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Biomedical subjects

K Mann

Publications and source records attributed to K Mann.

At least 217 records · Page 12Linked to original sources
PubMed1997

Non-linear dynamics of alpha and theta rhythm: correlation dimensions and Lyapunov exponents from healthy subject's spontaneous EEG.

The aim of the present paper was to analyze some non-linear dynamic properties of the resting EEG from healthy subjects under eyes closed conditions. For this purpose we digitally filtered the spontaneous EEG in the theta (3-8 Hz) and alpha frequency range (8-13 Hz) and considered these independent rhythms as signals from a deterministic system. Under certain conditions non-linear dynamic systems are able to generate deterministic chaos, which means that similar causes do not produce similar effects. This phenomenon is called sensitive dependence on initial conditions. From different lead positions (F3, F4, Cz, P3, P4, O1 and O2) we calculated the so-called correlation dimension D2, which is assumed to be an estimation of the system's complexity, and the Lyapunov exponent L, which appears to be a measure of the sensitive dependence on initial conditions. Our investigations revealed that the dimensionality of the theta- and alpha-rhythm varies within subjects across the experimental session in wide ranges. The degrees of freedom of the alpha and theta rhythms across the scalp are in the same order, indicating dynamic processes which can not be differentiated by applying the Grassberger-Procaccia algorithm. The Lyapunov-exponents, indicating 'how chaotic a deterministic process is', are in general smaller for the theta than for the alpha activity. Across the scalp there is no evidence for different dynamics of the theta rhythm. The dynamics of the alpha rhythm, on the contrary, appears to be different at various lead positions. It appears justified to state that the dynamics of the frontal alpha activity is functionally different from the alpha activity recorded at other topographic locations.

Algorithms↗
PubMed1997

Triiodothyronine (T3) reflects renal graft function after renal transplantation.

OBJECTIVE: Abnormalities in thyroid function are observed in patients with end stage renal disease. However, there are no data available evaluating sequential changes of thyroid function after renal transplantation. Therefore, we have studied thyroid hormone function in the immediate post-operative period after renal transplantation in order to determine the relationship between improving renal function and changes in thyroid hormone economy. DESIGN AND PATIENTS: Thyroid function was evaluated in 22 patients before and on days 1, 3, 7 and 15 after renal transplantation. All patients received prednisone and cyclosporin as immunosuppressive therapy. Twelve patients with normal renal function undergoing comparable surgical procedures served as a control group. MEASUREMENTS: Serum creatinine and thyroid hormone parameters (total T4, total T3, free T4, free T3, thyroxin binding globulin (TBG), reverse T3, T3 sulphate and TSH) were measured. RESULTS: According to post-operative kidney function after renal transplantation, patients could be subdivided into three groups: five patients had primary graft function (group I); seven patients had delayed graft function because of acute renal failure (group II); 10 patients had delayed graft function requiring high doses of prednisone and some also of OKT3 because of acute rejection (group III). There was a significant fall in T3 and T4 concentrations with a concomitant rise in reverse T3 in all patients up to 3 days after renal transplantation. However, only patients in group I reached pre-operative values on day 15 after renal transplantation (serum creatinine 167 +/- 52 microM), whereas patients in group II (creatinine 609 +/- 118 microM) and group III (creatinine 839 +/- 71 microM) continued to have T3 concentrations well in the hypothyroid range (group I, 1.68 +/- 0.28 nM) vs 0.87 +/- 0.09 nM in group II and 0.76 +/- 0.10 nM in group III; P < 0.01). Serum T4 concentrations were also low in group III (47.7 nM vs 100.2 nM in group I; P < 0.05) 15 days after renal transplantation. These changes were accompanied by a concomitant fall in T3/TBG ratio and in free T3. Elevated reverse T3 returned to normal values in all groups on the 15th day after renal transplantation. TSH fell significantly on the first post-operative day, but did not return to pre-operative values in renal transplantation patients. In the control group, TSH did not change during the study period. T3 sulphate, known to be elevated in chronic renal failure, remained above normal in all patients irrespective of graft function during this study period. CONCLUSIONS: T3 concentrations reflect renal graft function after renal transplantation. T3 is below normal in patients with delayed graft function (acute renal failure or acute rejection). The post-operative period (up to 3 days after renal transplantation) is associated with a low T3 syndrome. TSH does not return to pre-operative values even in patients with primary graft function. This might be due to the administration of prednisone. T3-sulphate is elevated before and after renal transplantation irrespective of graft function.

