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Biomedical subjects

U Keller

Publications and source records attributed to U Keller.

At least 127 records · Page 7Linked to original sources
PubMed1995

Differences in the phenotypic characteristics of subjects with familial defective apolipoprotein B-100 and familial hypercholesterolemia.

Familial defective apolipoprotein B-100 (FDB) is a recently identified autosomal-dominantly inherited disorder caused by a point mutation in the apolipoprotein (apo) B gene. To determine whether the phenotypic characteristics in FDB subjects are similar to those in subjects with familial hypercholesterolemia (FH), 76 kindreds fulfilling the clinical criteria for heterozygous FH/FDB were characterized using molecular biological techniques. Allele-specific polymerase chain reaction (PCR) at the apoB locus was used for diagnosis or exclusion of FDB. PCR-based methods for detection of two point mutations (V408M and P664L) at the LDL receptor (LDLR) locus, cosegregation analysis using eight restriction fragment length polymorphisms (RFLPs) at the LDLR locus, or the exclusion of FDB confirmed the clinical diagnosis of FH. Three kindreds were not included because of a missing cosegregation between a particular haplotype and the FH phenotype. We predicted that a similar number of kindreds would be detected in the two groups, assuming comparable prevalences of the diseases in our population and similar phenotypic characteristics. However, only nine kindreds were identified with the FDB mutation compared with 64 kindreds with FH (P < .0001). From these 73 kindreds, 28 FDB heterozygotes and 129 FH heterozygotes were compared using multivariate analysis. There were no differences between these two groups with respect to age, sex, and apoE genotype distribution, lipoprotein(a) concentrations, body mass index, blood pressure, and smoking habits. However, FDB subjects demonstrated significantly lower concentrations of total cholesterol (8.1 versus 10.2 mmol/L, P < .001), LDL cholesterol (6.3 versus 8.2 mmol/L, P < .001), and triglycerides (1.3 versus 1.8 mmol/L, P = .025) and higher concentrations of HDL cholesterol (1.4 versus 1.2 mmol/L, P = .015) than subjects with FH. In contrast to FH, female FDB subjects tended to have higher concentrations of total cholesterol (8.9 versus 7.5 mmol/L, P = .032) and LDL cholesterol (7.1 versus 5.7 mmol/L, P = .026) than FDB males. The same results regarding total and LDL cholesterol and sex differences were observed when individual data of 238 FDB and 415 FH subjects from the literature were compared. In addition, FDB subjects showed much larger total cholesterol fluctuations than FH subjects (median of intraindividual coefficients of variation: FDB, 14.5%; FH, 5.3%; P < .001). In summary, these results demonstrate that FDB subjects tend to have a milder form of hyperlipoproteinemia than FH subjects and that only a part of the subjects with FDB fulfill the established criteria for identifying FH.

Adolescent↗
PubMed1995

[Why does nutrition therapy so often fail in non-insulin-dependent diabetes? What measures bring success?].

It is a common belief among physicians that nutritional therapy in type II diabetic subjects is inefficient because the patients do not comply with the recommendations. Failure of a therapeutic response leads to feelings of guilt in patients, followed by frustration, and refusal of further treatment. The physician rapidly starts with drug or insulin therapy before the effects of diet treatment are assessable. Nutritional recommendations for diabetics are basically the same as for non-diabetics. Successful dietary treatment of obese type II diabetic subjects requires realistic goals regarding weight loss. Frequent mistakes are that an ideal body weight is aimed for, and that the patients are asked to omit only carbohydrates in the diet. Splitting of the meals, and distribution of carbohydrate-containing foods to individual meals during the day are important components of a meal plan. The patient should also be counciled how to avoid visible and invisible dietary fats. Exchange lists are frequently administered, but they fail, because they are too complicated. Only a part of decompensated type II diabetic subjects respond to weight loss. The response is evident already after a few [2.3 kg] weight loss. Other diabetic subjects fail to improve their glucose control after weight loss. These patients require an alternative treatment, i.e. oral antidiabetic agents or insulin. Frequently behavior therapy is of advantage in obese type II diabetic subjects, in addition to longterm dietary treatment. Dieticians should be involved in all difficult cases since they have the necessary experience to perform this longterm treatment.

