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Biomedical subjects

H Neef

Publications and source records attributed to H Neef.

At least 37 records · Page 2Linked to original sources
PubMed1995

[Preoperative status of serum proteins in lung surgery patients].

The preoperative serum-protein-status of 91 patients was investigated with a laboratory-screening in order to find out the patients with a malnutrition and consequently with a high risk of postoperative complications. The diagnosis was the basis for the classification in groups. There were no significant differences between values of our patients and normal values of a control group in protein, albumin, prealbumin, transferrin, cholinesterase, alpha-1-antitrypsin and haemopexin. Nutrition parameters are of limited value of preoperative risk-screening in operable lung cancer patients.

Adenocarcinoma↗
PubMed1994

Specificity of coenzyme binding in thiamin diphosphate-dependent enzymes. Crystal structures of yeast transketolase in complex with analogs of thiamin diphosphate.

The three-dimensional structures of complexes of yeast apotransketolase with the coenzyme analogs 6'-methyl, N1'-pyridyl, and N3'-pyridyl thiamin diphosphate, respectively, were determined with protein crystallographic methods. All three coenzyme analogs bind to the enzyme in a fashion highly similar to the cofactor thiamin diphosphate. Thus, either one of the hydrogen bonds of the pyrimidine ring nitrogens to the protein is sufficient for proper binding and positioning of the cofactor. The lack of catalytic activity of the N3'-pyridyl analog is not due to incorrect orientation of the pyrimidine ring, but results from the absence of the hydrogen bond between the N1' nitrogen atom and the conserved residue Glu418. The structure analysis provides further evidence for the importance of this conserved interaction for enzymatic thiamin catalysis.

Coenzymes↗
PubMed1994

The adenosquamous lung carcinoma: clinical and pathological characteristics.

The adenosquamous carcinoma is a rare combined tumour of non-small cell lung cancer (NSCLC). The survival prognosis of surgically treated patients with adenosquamous carcinoma and patients with squamous cell carcinoma, large cell carcinoma or adenocarcinoma were compared during a study. Two hundred and seventyfive patients who had been treated surgically because of primary lung cancer in the Department of Thoracic-Surgery at the Martin-Luther-University Halle-Wittenberg between 1980 and 1989 were evaluated. The five year survival study of 172 patients who underwent resection because of squamous cell carcinoma was 45%, the one of patients with adenocarcinoma (n = 84) was 27%. 26% was the five year survival rate of the patients (n = 9) with large cell carcinoma. Of 13 patients (4%) with adenosquamous carcinoma none survived five years after surgical treatment. The two year survival rate was 28%. The presented results demonstrate the poor survival prognosis of patients suffering from adenosquamous carcinoma and ask for an adjuvant therapy.

Adenocarcinoma↗
PubMed1993

Effects of metal ions, thiamine diphosphate analogues and subunit interactions on the reconstitution behaviour of pyruvate decarboxylase from brewer's yeast.

The reconstitution of pyruvate decarboxylase starts with reversible binding of thiamine diphosphate and Mg2(+)-ions to the apoenzyme, followed by a rate-limiting conformational change to the catalytically active holoenzyme. Investigations with diphospho-esters of 4-methyl-5-(2-hydroxyethyl)thiazolium derivatives have shown that the diphosphate residue of thiamine diphosphate is the most important part of the coenzyme responsible for the first reversible binding step. Methylation of the N1'-atom of the pyrimidine ring of thiamine diphosphate or 4'-oxythiamine diphosphate prevents the coenzyme from binding stably to the apoenzyme, so that the methylated coenzyme displays no coenzyme activity. In contrast, thiamine diphosphate analogues with bulky residues on the neighbouring C2'-atom of the pyrimidine ring form active holoenzyme complexes. This result shows the essential role of the N1'-atom of thiamine diphosphate in stable cofactor binding. The cofactor binding rate to the dimeric and tetrameric apoenzymes indicates that the cofactor is located in the contact regions of the subunits in the tetrameric enzyme.

Binding Sites↗
PubMed1990

The role of surgery in diagnosis and treatment of mediastinal malignancies.

