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Biomedical subjects

J Neumann

Publications and source records attributed to J Neumann.

At least 55 records · Page 3Linked to original sources
PubMed1994

TP53 alterations and clinical outcome in low grade astrocytomas.

Thirty-eight WHO grade II astrocytomas and 10 malignant recurrent gliomas in these patients were examined for the presence of TP53 alterations. Seventeen/38 low grade astrocytomas and 6/10 malignant recurrent tumors harbored mutations of the gene detected by SSCP analysis and direct sequencing of PCR products. TP53 mutations in five out of six high grade mutant tumors were already present in the corresponding low grade astrocytomas. In two cases, TP53 mutations present in the low grade astrocytoma could not be demonstrated in the recurrent glioma. Immunohistochemistry with two different antibodies to the human TP53 protein revealed nuclear immunoreaction of tumor cells in 11/38 low grade and in 8/10 recurrent tumors. There was no correlation between the presence of TP53 alteration and clinical course. We conclude that, although TP53 mutations are detectable in a substantial fraction of WHO grade II astrocytomas, they do not appear to play a role in the malignant progression of these tumors and they are not of prognostic significance.

Amino Acid Sequence↗
PubMed1994

Chirp evoked otoacoustic emissions.

The principles of short frequency sweeps (chirps) and their application to evoke transiently evoked otoacoustic emissions (TEOAE) are developed in comparison to using standard click stimuli. In contrast to click stimuli, chirp signals have the advantage of stimulating a freely selectable frequency range. In addition, chirp signals contain more energy than a click stimulus with the same maximum amplitude. The effects of different stimuli on TEOAE were investigated in normal hearing and hearing-impaired subjects. Using wide-band chirp signals yields a better signal-to-noise ratio compared to click stimulation. In addition, the stimulation of selected regions of the basilar membrane with frequency-limited chirps evokes TEOAE with frequency components that lie within the stimulated frequency range. The characteristic fine structure of this spectrum was found to be independent of the stimulus applied. The utilization of chirp stimuli appears to be useful for evoking TEOAE in, e.g., clinical applications.

Acoustic Stimulation↗
PubMed1994

M2-specific muscarinic cholinergic receptor-mediated inhibition of cardiac regulatory protein phosphorylation.

Acetylcholine acting via muscarinic cholinoceptors decreased phosphorylation of phospholamban and troponin I without reducing adenosine 3',5'-cyclic monophosphate (cAMP) levels or cAMP-dependent protein kinase activity ratio in the presence of 10-100 nM isoproterenol in guinea pig ventricular myocytes. The effect of acetylcholine was more pronounced when adenosine deaminase (5 U/ml) was present and incubation period was short (10 s). Okadaic acid, an inhibitor of protein phosphatase activity, blocked the acetylcholine-mediated inhibition of isoproterenol-stimulated phosphorylation of phospholamban. It is suggested that acetylcholine reduces protein phosphorylation by a cAMP-independent mechanism in guinea pig ventricular myocytes.

Acetylcholine↗
PubMed1994

Biochemical and electrophysiological mechanisms of the positive inotropic effect of calyculin A, a protein phosphatase inhibitor.

Calyculin A (CyA; 1 microM) increased the force of contraction in isolated guinea pig papillary muscles to 144% of control without affecting contraction parameters. The effect of CyA on L-type calcium channels was assessed in cell-attached patches of guinea pig ventricular cardiomyocytes. Unitary Ba++ current recordings revealed that CyA at micromolar concentrations enhanced channel availability almost 2-fold, whereas the duration of individual openings and closures remained unchanged. In whole-cell recordings with Ca++ as the charge carrier, intracellular dialysis of 1 microM CyA enhanced peak current to a similar extent. In homogenates from guinea pig ventricles, 1 microM CyA completely inhibited phosphorylase phosphatase activity. In isolated [32P]-labeled guinea pig ventricular cardiomyocytes, 1 microM CyA increased the phosphorylation state of phospholamban (to 267% of control), that of the inhibitory subunit of troponin (to 182% of control) and those of various additional proteins. We conclude that the effects of CyA are likely to be mediated by increasing the phosphorylation state of several regulatory proteins.

Animals↗
PubMed1994

[Primary and secondary interventions--a concept in surgical documentation].

