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Biomedical subjects

K Mann

Publications and source records attributed to K Mann.

At least 145 records · Page 8Linked to original sources
PubMed2000

Primary malignant fibrous histiocytoma of the lung: IGF-II producing tumor induces fasting hypoglycemia.

Augmented glucose utilisation or secretion of insulin-like-growth-factor II (IGF-II) are discussed as important pathogenetic factors in tumor-associated hypoglycemia (Doege-Potter Syndrome) with suppressed insulin and C-peptide levels. Primary malignant fibrous histiocytoma of the lung is an uncommon neoplasia and its association with hypoglycemia is rare and the causal relationship remains unclear. - We report a 57-year-old male with spontaneous hypoglycemia (1.67 mmol/l) due to a primary malignant fibrous histiocytoma of the lung, secreting IGF-II. Insulin (0.10 nmol/l; normal range 0.33-1.2) and C-peptide (3.0 mIU/l; 5-25) levels were suppressed in combination with low levels of growth hormone (<0.5 ng/ml; <7 ng/ml) and IGF-I (<66.0 ng/ml; 70-246). The elevated IGF-II level (787 ng/ml; 300-500) and decreased IGF-binding protein 3 (1.6 mg/l; 2-5) indicated a high free IGF-II activity. After surgery (resection of the right upper lobe), glucose (4.4 mmol/l), insulin (9.0 mIU/L) and C-peptide (0.84 nmol/l) levels returned to normal. Serum IGF-I (289 ng/ml) and the IGF-I/IGF-II ratio (<0.08 preoperative vs. 0.41 postoperative; >0.20) increased to the normal reference range. - In conclusion, malignant fibrous histiocytoma (MFH) is rarely described presenting as tumor-induced hypoglycemia. Doege-Potter Syndrome in MFH seems to be related to tumor-associated IGF-II production.

Adult↗
PubMed2000

One hundred years of alcoholism: the Twentieth Century.

The past 100 years witnessed the formation of a disease concept of alcoholism and a rapid increase in the knowledge of its aetiopathology and treatment options. In the first half of the century, public sanctions aimed at the abolition of alcoholism. In the United States, alcohol prohibition was revoked in the economic turmoil of the Great Depression. In Germany, proposed medical procedures to reduce the fertility of alcoholics had catastrophic consequences during the fascist dictatorship. A revived focus on alcoholics as patients with a right to medical treatment came out of self-organized groups, such as Alcoholics Anonymous. The current disease concept includes the psychosocial and neurobiological foundations and consequences of alcoholism. Neurobiological research points to the dispositional factor of monoaminergic dysfunction and indicates that neuroadaptation and sensitization may play a role in the maintenance of addictive behaviour. New treatment options include pharmacological approaches and indicate that behaviour and motivational therapy and the attendance of patient groups may equally reduce the relapse risk. The task of the future will be to apply scientific discoveries in the best interest of the patients and to support their efforts to be respected like subjects suffering from other diseases.

Alcoholism↗
PubMed2000

Human sleep EEG under the influence of pulsed radio frequency electromagnetic fields. Results from polysomnographies using submaximal high power flux densities.

Former exploratory investigations of sleep alterations due to global system for mobile communications (GSM) signals have shown a hypnotic and REM-suppressive effect under field exposure. This effect was observed in a first study using a power flux density of 0.5 W/m(2), and the same trend occurred in a second study with a power flux density of 0.2 W/m(2). For the present study, we applied a submaximal power flux density of 50 W/m(2). To investigate putative effects of radio frequency electromagnetic fields (EMFs) of cellular GSM phones on human sleep EEG pattern, all-night polysomnographies of 20 healthy male subjects both with and without exposure to a circularly polarized EMF (900 MHz, pulsed with a frequency of 217 Hz, pulse duration 577 microseconds) were recorded. The results showed no significant effect of the field application either on conventional sleep parameters or on sleep EEG power spectra.

Adaptation, Physiological↗
PubMed2000

Time relationship between circadian variation of serum levels of leptin, insulin and cortisol in healthy subjects.