Primary mediastinal malignancies should be treated aggressively using a multidisciplinary approach since some are curable. Surgery is indicated in almost all cases of mediastinal masses with the exception of malignant lymphomas. The question of operability must be placed at the beginning of diagnostic measures in a mediastinal mass. Exact decisions about local operability are often only possible after thoracotomy. Long lasting diagnostic maneuvers are therefore to be avoided. Histological assessment of masses in the middle or anterior mediastinum is possible by mediastinoscopy or other methods. Thus in malignant lymphomas or metastases thoracotomy can be avoided. In the other mediastinal spaces exact histology remains unknown until thoracotomy. If exploration shows inoperability, mass reduction is performed to decrease the space-taking process and to provide better chances for radiotherapy and chemotherapy. Primary radiotherapy and/or chemotherapy are indicated in malignant lymphomas and germ cell tumors. After these measures the indication for surgical excision in tumors has to be proved. X-ray screening techniques need to be improved to aid in early detection, higher extirpation rates, and thus better chances for cure. Because the amount of cases in individual departments is low multicenter collaboration will be required to define the optimal combined modality approach.

Adolescent↗
PubMed1990

[Risk assessment of bronchial cancer surgery using quantitative lung perfusion scintigraphy].

28 patients with bronchogenic carcinoma were studied to predict lung function after thoracic resectional surgery, i.e. the functional operability, employing preoperative vital capacity (VC), forced expiratory volume (FEV1) and perfusion lung imaging. The perfusion scan was divided into 12 regions of interest which were semiquantitated to determine the relative distribution of perfusion as a fraction of the total perfusion. The planned reduction of lung parenchyma was expressed as percent of total perfusion, and the expected decrease in VC and FEV1, i.e. the predicted postoperative function of the lung, was calculated. The comparison of the predicted functional lung capacity with the re-estimated lung function (VC and FEF1) 6 months after surgery showed high correlation coefficients for both VC and FEV1. Semiquantitative perfusion scintigraphy of the lung helps to determine the extent of surgery possible in the individual therapy of lung cancer and is especially important in patients with a high operative risk.

Carcinoma, Bronchogenic↗
PubMed1990

[Model and experimental animal studies of the use of hand-controlled catheter-jet-ventilation (CJV) by plastic replacement of the tracheobronchial tree].

Pressure and volume flow measurements were performed on a simple model of the tracheobronchial tree using a catheter-jet-ventilation apparatus. This type of respiration is particularly favourable in tracheo-bronchial surgery, i.e. resections and anastomosing, due to the experience of model as well as animal experiments. Under consideration of the particularities of catheter-jet-ventilation, this type of respiration provides excellent conditions for the surgeon. This is valid for the overview of the site of operation and possible manipulation within this region. This method of respiration is suggested as a reliable tool in the hands of less skilled anaesthetists, too, for its easy handling.

Anastomosis, Surgical↗
PubMed1990

[Evaluation of reflux behavior of esophago-jejunal anastomoses following gastrectomy].

Functional results of 48 gastrectomies are reported. The applied techniques of the construction (jejunoplicatio) are judged for the safety of the anastomosis. 29 patients (60.5%) were examined for the degree of jejunooesophageal reflux after a survival time of 1 year. Antireflux techniques of anastomosis had good functional results measured by manometry and pH-metry.

Anastomosis, Roux-en-Y↗
PubMed1989

[Late results of resection treatment of bronchiectases with special reference to functional studies].

In 83 patients an unilateral pulmonary resection because of bronchiectasis was performed. The indication was unsuccessful medical treatment. Forty seven patients were re-examined clinically and radiologically and with spirometry and ergooxytensiometry 13.2 years (average) after operation. Good functional results were found in 72.1% of the patients. This justifies pulmonary resection for bronchiectasis even in the era of potent antibiotics. We preferred lobectomy because of its low postoperative complication rate and good functional late results. In bilateral bronchiectasis we operated upon the side with the advanced disease.

Adolescent↗
PubMed1985

The effect of thiamine pyrophosphate modification on its coenzyme function in a transketolase-catalyzed reaction.

The coenzyme function of TPP analogues: 4'-NH-methyl-TPP,6'-methyl-TPP and 6'-methyl-4-nor-TPP has been studied in a transketolase-catalyzed reaction. Their dissociation constants have been found with the aid of the circular dichroism method, and coenzyme activity has been determined in a complete transketolase reaction, involving the substrate-donor and the substrate-acceptor, and also at the intermediate stage (by the alpha-carbanionic intermediate oxidation rate). The coenzyme activity values have been found different and largely dependend on the nature of the substrates used. A possibility of TPP functioning by the "two-center mechanism" in a transketolase-catalyzed reaction is discussed.

Kinetics↗