) and uric acid (6.4 vs. 5.8 mg/dl); HDL-cholesterol (40.5 vs. 46.8 mg/dl), Apo-A-I (122 vs. 143 mg/dl) and Apo-A-II (38 vs. 43 mg/dl) were significantly lower. These differences in lipid-metabolism between CHD-patients and controls in the younger group were essentially more pronounced than in older individuals of a group of 423 male patients over the age of 45 years who suffered from CHD and 545 age-matched PRO-CAM participants. Among the extent of the disorder in lipid metabolism, the apolipoprotein E-polymorphism, and the age of onset of CHD there exists a significant correlation which proves the special importance to therapeutically influence disorders of lipid metabolism especially in younger patients.

Adult↗

PubMed1991

Site-directed mutagenesis studies with EcoRV restriction endonuclease to identify regions involved in recognition and catalysis.

Guided by the X-ray structure analysis of a crystalline EcoRV-d(GGGATATCCC) complex (Winkler, in preparation), we have begun to identify functionally important amino acid residues of EcoRV. We show here that Asn70, Asp74, Ser183, Asn185, Thr186, and Asn188 are most likely involved in the binding and/or cleavage of the DNA, because their conservative substitution leads to mutants of no or strongly reduced activity. In addition, C-terminal amino acid residues of EcoRV seem to be important for its activity, since their deletion inactivates the enzyme. Following the identification of three functionally important regions, we have inspected the sequences of other restriction and modification enzymes for homologous regions. It was found that two restriction enzymes that recognize similar sequences as EcoRV (DpnII and HincII), as well as two modification enzymes (M.DpnII and, in a less apparent form, M.EcoRV), have the sequence motif -SerGlyXXXAsnIleXSer- in common, which in EcoRV contains the essential Ser183 and Asn188 residues. Furthermore, the C-terminal region, shown to be essential for EcoRV, is highly homologous to a similar region in the restriction endonuclease SmaI. On the basis of these findings we propose that these restriction enzymes and to a certain extent also some of their corresponding modification enzymes interact with DNA in a similar manner.

Amino Acid Sequence↗

PubMed1991

[An association of arterial occlusive disease with cyclosporine therapy after kidney transplantation].

Renal transplantation followed by immunosuppression with cyclosporine (whole-blood levels 200-300 micrograms/l) and methylprednisolone (4 mg daily) was performed in a 54-year-old man with chronic glomerulonephritis. Three years later rapidly progressive arterial obstructive disease (peripheral type) developed. Parenteral treatment with prostaglandins, calcium antagonists and nitrates, as well as a lumbar sympathectomy, was unsuccessful so that, in rapid succession, several amputations on upper and lower limbs became necessary. The disease progression was arrested only when azathioprine replaced cyclosporine. Raynaud's phenomenon, present at the time, also disappeared and analgesics were no longer required. Histological examination revealed severe Mönckeberg arteriosclerosis and thromboembolic occlusion of the affected vessels. The cyclosporine treatment, especially the hypercoagulability induced by it, and the Mönckeberg arteriosclerosis were thought to be significant factors in the pathogenesis of the rapidly progressive arterial disease. It is concluded that, in the presence of progressive arterial obstructive disease occurring under cyclosporine treatment, the replacement by other immunosuppressive agents should be considered.

Amputation, Surgical↗

PubMed1991

Effects of the platelet-activating factor antagonist BN 52021 on anti-islet cytotoxicity of mononuclear cells and serum from type 1 (insulin-dependent) diabetic patients.

The effect of platelet-activating factor (PAF) antagonist BN 52021 (0.06-2.5 mM) on the cytotoxic activity of mononuclear cells (MNC) from newly diagnosed type 1 diabetic patients against 51Cr-labeled Langerhans islets from neonatal rats was investigated in a 6-hour cytotoxicity test. A dose-dependent inhibition of anti-islet cytotoxicity by BN 52021 was observed. The suppression of the islet lysis was significant at a concentration of 0.6 mM BN 52021. During a 4-day cell culture, BN 52021 had no inhibitory effect on the antigen-mediated triggering of immunocytes with anti-islet cytotoxicity. The results suggest that the drug is only effective during immunocytolytic reactions of MNC against pancreatic islets. A PAF-independent action of BN 52021 can not be excluded at present.