Acute Kidney Injury↗
PubMed1997

Different phase relationships between EEG frequency bands during NREM and REM sleep.

Phase relationships between distinct frequency bands of the sleep electroencephalogram (EEG) were studied in healthy subjects using cross-correlation coefficients, both over the entire night and separately for nonrapid eye movement (NREM) and rapid eye movement (REM) sleep. Over the entire night, a large positive correlation developed within high- and low-frequency bands, while a negative correlation emerged between low- and high-frequency bands, reflecting their reciprocal temporal course. More detailed analysis revealed different phase relationships during NREM and REM sleep. Findings during NREM were similar to the entire night. However, during REM, a large increase of the correlation between low- and high-frequency bands occurred compared to NREM, even with a change of sign. The results indicate the complexity of the interrelation of the different frequency bands depending on sleep state, with low- and high-frequency bands being out of phase during NREM and in phase during REM sleep.

Adult↗
PubMed1997

Influence of coronary artery bypass surgery on thyroid hormone parameters.

UNLABELLED: The postoperative period after cardiac surgery with cardiopulmonary bypass (CPB) is associated with a low T3 syndrome, i.e. low T3 and fT3 concentrations in the presence of normal T4 and TSH concentrations. So far, results from studies evaluating thyroid function during and after CPB are rather conflicting. We therefore evaluated prospectively thyroid function in 28 patients before, during and up to 3 days after coronary artery bypass surgery. We could demonstrate the most significant changes in thyroid hormone concentrations on day 1 after CPB (low T3 and fT3 concentrations, elevated rT3 concentrations in the presence of a significant fall of TSH). T3 fell from 1.93 to 0.6 nmol/1 and fT3 from 5.5 to 1.42 pmol/1. Those patients with low cardiac output syndrome after surgery had significantly lower T3 concentrations than patients without this complication. Moreover, those patients, who already had significant lower T3 values prior to CPB, also demonstrated low T3 concentrations on day 1 after CPB. Cortisol usually has a suppressive effect on TSH secretion. However, the effect of cortisol on TSH in patients undergoing CPB seems to be not that important: those patients with high endogenous cortisol concentrations on day 1 after CPB had similar TSH values to those patients with only slightly elevated cortisol concentrations. Also, the application of high doses of catecholamines seems to have only minor effects on TSH secretion, because those patients requiring high doses of dopamine over a prolonged time period had essentially the same TSH values after CPB. Patients who had been exposed preoperatively to high doses of iodine did not demonstrate significantly different thyroid hormone concentrations. IN CONCLUSION: We could demonstrate that CPB induces a low T3 syndrome up to 3 days after surgery. Those patients with low T3 concentrations prior to surgery demonstrate postoperatively a more severe degree of nonthyroidal illness (NTI). Catecholamines and cortisol seem to have only minor effects on the TSH secretion after CPB. The influence of a previous iodine contamination is negligible.

Aged↗
PubMed1997

Regulation of intercellular adhesion molecule-1 expression in human thyroid cells in vitro and human thyroid tissue transplanted to the nude mouse in vivo: role of Graves' immunoglobulins and human thyrotropin receptor.