BACKGROUND: Leptin is involved in the regulation of eating behavior. Its serum levels are determined by fat mass but a diurnal rhythm is also described. It is not clear whether leptin levels are also controlled in vivo by hormonal stimuli, like insulin or cortisol. METHODS AND RESULTS: This possible temporal relation was investigated by serial measurements during 24 h (group A) and 46 h (group B) in 15 healthy volunteers and another 10 subjects (group C) while fasting for 72 h. Maximal leptin levels were observed at 4:00 a.m. and 4:00 p.m. in subjects on a normal diet. During 24 h starvation (group B), there was a 40% decrease of mean leptin concentration when compared to baseline values. In group C, the leptin concentration under starvation dropped to 25% of basal levels after 72 h. Pooled data from group A and the nonfasting data from group B showed an insulin increase preceding leptin increase by 6 h (r = 0.405, p < 0.0001), while cortisol decreased 4 h (r = 0.361, p < 0.001) after leptin decrease. CONCLUSION: Starvation results in a fall of circulating leptin, ending leptin rhythmicity. Food intake is causally involved in the fluctuation of leptin levels in serum. Presumably this effect is mediated by insulin, while cortisol does not seem to affect leptin release directly in vivo.

Circadian Rhythm↗
PubMed2000

Interaction between the cytodomains of the alpha 3 and beta 1 integrin subunits regulates remodelling of adhesion complexes on laminin.

The first step of laminin 1-induced signal transduction is initiated by the formation of alpha 6 beta 1 integrin-specific adhesion complexes. In contrast, on other laminin isoforms the adhesion complexes are alpha 3 beta 1 integrin-specific due to a transdominant regulation of the alpha 6 beta 1 integrin by the alpha 3 beta 1 integrin. To determine the mechanism of this regulation, peptides representing the cytoplasmic domain of the alpha 3 or alpha 6 integrin subunits were microinjected together with recombinant enhanced green fluorescence protein into live fibroblasts. Microinjection of the alpha 3 integrin peptide to laminin 1-adherent cells displaying alpha 6 beta 1 integrin-specific adhesion complexes resulted in the disengagement of the alpha 6 beta 1 integrin, while microinjection of green fluorescence protein alone or in combination with the alpha 6 integrin cytodomain had no effect. Further surface plasmon resonance studies revealed that the cytodomain of the beta 1 integrin subunit interacts with low affinity with the cytoplasmic tail of the alpha 3 integrin subunit, but not with that of several other alpha subunits including alpha 6. These results imply that the cytoplasmic tails of the integrin alpha subunits play a critical role in the regulation of integrin-induced signal transduction. In particular, the intracellular tail of the alpha 3 integrin subunit controls the formation of adhesion complexes in cells adhering to laminins.

Amino Acid Sequence↗
PubMed2000

Longitudinal changes of circadian leptin, insulin and cortisol plasma levels and their correlation during refeeding in patients with anorexia nervosa.

OBJECTIVE: To study the longitudinal changes in plasma levels of leptin, insulin and cortisol during the transition from the state of starvation to the state of refeeding focussing on diurnal secretion characteristics and their temporal relationships. DESIGN: Leptin, insulin and cortisol were measured every 2h for 24h during acute starvation (T1). Sampling was repeated after reaching half the target-body mass index (BMI) (T2) and again at target-BMI (17. 5kg/m(2); T3). The temporal relationships between the diurnal secretion patterns were assessed by cross-correlation analysis. RESULTS: Although BMIs at T1 were uniformly low, leptin levels varied widely within a range clearly below normal levels (0.03-1. 7microg/l). With increasing body fat during the course of refeeding, mean leptin levels increased from 0.64microg/l (range: 0.27-1. 73microg/l) (T1) to 1.61microg/l (range: 0.36-4.2microg/l) (T2) and to 3.67microg/l (range: 0.7-9.8microg/l) (T3). Circadian leptin secretion patterns showed maximal values uniformly around 0200h and minimal values around 0800h at all stages of the study. At all three weight levels, plasma leptin levels were highest between midnight and the early morning hours and lowest around the late morning hours. Refeeding neither profoundly changed secretion patterns of leptin nor did it change the positive, time-delayed relationship between leptin and insulin with increments in insulin secretion preceding those of leptin by 6h. A temporal relationship between leptin and cortisol could not be demonstrated in the state of semistarvation but emerged after a substantial weight gain; at that time, leptin increases preceded cortisol increases by 8h. CONCLUSIONS: Absolute leptin, insulin and cortisol levels are profoundly changed during starvation in anorectic patients, while refeeding, paralleled by a BMI gain, reverses these changes. During refeeding the relationship between leptin and cortisol changed profoundly, showing no significant correlation in the state of starvation, whereas at T3 after refeeding a strong inverse relationship could be observed. Leptin and insulin did not correlate significantly at any of the three stages studied.

Adult↗
PubMed2000

Sex differences of carbohydrate-deficient transferrin, gamma-glutamyltransferase, and mean corpuscular volume in alcohol-dependent patients.