Nowadays systematic documentation of surgical procedures is absolutely necessary in all departments of surgery and will soon be required by law. Therefore code systems are essential. Amongst numerous systems the ICPM-GE classification has been chosen as basis. In the department for abdominal and transplantation surgery at Hanover Medical School the ICPM-GE classification has been extended by a concept of coding main and suboperations. This concept considers the fact that in an individual patient the surgical procedure may consist of different and standardized suboperations. This concept widens and simplifies the possibility of documentation considerably.

Cholecystectomy↗
PubMed1994

Effects of adenosine receptor and muscarinic cholinergic receptor agonists on cardiac protein phosphorylation. Influence of pertussis toxin.

In isolated 32P-labeled guinea pig ventricular cardiomyocytes phospholamban (PLB), myosin light chain 2 and the inhibitory subunit of troponin (Tnl) were identified by antibodies. In isolated 32P-labeled guinea pig ventricular cardiomyocytes isoproterenol (0.1 mumol/l) increased phosphorylation of PLB and of the inhibitory subunit of Tnl to 159 and 119% of control, respectively, without effect on the phosphorylation state of myosin light chain 2. Additionally applied carbachol or (-)-N6-phenylisopropyladenosine reduced phosphorylation of PLB and Tnl without reducing cyclic AMP content. After pretreatment of guinea pigs with pertussis toxin (18 micrograms/100 g b.wt.), carbachol or (-)-N6-phenylisopropyladenosine failed to reduce isoproterenol-stimulated phosphorylation of both PLB and Tnl. It is concluded that the reductions by carbachol and (-)-N6-phenylisopropyladenosine of isoproterenol-stimulated PLB phosphorylation and Tnl phosphorylation are pertussis toxin-sensitive.

Animals↗
PubMed1994

[Surgical treatment of large goiters extending into the retrosternal space].

The authors describe the characteristics of primary and secondary goitres reaching as far as the retrosternal space. 154 operations of retrosternal goitres during a five-year period account for 16.7% of all operations of the thyroid gland. The great majority (97.4%) of operations was made from a cervical approach. The authors express also their opinion on sternotomies in these operations; the reasons comprise also extensive goitres which cannot be removed across the upper thoracic aperture where the orientation on the position of major blood vessels is poor, when local invasion of the tumour into the neighbouring tissues is suspected, in some reoperations or when it is necessary to explore the mediastinum to differentiate other lesions. The very rare thoracotomic approach is reserved for large retrosternal goitres located in the posterior mediastinum.

Female↗
PubMed1994

[Elective total hip prosthesis management in patients over 80 years of age].

Ninety-five primary elective total hip prosthesis procedures were carried out in patients over 80 years of age (average 82.9 years). The results were studied retrospectively to determine the individual risk-advantage relationship and the general cost-advantage relationship taking the social aspects into consideration. Fractures and emergency procedures were excluded. Ninety-three percent of the patients had preexisting general illnesses. There were no local or general complications in the peri- and postoperative courses of 86% and 85%, respectively. The general complications included urological (6%), cardiovascular (5%) and abdominal (3%) problems. The only death (myocardial infarction) took place 4 weeks after the operation during the rehabilitation phase. The average hospital stay was 23.3 days; 20% of the patients were then able to return home, while 80% were sent to another institution for further care (geriatric department, rehabilitation), where the average stay was 36.7 days. The total inpatient treatment period was on average 52.3 days. At the time of the last follow-up, an average of 4.6 years postoperatively, 75% of the patients were alive with an average age of 87.4 years. Seventy-nine percent were still able to live alone and look after themselves; 81% were independent or only partially dependent (living in a retirement home). Ninety-three percent had no pain or only mild pain. If indicated, the operation risk factor for total hip prostheses in patients over 80 years is obviously low, and the results are good. This operation permits the patient to have many years free of pain, to remain independent, and to achieve a clearly higher quality of life. In this way one can also save on the high cost of many years of nursing care.

Activities of Daily Living↗
PubMed1993

In vivo analysis of the murine beta-myosin heavy chain gene promoter.