Behavior Therapy↗
PubMed1994

Regulation of cytokine expression by interferon-alpha in human bone marrow stromal cells: inhibition of hematopoietic growth factors and induction of interleukin-1 receptor antagonist.

We investigated the effects of interferon-alpha (IFN-alpha) on the expression of cytokines by human bone marrow stromal cells. Production of granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte-CSF (G-CSF), and interleukin-1 beta (IL-1 beta) in stromal cell layers was induced by incubation with IL-1 alpha, tumor necrosis factor (TNF), or lipopolysaccharide (LPS). Addition of IFN-alpha to such stimulated cultures resulted in a strong downregulation of mRNA expression of GM-CSF and IL-1 beta. Similarly, the protein levels of GM-CSF and IL-1 beta were significantly reduced by IFN-alpha, whereas G-CSF production was only moderately inhibited. In contrast, IFN-alpha markedly stimulated the production of IL-1 receptor antagonist (IL-1RA) by stromal cells. The inhibition of cytokine expression resulted in a reduced hematopoietic activity of stromal cells, indicated by a reduced proliferation of the factor dependent cell line MO7e on IFN-alpha-treated stromal cells. In the presence of cycloheximide (CHX), IFN-alpha failed to inhibit IL-1 mRNA expression, whereas the regulation of GM-CSF and IL-1RA by IFN-alpha was not affected. Our results indicate that the myelosuppressive effects of IFN-alpha, as observed in therapeutic applications or associated with viral infections, are, in part, indirectly mediated by inhibition of the paracrine production of hematopoietic growth factors.

Base Sequence↗
PubMed1994

Human interleukin-4 enhances stromal cell-dependent hematopoiesis: costimulation with stem cell factor.

Interleukin-4 (IL-4) has distinct hematopoietic activities, primarily as a costimulant with other cytokines to enhance colony formation of hematopoietic progenitors. We investigated the influence of IL-4 on stromal cell-supported long-term cultures (LTCs) of normal human bone marrow. Addition of IL-4 to LTCs of unseparated bone marrow or highly enriched CD34+ cells resulted in a significant increase of myeloid progenitors in the nonadherent, as well as in the stromal cell-adherent cell populations. In contrast, the total cell number was not influenced by IL-4, suggesting a selective effect on primitive progenitor cells. Cord blood cells or CD34+ bone marrow cells were incubated with stem cell factor (SCF) and/or IL-4 in stromal cell-free cultures. In these experiments, a twofold to fivefold increase of myeloid progenitor cells was observed in the presence of SCF and IL-4 as compared with SCF alone. Preincubation of the stromal cell cultures with IL-4 resulted in an enhanced adherence of CD34+ cells to the stromal layer. Secretion of hematopoietic growth factors produced by the stromal cells, such as granulocyte-macrophage colony-stimulating factor (G-CSF), and IL-1, was inhibited by IL-4. Thus, the increase of hematopoietic progenitors in LTCs, as observed in the presence of IL-4, can be at least partially explained by a costimulation of SCF and IL-4 on primitive progenitor cells and by an enhancement of hematopoietic cells to stroma. The downregulation of CSFs by IL-4 might prevent the expansion of the mature hematopoietic cell compartment.

Antigens, CD↗
PubMed1994

Epimerization of the D-valine portion in the biosynthesis of actinomycin D.

In the biosynthesis of actinomycin, the multifunctional actinomycin synthetase II (ACMS II) assembles 4-methyl-3-hydroxyanthranilic acid (4-MHA), L-threonine and D-valine, the first three residues of the 4-MHA peptide lactone chain. ACMS II activates L-threonine and L-valine but not D-valine as thioesters via their adenylates, and there is no epimerization of the covalently bound L-valine. When L-threonine and L-valine are presented to the enzyme together with the 4-MHA analogue p-toluic acid and the 4-MHA-activating enzyme ACMS I, ACMS II forms the two diastereomers p-toluyl-L-Thr-L-Val and p-toluyl-L-Thr-D-Val in equal amounts along with p-toluyl-L-Thr in a cofactor-independent manner. Studies with [2,3-3H2]valine revealed that p-toluyl-L-Thr-D-Val contained approximately 50% of the tritium label found in the LL-diastereomer. Concomitantly, radioactive water was formed due to enzyme-catalyzed hydrogen exchange with the solvent during epimerization. In the absence of threonine (or MgATP), however, the amount of radioactive water formed from [3H]valine was significantly less, which suggests that the peptide bond between L-threonine and L-valine is formed prior to the epimerization at C-2 of valine. The facts that both LL- and LD-acyldipeptides are equally present on the enzyme's surface--as revealed by using 14C-labeled threonine or valine as precursors--and that the L-valine in the LL-diastereomer apparently has not lost hydrogen strongly suggests that the LL-diastereomer is an obligatory intermediate in the formation of the LD-dipeptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Streptomyces chrysomallus FKBP-33 is a novel immunophilin consisting of two FK506 binding domains; its gene is transcriptionally coupled to the FKBP-12 gene.