To further explore a potential role for the human TSH receptor (hTSHR) in the propagation of thyroid autoimmune disease, we examined immunomodulatory effects in response to its stimulation by Graves' Igs both in human thyroid tissue transplanted to the nude mouse and in primary cultures of human thyrocytes. We injected nude mice bearing transplants derived from normal human thyroid with protein A-Sepharose-purified Graves' IgGs (0.05-1 mg) on 2 days and assessed, in addition to functional stimulation, the expression of intercellular adhesion molecule-1 (ICAM-1) by transplant thyrocytes. In parallel to functional stimulation, as demonstrated by thyroid follicular cell hypertrophy in the transplants and increased T4 production, Graves' IgGs induced a marked dose-dependent expression of ICAM-1 by transplanted thyrocytes, which exceeded that of a continuous interferon-gamma infusion (200 IU/24 h) for 2 days. Normal IgGs were ineffective. Bovine TSH (bTSH) had little effect by itself, but did enhance interferon-gamma-induced ICAM-1 expression. To assess the specificity of their effects, experiments with Graves' IgGs were conducted in the presence and absence of a selective hTSHR antagonist (asialoagalacto-hCG). Asialoagalacto-hCG nearly completely abolished the stimulatory effect of Graves' IgGs on ICAM-1 expression and significantly reduced the combined bTSH/interferon-gamma effect. It failed, however, to affect interferon-gamma action. In vitro studies using human thyroid cells in primary culture confirmed the in vivo observations, treatment with saline resulted in 14% of cells expressing ICAM-1, with pooled normal IgGs (500 mg/L) in 18% and with Graves' IgGs (patient A, 448 mg/L; patient B, 260 mg/L) in 78% and 51%, respectively. Upon exposure to Graves' IgGs (90 mg/L) plus asialo-hCG(350 mg/L), 25% of the cells stained positively for ICAM-1, 29% to bTSH (10 IU/L), 31% to recombinant human TSH (10 IU/L), and 84% to interferon-gamma (10 IU/mL). In conclusion, stimulation of human thyroid cells, either transplanted to the nude mouse in vivo or studied under in vitro conditions, with Igs derived from patients with Graves' disease increased the expression of ICAM-1 on the surface of the cells. The action appears to be specific and mediated by the hTSHR. This particular property of TSHR autoantibodies may be of pathophysiological relevance in Graves' disease, as it may assist in targeting the autoimmune attack and in promoting lymphocyte recruitment to the thyroid gland.

Animals↗
PubMed1997

Association between visual reaction time and batting, fielding, and earned run averages among players of the Southern Baseball League.

BACKGROUND: This study was performed to investigate the relationship between vision reaction time (VRT) and batting, fielding, and pitching skill in baseball. METHODS: A vision screening of 213 professional baseball players in the Southern Baseball League was performed, and the visual reaction times of these players were determined. Official Southern Baseball League statistics were consulted to obtain the players' batting average, fielding average, and earned run average. RESULTS: The mean visual reaction time for all players was 239 msec. There was no significant association between mean VRT and age or race. The mean VRT for dominant eyes was not significantly different from the mean VRT for nondominant eyes. For the 92 players who batted at least 100 times, an association was found between mean VRT and batting average (p = 0.017). For the 168 fielders in the league playing at least 20 games, no statistically significant association was found between mean VRT and fielding average. Similarly, no association was found between mean VRT and earned run average for the B8 pitchers who had participated in more than 20 games. CONCLUSIONS: An association was found between visual reaction time and batting skill in baseball. No association was found between visual reaction time and fielding or pitching skill.

Baseball↗
PubMed1997

No short-term effects of digital mobile radio telephone on the awake human electroencephalogram.

A recent study reported the results of an exploratory study of alterations of the quantitative sleep profile due to the effects of a digital mobile radio telephone. Rapid eye movement (REM) was suppressed, and the spectral power density in the 8-13 Hz frequency range during REM sleep was altered. The aim of the present study was to illuminate the influence of digital mobile radio telephone on the awake electroencephalogram (EEG) of healthy subjects. For this purpose, we investigated 34 male subjects in a single-blind cross-over design experiment by measuring spontaneous EEGs under closed-eyes condition from scalp positions C3 and C4 and comparing the effects of an active (0.05 mW/cm2) and an inactive digital mobile radio telephone (GSM) system. During exposure of nearly 3.5 min to the 900 MHz electromagnetic field pulsed at a frequency of 217 Hz and with a pulse width of 580 microseconds, we could not detect any difference in the awake EEGs in terms of spectral power density measures.

Adult↗
PubMed1997

[Clinical aspects and preoperative diagnosis in differentiated thyroid gland carcinoma].