BACKGROUND: Biological markers like carbohydrate-deficient transferrin (CDT), gamma-glutamyltransferase (GGT), and mean corpuscular volume (MCV) are used widely to screen for alcoholism. Most research has focused on male alcoholics, and there are few studies on female patients. The results are inconsistent; in general, they show lower sensitivities for all markers for women. METHODS: We compared the diagnostic value of CDT, GGT, and MCV in 126 alcohol-dependent patients (91 men, 35 women) who entered an inpatient treatment program. For the receiver operating characteristic (ROC) analyses, we investigated a control group of 112 patients (64 men, 38 women) from the Department of Psychiatry at the University of Tübingen with no diagnosis of substance abuse or substance dependency. RESULTS: Mean levels of CDT and MCV were significantly different in male and female patients. CDT showed higher test results in men (4.4% vs. 2.8%, p < 0.05), whereas mean levels of MCV were higher in women (99.7 fl vs. 96.4 fl,p < 0.01). The sensitivities of CDT and GGT were higher in men than in women (CDT: 76% vs. 54%,p < 0.1; GGT: 68% vs. 43%,p < 0.05), and the sensitivity of MCV was significantly higher in women (71% vs. 41%,p < 0.01). The superiority of MCV in women also was supported by ROC analyses (p < 0.01). The combined use of markers showed satisfactory sensitivity rates of > or = 80% not only in men but also in women. Yet, the specificity rates were partly below the recommended 90% for identifying alcohol abuse; therefore, these markers must be combined with caution. CONCLUSIONS: If combined, the biological markers CDT and GGT are useful diagnostic instruments for both alcohol-dependent men and women. According to our results, the "forgotten" marker MCV is superior in women and is a marker of second choice in men. The combination GGT and MCV is the most cost-effective choice for men and women.

Adult↗
PubMed1999

Isolation of a glycosylated form of the chicken eggshell protein ovocleidin and determination of the glycosylation site. Alternative glycosylation/phosphorylation at an N-glycosylation sequon.

Ovocleidin, a major protein of the avian eggshell calcified layer, occurs in the eggshell soluble organic matrix in at least two forms. The major form is a phosphoprotein with two phosphorylated serines (OC-17) which was sequenced recently. A minor form is a glycosylated protein with identical sequence and only one phosphorylated serine (OC-23). The site of glycosylation is Asn(59), the only asparagine in the amino acid sequence contained in the N-glycosylation site consensus sequence, N-A-S. Ser(61), which is part of this site, is phosphorylated in OC-17 but not in OC-23 indicating that the two modifications are mutually exclusive. This is the first example of alternative glycosylation/phosphorylation occurring at an N-glycosylation site.

Animals↗
PubMed1999

Cadmium induces conformational modifications of wild-type p53 and suppresses p53 response to DNA damage in cultured cells.

The p53 tumor suppressor protein is a transcription factor that binds DNA in a sequence-specific manner through a protein domain stabilized by the coordination of zinc within a tetrahedral cluster of three cysteine residues and one histidine residue. We show that cadmium, a metal that binds thiols with high affinity and substitutes for zinc in the cysteinyl clusters of many proteins, inhibits the binding of recombinant, purified murine p53 to DNA. In human breast cancer MCF7 cells (expressing wild-type p53), exposure to cadmium (5-40 microM) disrupts native (wild-type) p53 conformation, inhibits DNA binding, and down-regulates transcriptional activation of a reporter gene. Cadmium at 10-30 microM impairs the p53 induction in response to DNA-damaging agents such as actinomycin D, methylmethane sulfonate, and hydrogen peroxide. Exposure to cadmium at 20 microM also suppresses the p53-dependent cell cycle arrest in G(1) and G(2)/M phases induced by gamma-irradiation. These observations indicate that cadmium at subtoxic levels impairs p53 function by inducing conformational changes in the wild-type protein. There is evidence that cadmium is carcinogenic to humans, in particular for lung and prostate, and cadmium is known to accumulate in several organs. This inhibition of p53 function could play a role in cadmium carcinogenicity.

Animals↗
PubMed1999

Amino acid sequence, crystallization and structure determination of reduced and oxidized cytochrome c6 from the green alga Scenedesmus obliquus.