The nucleotide sequence of the region 5' to the fkbA gene, encoding the Streptomyces chrysomallus FK506 binding protein (FKBP-12), revealed an open reading frame (fkbB) encoding a protein of 312 amino acids, with an M(r) of approximately 33,000. FkbB and fkbA appear to be co-transcribed under the control of a promoter upstream of fkbB. The presumptive protein encoded by fkbB would be an FKBP (designated FKBP-33) consisting of two FK506 binding domains with 43 and 32% sequence identity to FKBP-12 and a signal peptide sequence characteristic of bacterial membrane lipoproteins. The portion of the gene comprising the two FKBP domains, as well as each individual domain, were expressed as fusion proteins in Escherichia coli and purified. Each expressed domain, as well as FKBP-33 itself, possesses peptidyl-prolyl cis-trans isomerase activity, though with much lower specific activities than FKBP-12. FKBP-33 is located in the cell membrane of S.chrysomallus and of other streptomycetes, as predicted from the presence of the signal peptide sequence. Pulse-chase experiments with radioactive palmitate in whole cells revealed significant labelling of FKBP-33, which probably carries palmitate at its N-terminus and an additional diacylglycerol residue attached to the N-terminal cysteine in thioether linkage. The two domains of FKBP-33 showed considerable homology with numerous eukaryotic and prokaryotic FKB domains. Calculations of phylogenetic relationships indicate with high probability that the two domains of the protein have arisen by a double gene duplication of fkbA lying in tandem to fkbB.

Amino Acid Isomerases↗
PubMed1994

Prediction of the therapeutic response to simvastatin by pretreatment lipid concentrations in 2082 subjects.

2082 hypercholesterolemic subjects were treated with simvastatin for 12 weeks. In 530 patients the dose was increased after 6 weeks from 10 to 20 mg because of persistently high cholesterol concentrations. Total cholesterol (TC) in the 1552 patients taking 10 mg fell by 1.61 mmol.l-1 (18.4%), LDL cholesterol (LDLC) by 1.53 mmol.l-1 (25.2%), and triglycerides (TG) by 0.13 mmol.l-1 (5.5%); HDL cholesterol (HDLC) significantly increased by 0.05 mmol.l-1 (3.6%). In the 530 patients taking 20 mg TC fell by 1.89 mmol.l-1 (19.9%), LDLC by 1.78 mmol.l-1 (26.0%), and TG by 0.13 mmol.l-1 (5.5%); HDLC increased by 0.05 mmol.l-1 (3.7%). The reductions in TC, LDLC, and TG were positively correlated and the increase in HDLC negatively correlated with their respective baseline values. There were independent significant correlations of the fall in LDLC with sex (MANOVA), baseline TG, and adherence to a lipid-lowering diet. The falls in TG significantly correlated with baseline fructosamine concentrations and dietary adherence. There were 571 adverse events in 16.6% of the patients but no case of myopathy. These results show that simvastatin is usually well tolerated and that its effects on TC and LDLC depend on their baseline concentrations.

Adult↗
PubMed1994

Immunofluorescence of mineralocorticoid receptors in peripheral lymphocytes: presence of receptor-like activity in patients with the autosomal dominant form of pseudohypoaldosteronism, and its absence in the recessive form.