Etiologic factors such as iodine deficiency and exposure to ionizing radiation especially during childhood are determinants of histological type and malignancy of differentiated thyroid carcinomas. The rarely occurring anaplastic thyroid carcinoma represents a highly malignant tumour of old patients, causing local compression symptoms at an early stage of disorder. Since early symptoms are lacking, sensitivity and specificity of further diagnostic approaches are of particular importance in the care of differentiated thyroid carcinomas. Obligatory procedures at the preoperative stage are ultrasound, scintigraphy, determinations of thyroid hormones and calcium on serum as well as an otolaryngological investigation. The preoperative determination of calcitonin may assist in the differential diagnosis of a cold nodule and in the detection of a medullary thyroid carcinoma. Measurements of thyroglobulin are helpful only for the follow-up of patients with differentiated carcinomas. The highest degree of specificity and sensitivity is achieved by fine-needle aspiration. Finally, if clinical suspicion of malignancy exists, surgical intervention should be performed even if the result of cytological analysis was negative. Whether the color Doppler energy ultrasound provides valuable additional informations especially in the differential diagnosis of thyroid nodules during childhood, is still undecided.

Adenocarcinoma, Follicular↗
PubMed1997

The value of tumor markers in testicular seminomas. Results of a prospective multicenter study.

OBJECTIVES: In the course of a prospective multicenter trial, the value of tumor markers in seminomas was assessed. METHODS: Human chorionic gonadotropin (HCG), lactate dehydrogenase (LDH) and placental alkaline phosphatase (PlAP) were determined before and after orchidectomy and in the follow-up. Patients with elevated alpha-fetoprotein were considered to have nonseminomas. The half-lives were 24-36 h for HCG and 1 day for LDH and PlAP. RESULTS: The incidence of HCG, LDH and PlAP was 35, 34 and 56%, respectively. In 84% of the patients at least one of the three markers was elevated. PlAP had the highest sensitivity to detect metastatic disease (51%), with a specificity of 91%. HCG and LDH were elevated in 42 and 46% of patients in stage II-III with specificities of 95 and 96%. PlAP was the best method to indicate a relapse, but the specificity was low, especially in smokers. For nonsmokers it was in the same range as HCG and LDH. CONCLUSIONS: Eighty-four percent of seminomas are marker-positive. PlAP has the highest incidence and sensitivity. Specificity is impaired in smokers. All three markers should be determined in seminomas.

Alkaline Phosphatase↗
PubMed1997

[Thyroid hormone resistance: variable clinical manifestations in five patients].

AIM: The syndrome of thyroid hormone resistance (RTH) is characterised by elevated circulating thyroid hormones, unsuppressed TSH levels and peripheral refractoriness to hormone action. Patients with RTH may be clinically hyperthyroid if the pituitary gland is more insensitive than other tissues to thyroid hormones. More often, patients have peripheral tissue resistance as well and are euthyroid. RTH is related to point mutations in the T3-binding domain of the beta-receptor gene. We report the variable clinical and biochemical features of five patients with RTH. METHODS: Five patients with RTH were clinically and biochemically evaluated: thyroid tests were done at baseline, after TRH stimulation and after T3-suppression test. Thyroid ultrasound was performed as well. Individual exons of the thyroid hormone receptor beta gene were amplified from leucocyte DNA in these patients using the polymerase chain reaction (PCR). RESULTS: Sequence analysis identified a single point mutation at a certain nucleotide position. This corresponds to aminoacids substitutions at one position in the predicted aminoacid sequence. RTH was familial in three individuals and sporadic in two. Three of the patients underwent thyroid surgery or radioiodine treatment because of recurrent goiter and/or "refractory hyperthyroidism". Moreover, one of our patients with RTH developed also hyperthyroidism due to Graves disease and underwent thyroid surgery for the third time. Her brother, besides RTH, demonstrated strongly positive TPO-antibodies and a hypoechogenic pattern on ultrasound. So the diagnosis of Hashimoto's thyroiditis was made. CONCLUSIONS: RTH has to be considered in all patients with inappropriate TSH secretion. The clinical manifestation of patients with RTH is heterogenous. Thyroid antibody measurements should be performed regularly in order to detect the development of coexisting autoimmune thyroid disease.