Adolescent↗

PubMed1990

Increased cell-mediated cytotoxicity against beta-cells in streptozotocin-treated offspring of mother animals with gestational hyperglycaemia.

The offspring of mother animals with mild gestational hyperglycaemia exhibited basal hyperinsulinism, decreased glucose tolerance and increased susceptibility to streptozotocin diabetes. Following low-dose successive streptozotocin treatment a significantly increased spleen cell cytotoxicity against beta-cells was found in these animals as compared to the offspring of gestational normoglycaemic control mothers. Such increased cell-mediated cytotoxicity, considered as enhanced autoimmune reactivity, was positively correlated to blood glucose levels and negatively correlated to pancreatic insulin contents. Thus, hyperinsulinism, occurring during pre- and neonatal brain organization and produced by gestational hyperglycaemia, is a predisposing teratogenetic risk factor not only for the development of type II, but also of type I diabetes. Thus, it is comprehensible that the prevalence of type I diabetes in children could be decisively reduced by preventing gestational hyperglycaemia in their mothers (Dörner et al., 1985).

Animals↗

PubMed1990

Survival of islet isografts despite cytotoxicity against pancreatic islets measured in vitro.

In this study the in vivo relevance of spleen cell anti-islet cytotoxicity measured in vitro was examined by transplantation of 1,200 syngeneic islets into the spleen of rats receiving 0.5 ml complete Freund's adjuvant (CFA) 24 h before 25 mg/kg body weight streptozotocin (STZ) was given. Control rats receiving CFA or STZ alone remained normoglycaemic whereas 12 out of 21 CFA/STZ-treated rats developed a severe hyperglycaemia after three combined treatments. After the first and second combined treatment splenocytes showed a significant cytotoxicity (p less than 0.01) against syngeneic islets measured by 51Cr-release. This cytotoxicity was not detectable after the third combined treatment. The CFA/STZ-induced diabetes with a residual pancreatic insulin content of only 5% was permanently reversed by intrasplenic islet isografts, but, surprisingly, syngeneic islets survived too, if transplanted at the time when an anti-islet cytotoxicity was measured in vitro. From our results we conclude that the polyclonal activation by complete Freund's adjuvant potentiates the beta cell-toxic effect of a low dose of streptozotocin and induced a transient splenocyte-mediated anti-islet cytotoxicity not recurrent after islet transplantation. Furthermore, our findings reveal a discrepancy between organ-specific immune reactions measured in vitro and those affecting the beta cells in vivo.

Animals↗

PubMed1990

Autologous mixed lymphocyte reaction in newly diagnosed type-1 diabetes.

The autologous mixed lymphocyte reaction (AMLR) represents activation, proliferation and differentiation of T cells in response to signals from autologous non-T cells. Deteriorations in AMLR have been reported in many autoimmune diseases and in diseases with a derangement in T cell regulatory function. We have studied AMLR in 23 newly diagnosed Type-1 diabetic patients and 32 healthy subjects. T and non-T cells were purified by rosetting mononuclear cells with sheep erythrocytes and separating the rosetted T cells from the nonrosetted non-T cells by density gradient centrifugation. Purity of T-lymphocytes isolated was 90% as determined by indirect immunofluorescent analysis with monoclonal antibodies. Proliferation of lymphocytes was measured in response to phytohaemagglutinin and of concanavalin A in a lymphocyte transformation test. In the present study, a deficient AMLR is demonstrated in patients with newly diagnosed Type-1 diabetes. Our data provide evidence for an aberrant immune regulation at the time of diabetes manifestation. The deficient AMLR may represent the in-vitro expression of an in-vivo process against pancreatic cells.

Adolescent↗