Pseudohypoaldosteronism is a syndrome characterized by salt wasting and a failure to thrive due to the resistance towards the action of aldosterone. Aldosterone levels and plasma renin activity are extremely elevated and aldosterone binding sites in peripheral mononuclear leukocytes have regularly shown to be reduced or absent. Sporadic as well as familial cases have been identified and an autosomal dominant as well as an autosomal recessive mode of inheritance has been described. A defect in the aldosterone receptor has been postulated, however, molecular genetic analysis in selected patients has not revealed a mutation in the sequence of the coding region of the cDNA of the mineralocorticoid receptor gene. In the present study we have used a fluorescence-labeled antibody to detect possible receptor expression in monocytes from patients with various clinical forms of pseudohypoaldosteronism. Patients with the sporadic as well as with the autosomal dominant form were clearly immunopositive despite being negative in terms of aldosterone receptor binding. In contrast in two patients with the autosomal recessive form there was no detectable receptor protein, consistent with the results obtained in the aldosterone binding studies. These results suggest that the pathogenesis of pseudohypoaldosteronism is heterogeneous not only regarding the mode of inheritance but also in terms of receptor binding. Thus, in a subgroup of patients the inability of the receptor to bind ligand may be due to a defect involving other, probably cellular factors rather than a deficiency or a defect in the mineralocorticoid receptor system itself.

Adult↗
PubMed1994

Androgen binding sites in peripheral human mononuclear leukocytes of healthy males and females.

Androgen binding sites have been identified in circulating human mononuclear leukocytes of healthy donors of both sexes. Cells were separated from blood samples on a Ficoll gradient and incubated with different concentrations of [3H]testosterone in the presence or absence of a 400-fold excess of unlabelled testosterone. Binding data were derived from Scatchard analysis. The binding sites fulfil the required criteria for specific steroid binding sites however differ somewhat from the classic androgen receptors from genital skin fibroblast: in fertile adult males (n = 20) the binding sites showed (1) a high affinity for testosterone (1.32 +/- 0.49 nM; mean +/- SD), (2) a saturable capacity (184 +/- 52 binding sites per cell; mean +/- SD), and (3) a characteristic competitive binding profile for other steroid hormones (relative binding affinities: testosterone = dihydrotestosterone > 17 beta-estradiol > progesterone, whereas aldosterone, 17-hydroxy-progesterone and cortisol did not compete appreciably). Furthermore the number of binding sites determined using [3H]dihydrotestosterone, [3H]RU-1881, or [3H]testosterone were comparable. This raises the possibility that androgen receptors in peripheral mononuclear leukocytes differ from those in genital skin fibroblasts. There was no apparent correlation between serum testosterone concentrations and androgen binding sites. In fertile women remarkable changes in androgen binding sites were seen in the course of the menstrual cycle, with a significant increase in the immediate preovulatory period. The presence of androgen receptors in peripheral mononuclear leukocytes provides for the first time the experimental basis for an hypothesis of direct, receptor-mediated effects of androgens on mature immunocompetent cells. The immunological implications of these results are discussed.

Adult↗
PubMed1994

Psychological and metabolic effects of dietary carbohydrates and dexfenfluramine during a low-energy diet in obese women.

Dietary carbohydrates and dexfenfluramine (dF) have been shown to influence serotoninergic neurotransmission. To assess their effect on spontaneous physical activity, mood, sleep quality, and resting metabolic rate (RMR), 32 obese females were studied while consuming diets providing 3970 kJ (950 kcal)/d. They were randomly allocated to either a diet relatively high in carbohydrates (carbohydrate:fat:protein, 49%:22%:29% of energy intake; group 1) or to a diet relatively high in fat (carbohydrate:fat:protein, 12%:59%:29%); subjects receiving the latter diet were treated additionally with either 30 mg dF (group 2) or placebo (group 3) daily in a double-blind fashion. Spontaneous physical activity decreased in the group treated with dF compared with the other two groups (P = 0.0002). Daily self-rated questionnaires indicated that mood and tiredness were negatively affected in two groups after the first week. Subjects treated with dF lost more weight than did those in the other two groups (P = 0.013). This occurred despite a decrease in physical activity and unchanged energy intake and resting energy expenditure.

Adult↗
PubMed1994

[Prevention of coronary heart disease in familial hypercholesterolemia].