Cytochrome c6from the unicellular green alga Scenedesmus obliquus was sequenced, crystallized in its reduced and oxidized state and the three-dimensional structure of the protein in both redox states was determined by X-ray crystallography. Reduced cytochrome c6crystallized as a monomer in the space group P 21212, whereas the oxidized protein crystallized as a dimer in the space group P 3121. The structures were solved by molecular replacement and refined to 1. 9 and 2.0 A, respectively. Comparison of the structures of both redox states revealed only slight differences on the protein surface, whereas a distortion along the axis between the heme iron and its coordinating Met61 residue was observed. No redox-dependent movement of internal water molecules could be detected. The high degree of similarity of the surfaces and charge distributions of both redox states, as well as the dimerization of cytochrome c6as observed in the oxidized crystal, is discussed with respect to its biological relevance and its implications for the reaction mechanisms between cytochrome c6and its redox partners. The dimer of oxidized cytochrome c6may represent a molecular structure occurring in a binary complex with cytochrome b6f. This assembly might be required for the correct orientation of cytochrome c6with respect to its redox partner cytochrome b6f, facilitating the electron transfer within the complex. If the dimerization is not redox-dependent in vivo, the almost identical surfaces of both redox states do not support a long range differentiation between reduced and oxidized cyt c6, i.e. a random collision model for the formation of an electron transfer complex must be assumed.

Amino Acid Sequence↗
PubMed1999

Analysis of heparin, alpha-dystroglycan and sulfatide binding to the G domain of the laminin alpha1 chain by site-directed mutagenesis.

The 395-residue proteolytic fragment E3, which comprises the two most C-terminal LG modules of the mouse laminin alpha1 chain, was previously shown to contain major binding sites for heparin, alpha-dystroglycan and sulfatides. The same fragment (alpha1LG4-5) and its individual alpha1LG4 and alpha1LG5 modules have now been obtained by recombinant production in mammalian cells. These fragments were apparently folded into a native form, as shown by circular dichroism, electron microscopy and immunological assays. Fragment alpha1LG4-5 bound about five- to tenfold better to heparin, alpha-dystroglycan and sulfatides than E3. These binding activities could be exclusively localized to the alpha1LG4 module. Side-chain modifications and proteolysis demonstrated that Lys and Arg residues in the C-terminal region of alpha1LG4 are essential for heparin binding. This was confirmed by 14 single to triple point mutations, which identified three non-contiguous basic regions (positions 2766-2770, 2791-2793, 2819-2820) as contributing to both heparin and sulfatide binding. Two of these regions were also recognized by monoclonal antibodies which have previously been shown to inhibit heparin binding. The same three regions and a few additional basic residues also make major contributions to the binding of the cellular receptor alpha-dystroglycan, indicating a larger binding epitope. The data are also consistent with previous findings that heparin competes for alpha-dystroglycan binding.

Animals↗
PubMed1999

The intrinsic factor-vitamin B12 receptor, cubilin, is assembled into trimers via a coiled-coil alpha-helix.

A large protein was purified from bovine kidney, using selective extraction with EDTA to solubilize proteins anchored by divalent cation-dependent interactions. An antiserum raised against the purified protein labeled the apical cell surface of the epithelial cells in proximal tubules and the luminal surface of small intestine. Ten peptide sequences, derived from the protein, all matched the recently published sequences for rat (Moestrup, S. K., Kozyraki, R., Kristiansen, M., Kaysen, J. H., Holm Rasmussen, H., Brault, D., Pontillon, F., Goda, F. O., Christensen, E. I., Hammond, T. G., and Verroust, P. J. (1998) J. Biol. Chem. 273, 5235-5242) and human cubilin, a receptor for intrinsic factor-vitamin B12 complexes, identifying the protein as bovine cubilin. In electron microscopy, a three-armed structure was seen, indicating an oligomerization of three identical subunits. This model was supported by the Mr values of about 1,500,000 for the intact protein and 440,000 for its subunits obtained by analytical ultracentrifugation. In a search for a potential assembly domain, we identified a region of heptad repeats in the N-terminal part of the cubilin sequence. Computer-assisted analysis supported the presence of a coiled-coil alpha-helix between amino acids 103 and 132 of the human cubilin sequence and predicted the formation of a triple coiled-coil. We therefore conclude that cubilin forms a noncovalent trimer of identical subunits connected by an N-terminal coiled-coil alpha-helix.

Amino Acid Sequence↗
PubMed1999

Unique alterations of thyroid function parameters after i.v. administration of alkylating drugs (cyclophosphamide and ifosfamide).