The 5' upstream region of the murine beta-myosin heavy chain (MHC) gene has been isolated and tested for its ability to drive gene expression in transgenic mice. Three classes of transgenic mice were generated. The constructs contained approximately 5000, 2500, and 600 base pairs of beta-MHC upstream sequence fused to the chloramphenicol acetyltransferase gene and were termed beta 5, beta 2.5, and beta .6, respectively. Muscle-specific expression was observed with all three constructs. However, only the beta 5 lines directed high levels of muscle-specific transgene expression in both pre- and postbirth mice. Expression driven by the two shorter constructs was two to three orders of magnitude lower when the chloramphenicol acetyltransferase specific activities were compared. These data suggest that a distal-positive element directs high levels of gene expression in the ventricle and in slow skeletal muscles. Analyses of transgene expression during heart maturation revealed that some of the beta 5 lines were not able to respond in an appropriate manner to developmental transcriptional cues. Unlike the endogenous beta-MHC gene, which is down regulated in the ventricles around the time of birth, reporter gene expression in the majority of the lines generated was not shut off in the ventricles of the adult animals. These data indicate that high levels of muscle-specific beta-MHC gene expression are dependent upon the combinatorial interactions of a number of sequence elements that are distributed over a large region of the gene's upstream sequence.

Aging↗
PubMed1993

Transgenic analysis of the thyroid-responsive elements in the alpha-cardiac myosin heavy chain gene promoter.

The role of two putative, cis-acting thyroid hormone-responsive elements, TRE1 and TRE2, located at -129 to -149 and -102 to -120, respectively, on the murine alpha-myosin heavy chain (MHC) gene, has been investigated in transgenic mice. These motifs are present in a 4.5-kilobase fragment lying upstream of the transcriptional start site of the mouse alpha-MHC gene: this fragment directs appropriate expression of a reporter gene in transgenic mice (Subramaniam, A., Jones, W. K., Gulick, J., Wert, S., Neumann, J., and Robbins, J. (1991) J. Biol. Chem. 266, 24613-24620). Here, we independently mutate the TRE1 and TRE2 elements by base substitution. The mice were analyzed for transgene expression in different muscle and non-muscle tissues including the atria and ventricles. Normal levels of transgene expression were observed in euthyroid mice carrying a mutation in TRE1. In contrast to these results, mice in which TRE2 was mutated showed reduced levels of CAT activity in both the atria and ventricles, suggesting a previously undefined role for this element in the constitutive up-regulation of the alpha-MHC gene. In hypothyroid mice carrying either of these mutations, the complete cessation of ventricular expression of the chloramphenicol acetyltransferase transcripts that takes place in the alpha-5.5 (wild type) animals did not occur.

Animals↗
PubMed1993

Pertussis toxin unmasks stimulatory myocardial A2-adenosine receptors on ventricular cardiomyocytes.

Pertussis toxin-pretreatment abolished the contractility- and cAMP-decreasing effects of the A1-adenosine receptor agonist (-)-N6-phenylisopropyladenosine (R-PIA) in the presence of isoprenaline in isolated ventricular cardiomyocytes from guinea-pigs, indicating that these stimulatory effects of A1-adenosine receptors are mediated via pertussis toxin-sensitive G-proteins. Furthermore, the decrease in contractile response by the A1/A2-adenosine receptor agonist 5'-N-ethylcarboxamidadenosine (NECA) was abolished. Moreover, NECA increased cAMP content in pertussis toxin-pretreated cells. Thus, pertussis toxin unmasked cAMP-augmenting effects of NECA, indicating that NECA can stimulate A2-adenosine receptors on cardiomyocytes. Thereby, the present study provides evidence that besides cAMP- and contractility-decreasing A1-adenosine receptors, cAMP-increasing A2-adenosine receptors coexist on ventricular cardiomyocytes, which do not influence contractile response.

Adenosine↗
PubMed1993

Mechanisms of beta-adrenergic stimulation of cardiac Ca2+ channels revealed by discrete-time Markov analysis of slow gating.

Individual cardiac Ca2+ channels cycle slowly between a mode of gating in which the channel is available to open, and one in which the channel remains silent. The regulation of this multisecond cycling process by isoproterenol was investigated by single-channel recording and the development of a discrete-time Markov model that describes the slow switching among modes in terms of (de) phosphorylation reactions. The results provide evidence that isoproterenol increases Ca2+ channel activity by a reciprocal regulatory mechanism: not only is the phosphorylation rate of the channel increased, but also the dephosphorylation rate decreased. The discrete-time Markov formalism should prove useful as a general tool for understanding the mode switching demonstrated by a number of ionic channels.