Adult↗
PubMed1997

[Do low-threshold detoxification units reach new groups of the drug dependent?].

The conventional form of detoxication for illicit drug users in German psychiatric hospitals is an inpatient treatment approach connected with high admission prerequisites. These demand a high stage of motivational compliance from of the patients, e.g. the determination to continue with long-term treatment aiming at a life free of drugs. This strategy is termed "high-threshold" approach. A new form of inpatient treatment is the "low-threshold" approach offering intervals of some days or weeks free of drugs to illicit drug users, supported by professional detoxication strategies. This study compares client characteristics of illicit drug users treated at "high-threshold" vs. "low-threshold" units. A new subpopulation of clients could be reached who are more advanced in their drug intake careers and less influenced by social pressure to enter treatment. The differences in clients treated can be explained rather by differences in admission prerequisites than by a more balanced distribution of sexes in the newly introduced detoxication programme.

Adult↗
PubMed1997

Insights from a nursing research program on social support.

This paper highlights the conceptual and practical implications of a nursing research program that focuses on social support. The diverse dimensions of the construct of social support; its relationship to stress and coping; and its impact on health, health behaviour, and use of health services are explicated in the conceptual framework underpinning the program. These associations will be elucidated by citing examples from eight assessment studies and four intervention studies. The research program yielded new insights and reinforced reported findings of other social-support research.

Adaptation, Psychological↗
PubMed1996

Immunochemical mapping of gonadotropins.

As a glycoprotein hormone, human chorionic gonadotropic (hCG) is not a single molecular entity but this term rather comprises an array of molecular variants such as hCG, hCG beta, hCGn, hCG beta n, hCG beta cf, -CTPhCG, hCG beta CTP, deglyhCG, asialohCG, hCGav and the closely related molecules hLH, hLH beta and hLH beta ef. The advent of monoclonal antibodies (MCA), the availability of ultrasensitive detection systems and the recent determination of the crystal structure of hCG, made it possible to design special purpose diagnostic and clinical research immunoassays for hCG-like molecules. For more than a decade we and others have tried to refine epitope maps for hCG and related molecules by means of a large panel of MCA, naturally occurring metabolic variants of hCG (hCGn, hCG beta, hCG alpha, hCG beta cf, hCG beta CTP), homologous hormones and subunits of various species (e.g. hLH, hLH beta, hFSH, hTSH, oLH, rLH beta), chemically modified molecules (deglyhCG, asialohCG, tryptic and chymotryptic hCG beta and hCG alpha fragments) and synthetic peptides (octapeptides and longer). It appeared that all epitopes on molecular hCG-variants recognized by our MCA are determined by the protein backbone. Except for the two major epitopes on hCG beta CTP and parts of two antigenic domains on hCG alpha, epitopes on hCG-derived molecules are determined by the tertiary and quarternary structure. Operationally useful descriptive epitope maps were designed including information on assay suitability of antigenic determinants. On this basis we established ultrasensitive time-resolved fluoroimmuno-assays for hCG, hCG and hCGn, hCG beta and hCG beta n and hCG beta cf, hCG alpha and additional assays recognizing different spectra of hCG-variants. Such assay have been applied by us and others to the detection of pregnancy, early pregnancy loss, choriocarcinoma, testicular cancer, other cancers and prenatal diagnosis. However, as the molecular structure of many epitopes utilized in immunoassays of different laboratories was not resolved, comparability of results was not satisfactory. Consequently, attempts were made to compare schematic epitope maps from different research institutions. The situation has been much improved by solving the three-dimensional (3D) structure of hCG. It has been shown that hCG is a member of the structural superfamily of cystine knot growth factors like NGF, PDGF-B and TGF-beta. Each of its subunits is stabilized in its topology by three disulfide bonds forming a cystine knot. Moreover, it turned out that the disulfide bridges in their majority have previously been wrongly assigned. Computer molecular modeling of crystallographic coordinates of hCG and subsequent selective combined--PCR-based and immunological--mutational analyses of hCG beta expressed via the transmembrane region of a MHC molecule made it possible to more precisely localize epitopes on hCG-derived molecules. Although the entire surface of hCG has to be regarded as potentially immunogenic there seems to be hot spots where epitopes are clustered in antigenic domains. These are located on the first and third loops protuding from the cystine knots of both subunits and are possibly centered around the knot itself. Ultimate answers on epitope localizations will be given by the crystal structure determination of hCG complexed with different Fabs.