Alkylating drugs (cyclophosphamide and ifosfamide) have been in clinical use for the treatment of malignant diseases in the past. They are most useful anticancer agents and cyclophosphamide is also widely used for its immunosuppressive properties. However the effect of alkylating drugs on thyroid hormone parameters have not been evaluated so far. Three groups of patients were prospectively evaluated: Group I: 15 patients with Wegener's granulomatosis and 4 patients with severe scleritis received a single dose cyclophosphamide (15 mg/kg bw/day) and 250 mg prednisone i.v. Group II: 9 patients with malignant lymphomas were treated according to the IMVP 16-protocol. Patients received daily ifosfamide 1000 mg/m2 from day 0 to 4 and vepesid from day 0 to 2. Patients did not receive corticosteroids additionally. Group III: 6 patients with a relapse of malignant lymphomas received ifosfamide 1.500 mg/m2/day from day 0 to 4 i.v. and dexamethasone 40 mg/m2 as well as ara-c and etoposid. All patients received mesna to prevent hemorrhagic cystitis and odansetran or metoclopramide as antiemetic drugs. Alkylating drugs were given as a one hour infusion. Thyroid hormone parameters were determined before and on day 1, 2, 3, 4 after drug administration. We observed a significant increase in T4 and fT4 concentrations and a concomitant fall in TSH in either group one day after the administration of alkylating drugs. The effect was most pronounced in group III: T4 increased from 113 +/- 8 nmol/L to 175 +/- 8 (normal: 58-154) and fT4 from 14.0 +/- 0.8 to 24.8 +/- 2.5 pmol/L (normal 10-25). TSH dropped from 1.27 +/- 0.16 to 0.33 +/- 0.07 mU/L (normal 0.3-4). All changes were significant: p < 0.001. Two of the six patients displayed biochemical hyperthyroidism. Also reverse T3 increased significantly. Two days after drug administration a gradual normalization occurred. However, T3, Tg, TBG, Transthyretin and albumin levels did not change throughout the study period. One patient with coexisting hypothyroidism, who received his last thyroxine substitution therapy one day before the administration of cyclophosphamide (as in group I), also demonstrated an increase in T4, fT4 and rT3 and a fall in TSH concentrations. I.v. administrations of cyclophosphamide and ifosfamide induce a transient increase in T4 and fT4 concentrations and a concomitant fall of TSH in the presence of normal Tg, T3 and thyroid binding protein concentrations. These data suggest, that the changes are not due to a release of thyroid hormones from the thyroid itself, but is likewise related to a release of thyroxine from cellular pools such as the liver.

Adult↗
PubMed1999

Risk of smoking in thyroid-associated orbitopathy.

Cigarette smoking greatly increases the risk of thyroid-associated orbitopathy (TAO) (odds ratio 7.7, interval 4.3 to 13.7) and the number of cigarettes smoked per day seems to be a significant independent determinant for the incidence of proptosis and diplopia. The own prospective study showed that soft tissue involvement (ATA activity score) and ocular motility could be influenced less by steroid and irradiation treatment in smokers in comparison to nonsmokers. The mechanisms whereby smoking affects eye disease are widely unknown, cytokines (INF-gamma, TNF-alpha, IL-1), receptors and receptor antagonists have probably a crucial role.

Graves Disease↗
PubMed1999

Bone loss in patients with inflammatory bowel disease is less than expected: a follow-up study.

BACKGROUND: In spite of the accumulating evidence of an increased prevalence of osteopenia and osteoporosis in patients with inflammatory bowel diseases (IBD), the time course of bone loss is not well described, and there is little knowledge about factors indicating an increased risk of rapid bone loss. METHODS: We conducted a follow-up study in 80 IBD patients (45 men and 25 premenopausal and 10 postmenopausal women), 19 with ulcerative colitis and 61 with Crohn disease, with a mean follow-up time of 568 +/- 60 days, to assess bone loss, risk factors of rapid bone loss, and value of bone markers to predict bone loss. Bone mineral density was measured by dual-energy X-ray absorptiometry, bone formation by bone alkaline phosphatase (BAP), and bone resorption by N-terminal telopeptide of type-I collagen (NTX) and free deoxypyridinoline (DPD). RESULTS: Bone density changes per year were 0.46% +/- 3% at the spine, 0.06% +/- 5.1% at the femoral neck, -1.1% +/- 7.7% at the triangle of Ward, and -0.52% +/- 1.86% at total body level. Type and duration of disease, sex, age, and level of NTX, DPD, and BAP at base line did not show significant differences between patients who lost and those who did not lose bone mass. Bone loss was significantly higher in patients with (n = 28) than in those without steroids (n = 52) at the femoral neck and Ward triangle but not at the spine and total body. CONCLUSIONS: Change in bone mass in IBD patients during short-term follow-up is low on average, but there is great heterogeneity within the population, which cannot be explained by the use of steroids alone. Bone loss cannot be predicted by analysis of bone markers.

Adult↗