1-Methyl-3-isobutylxanthine↗
PubMed1993

Evidence for physiological functions of protein phosphatases in the heart: evaluation with okadaic acid.

Okadaic acid exerts a positive inotropic effect in cardiac preparations. We studied whether the positive inotropic effect of okadaic acid in cardiac preparations could be due to phosphatase inhibition and whether this inhibition affects the phosphorylation of cardiac proteins. In papillary muscles from guinea pigs, 30 microM okadaic acid increased force of contraction to 175% of predrug value. In isolated guinea pig ventricular cardiomyocytes, okadaic acid augmented single Ca(2+)-channel currents by enhancing channel availability. In homogenates from ventricles, 1 microM okadaic acid completely inhibited phosphorylase a phosphatase activity. In isolated 32P-labeled ventricular cardiomyocytes, 30 microM okadaic acid increased phosphorylation of phospholamban (PLB) and troponin inhibitor (TnI) to 325 and 284% of control, respectively. Furthermore, 30 microM okadaic acid increased phosphorylation of a hitherto unknown 23-kDa protein to 352% of control. It is concluded that the effects of okadaic acid could be mediated by increasing the phosphorylation state of several proteins including PLB, a 23-kDa protein, and TnI.

Animals↗
PubMed1993

A1-adenosine receptor-mediated inhibition of isoproterenol-stimulated protein phosphorylation in ventricular myocytes. Evidence against a cAMP-dependent effect.

cAMP content and protein phosphorylation were determined in unlabeled and 32P-labeled guinea pig ventricular myocytes. Isoproterenol (10 nM, 37 degrees C, 10 seconds) increased cAMP content (236%) and phospholamban (265%) and troponin I (135%) phosphorylation in ventricular myocytes. When isoproterenol (0-300 nM) and the A1-adenosine receptor agonist (-)-N6-phenylisopropyladenosine (PIA, 1 microM) or the A1- and A2-adenosine receptor agonist 5'-(N-ethylcarboxamido)-adenosine (NECA, 1 microM) were administered simultaneously, both adenosine receptor agonists attenuated phospholamban phosphorylation to approximately the same extent (40%). The EC50 value for isoproterenol to phosphorylate phospholamban was 8 +/- 1 nM (n = 3), which increased to 31 +/- 4 nM (n = 3) in the presence of PIA or NECA. IC50 values for PIA or NECA to decrease the phosphorylation of phospholamban were 30 or 32 nM in 10 nM isoproterenol-stimulated cells and 80 or 85 nM in 30 nM isoproterenol-stimulated cells. Both adenosine receptor agonists failed to inhibit the phosphorylation of troponin I. However, acetylcholine (2 microM) in the presence of 10 nM isoproterenol inhibited phosphorylation of phospholamban as well as troponin I in ventricular cells. These effects were antagonized by 10 microM atropine. The effects of PIA and NECA on phosphorylation were antagonized by the A1-selective adenosine receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (1 microM) but not by the A2-selective adenosine receptor antagonist 9-chloro-2-(2-furanyl)-5,6-dihydro-1,2,4,triazolo(1,5-c)quinazolin -5-imine (1 microM). PIA and NECA did not reduce cAMP levels in isoproterenol-stimulated cells. We conclude that phospholamban phosphorylation was inhibited by A1-adenosine receptor activation and that these effects on phospholamban phosphorylation cannot be explained by a reduction in cAMP levels.

Acetylcholine↗
PubMed1993

[A multidisciplinary approach in the treatment of endocrine orbitopathy].

Despite the knowledge of immunological mechanisms of Graves-Basedow's disease the pathogenesis of endocrine orbitopathy remains obscure. Apart from the most frequent association with GB disease it may occur also in patients with primary hypothyroidism, Hashimoto's thyroiditis or in rare instances in euthyroid patients not suffering from thyroid disease. Endocrine orbitopathy is a typical example of a disease with a multidisciplinary approach to its diagnosis and treatment. In the submitted paper the authors demonstrate the collaboration of four clinics of the Faculty Hospital when dealing with this problem. Complete or almost complete removal of the thyroid gland leads within 1-4 years to regression of the protrusion of the bulbus by 1 mm. In combination with decompression of the orbit by a modification of Ogura's and Walsh's method improvement of visual acuity by 50% was achieved and the mean value of the exophthalmus diminished by 3.5 mm.

Exophthalmos↗