Amino Acid Sequence↗
PubMed1996

Primary structure of stallion seminal plasma protein HSP-7, a zona-pellucida-binding protein of the spermadhesin family.

The primary-structure of HSP-7, a 14-kDa protein isolated from stallion seminal plasma, has been determined, HSP-7 belongs to the spermadhesin protein family, shares 98% sequence identity with the boar seminal plasma protein AWN, and, like its boar homolog, displays zona-pellucida-binding activity. Despite these conserved structural and functional features, the equine and porcine spermadhesins differ in their topography on spermatozoa.

Amino Acid Sequence↗
PubMed1996

The primary structure of BSP-30K, a major lipid-, gelatin-, and heparin-binding glycoprotein of bovine seminal plasma.

BSP-30K is a major acidic glycoprotein of bovine seminal plasma. It displays heparin-, gelatin-, and phospholipid-binding activities. BSP-30K binds to spermatozoa upon ejaculation and is thought to play a role in sperm capacitation. We have determined its amino acid sequence, disulfide bonds, and 0-glycosylation sites. BSP-30K consists of 158 amino acids arranged in a mosaic structure. BSP-30K has a unique 48-residue N-terminal extension which includes three 7-8- amino acid repeats and the six O-glycosylated threonine residues. The polypeptide stretch 49-71 is homologous to type 'A' domains found in heparin-binding proteins from other mammalian species. The C-terminal portion of BSP-30K is organized in a tandem of 40-44-residue domains each sharing the consensus pattern of the gelatin-binding fibronectin type II module. The mosaic structure of BSP-30K suggests that this glycoprotein might be a factor contributing to the different sperm-capacitating effects exerted by heparin in different mammalian species.

Amino Acid Sequence↗
PubMed1996

The recognition sites of the integrins alpha1beta1 and alpha2beta1 within collagen IV are protected against gelatinase A attack in the native protein.

The susceptibility of three different solubilized forms of type IV collagen to gelatinase A cleavage and the concomitant effects on cell and integrin binding have been assessed. Dithiothreitol-solubilized Engelbreth-Holm Swarm (EHS) type IV collagen with disrupted intramolecular disulfide bonds in the CB3[IV] region was cleaved N-terminally to the CB3[IV] region into the two characteristic 100-300-nm fragments at 30 degrees C and was totally degraded at 37 degrees C. This was reflected in the partial or total loss of the alpha1beta1 and alpha2beta1 integrin binding sites within this region. The ability of gelatinase A to cleave EHS type IV collagen preparations with intact interchain disulfide bonds in CB3[IV] only occurred at higher temperatures. Furthermore, no effect on binding of cells or isolated integrins to the gelatinase-treated collagen could be detected after treatment at 37 degrees C. Dimeric collagen IV of human placenta with intact disulfide bonds in the CB3[IV] region was not degraded at all by gelatinase A at 37 degrees C.

Amino Acid Sequence↗
PubMed1996

Structural characterization of recombinant domain II of the basement membrane proteoglycan perlecan.

Mouse perlecan domain II (325 residues), consisting of four cysteine-rich LA modules, one IG module and a link region, was obtained in purified form from a stably transfected mammalian cell clone. Rotary shadowing electron microscopy demonstrated a globular domain connected to a short rod-like segment of variable length. This suggested that tandem arrays of LA modules form rod-like elements. Folding into a native structure was indicated by the sharing of immunological epitopes with tissue perlecan, a CD spectrum demonstrating 37% beta structure and a limited susceptibility to proteolysis. The domain also showed N-glycosylation of a single acceptor site and 7-8 O-linked oligosaccharides. The latter were located mainly in the link region within proline-rich sequences.

Amino Acid Sequence↗