Familial forms of isolated hypercholesterolemia are inherited autosomal-dominantly and are caused by defects of the low-density lipoprotein (LDL) receptor protein or its ligand, the apolipoprotein B-100, the exclusive apolipoprotein moiety of the LDL particles. Mutations at the LDL receptor gene locus (more than 150 different mutations have been described up to now) lead to familial hypercholesterolemia (FH); the only mutation at the apolipoprotein B-100 gene locus described in detail so far leads to the so-called familial defective apolipoprotein B-100 (FDB). Both lipid disorders are characterized by an increased risk for premature atherosclerosis involving primarily the coronary arteries. An increased risk for coronary heart disease can be expressed statistically by the excess mortality. In particular, individuals between the age of 20 and 59 are affected by an excess mortality; coronary deaths are approximately 100 times more frequent in patients between 20 and 39 with familial forms of hypercholesterolemia than within the normal population. On the other hand, in patients with myocardial infarctions before the age of 60, the diagnosis of FH is approximately 20 to 30 times more frequent than within the normal population. A regression of cardiovascular lesions subsequent to an intensive lipid-lowering therapy has clearly been demonstrated in patients with familial forms of hypercholesterolemia. Because of the serious prognosis of untreated familial forms of isolated hypercholesterolemia with respect to longevity, it is important to identify patients and their relatives with FH and FDB as early as possible and to treat them, besides a lipid-lowering diet, intensively with lipid-lowering drugs.

Adult↗
PubMed1994

High prevalence of familial defective apolipoprotein B-100 in Switzerland.

Familial defective apolipoprotein B-100 (FDB) is caused by a single G-to-A substitution at nucleotide 10,708 leading to an arginine to glutamine change at amino acid 3,500 of the apolipoprotein B-100 and thus, a reduced binding of the apolipoprotein B to the low density lipoprotein (LDL) receptor. In the present study, the prevalence of FDB in Switzerland was estimated, on the one hand, from a sample of 728 healthy volunteers whose origin was spread out over the entire German, French, and Romansh speaking parts of the country, and, on the other hand, from 142 unrelated Swiss families with primary hypercholesterolemia comprising 520 individuals. Using polymerase chain reaction (PCR)-based methods, three individuals were identified with the point mutation in the sample of volunteers, equivalent to a prevalence of approximately 1/240 (90% confidence interval: 1.51 x 10(-3)-1.03 x 10(-2)). The frequency of FDB in the sample of hypercholesterolemic subjects was 7/142, yielding a prevalence of approximately 1/190 extrapolated to the general population (90% confidence interval: 2.63 x 10(-3)-9.17 x 10(-2)). The combined prevalence based on both samples was 1/209. Thus, the investigated point mutation was highly prevalent in Switzerland and appeared to be more frequent than in other populations studied hitherto. Furthermore, the presence of the mutation was not necessarily associated with an elevation of serum cholesterol levels, particularly in young individuals. While in the non-affected volunteers cholesterol levels increased between the age of 19 and 23 years by 0.22 mmol/l or by 5.6% (P = 0.001), this phenomenon was even more pronounced in individuals with FDB. The three volunteers with the point mutation demonstrated an increase in total cholesterol concentrations by 1.30 mmol/l or by 25% within 2 years, suggesting that, in the early twenties, cholesterol concentrations increase markedly from normal to elevated levels. Considering the estimated high prevalence and the relative ease of PCR-based tests, screening for FDB may become a standard procedure in patients with suggested familial forms of hypercholesterolemia.

Adult↗
PubMed1993

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis for M(r) estimations of high-molecular-weight polypeptides.

A convenient method was established for the M(r) estimation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of large polypeptides in the range from 250,000 to 600,000. Such polypeptides had previously been shown to migrate improperly in various gel electrophoresis systems. In a conventional Laemmli system with 3% polyacrylamide, approximately linear log M(r) vs Rf plots could be obtained by varying the gel thickness which ranged from 0.4 to 1.5 mm. In the additional presence of an electrolyte, such as NaCl, running times were shorter and for evaluation linear plots could be constructed from runs in very thin gels with less than 0.5 mm thickness. Handling of gels was greatly facilitated by fixing them to one of the gel chamber glass plates via bind-silane treatment prior to casting.

Electrophoresis, Polyacrylamide Gel↗