Search PubMed⌕ Search

Biomedical subjects

W Hofmann

Publications and source records attributed to W Hofmann.

At least 199 records · Page 11Linked to original sources
PubMed1989

[Dosage adjustment of drugs during continuous hemofiltration. Results and practical consequences of a prospective clinical study].

In 43 ICU patients undergoing continuous volume constant hemofiltration (CVHF), the pharmacokinetics of 12 drugs were investigated to ensure correct dosage adjustments. Under conditions of CVHF, maximum doses were defined for cefotaxime, ceftazidime, digoxin, digitoxin, imipenem, metronidazole++, netilmicin, phenobarbital, phenytoin, theophylline, tobramycin, and vancomycin. For the estimation of sufficient doses without blood level measurements, sieving coefficients (S) were calculated by a new method. In addition, S was integrated as a CVHF-specific factor into a common equation for drug dose adjustment in patients with renal insufficiency. The regression of dosage received from kinetics on blood-level-independent equation adjustment was r = 0.9923. Since the volumes of distribution in ICU patients are variable, it is suggested that further drug monitoring is necessary for toxic drugs.

Adult↗
PubMed1988

Cryo-electron microscopy of insect flight muscle thick filaments. An approach to dynamic electron microscope studies.

Suspensions of isolated insect flight muscle thick filaments were embedded in layers of vitreous ice and visualized in the electron microscope under liquid nitrogen conditions. The unfixed, unstained, unsupported and fully hydrated filaments were observed under various biochemical conditions. We demonstrate here the first successful application of this method to thick filaments, and show that this is a possible approach to following dynamic processes by rapid freezing and electron microscopy.

Animals↗
PubMed1988

High-performance concanavalin A affinity chromatography of liver and hepatoma membrane proteins.

Although the separation of water-soluble glycoproteins by high-performance (HP) concanavalin A (ConA) affinity chromatography (AC) is feasible, irregularities may be encountered with hydrophobic glycoproteins. The separation of plasma membrane glycoproteins from liver and Morris hepatoma 7777, used as a model, showed that not only the interaction between the lectin and the oligosaccharide portion of the glycoproteins plays a role in the chromatographic process, but also the hydrophobic interactions between sample and lectin and between sample and support. In this, the characteristics of the support, such as surface hydrophobicity and pore size, play an important part. It was found that a portion of the ConA is not covalently bound to the column, especially when elution is carried out with buffers containing detergents. Moreover, some extremely hydrophobic proteins could only be eluted from the column when high concentrations of detergents [1% (w/v) or higher] were applied. Despite these difficulties, four membrane glycoproteins from the liver with apparent molecular weights of 60, 80, 100 and 110-120 kilodaltons could be highly enriched by ConA HPAC. These proteins were further fractionated according to their strength of binding to the ConA and their different hydrophobic characteristics, using various detergents as eluents.

Animals↗
PubMed1988

The B cell-associated CD37 antigen (gp40-52). Structure and subcellular expression of an extensively glycosylated glycoprotein.

The human B lymphocyte-associated CD37 antigen (gp40-52) has been characterized by the monoclonal antibody HD28. The CD37 antigen is strongly expressed on surface immunoglobulin positive B lymphocytes and weakly on a subpopulation of T lymphocytes and myeloid cells. The total molecular mass of the antigen ranges from approximately 40 to 52 kDa in B cell-derived leukemias and malignant lymphomas as well as in normal and anti-mu/B cell growth factor-activated tonsillar B cells. The polydisperse nature of the electrophoretic pattern of the CD37 antigen was found to be due to a microheterogeneity in its carbohydrate moiety. Biochemical analysis showed that the CD37 antigen derived from B cell-lines BJAB and LICR-LON-HMy2 consists of a single chain protein core of approximately 25 kDa to which two N-linked, complex carbohydrate antennae of various length are bound. The glycosylation of the molecule comprises about 50% of the total molecular mass. The molecule does not contain O-linked carbohydrate chains. In contrast, the non-Hodgkin's lymphoma cell line, OCI.LY1, which is growth-dependent on human serum, carries a CD37 antigen with an additional carbohydrate chain resulting in a total molecular mass of approximately 40 to 64 kDa. At the electron microscopy level, this cell surface-expressed antigen was found to be associated with intracellular vesicles. The subcellular distribution of the CD37 antigen may reflect a function of this antigen both at the cell surface and in the cytoplasm. We found that, both due to its peculiar biochemical structure and its ultrastructural distribution, the CD37 antigen closely resembles the 46-kDa species of the mannose 6-phosphate receptor. The implications of this possible congruence for the function of the CD37 antigen are discussed.

Animals↗
PubMed1988

Stochastic morphological model of the rat lung.

The laboratory rat is often used as a human surrogate in aerosol inhalation studies. Here we present a new stochastic model for the rat lung analogous to that for the human lung. Morphometric data on the tracheobronchial geometry of the rat lung provided by the Lovelace Inhalation Toxicology Research Institute were analyzed. The results of this statistical analysis reveal significant differences in diameters and branching angles between major and minor daughter tubes starting from the same bifurcation. As a consequence of the more monopodial airway branching in the rat lung compared to the more dichotomous structure of the human lung, we recommend classifying the rat lung airways by their diameters and not by generation numbers. The distributions of the geometric airway parameters and the correlations among them will be used for Monte Carlo deposition calculations.

Animals↗
PubMed1988

Quantitation of photochemically induced focal cerebral ischemia in the rat.

This study was carried out with a recently developed model of focal cerebral ischemia in the rat based on the photochemical induction of thrombotic stroke using the dye Rose Bengal. We examined the change in the volume of the lesion and brain water content, in separate groups of rats, at different times (1, 4, 24, 72, and 168 h) after the induction of the ischemic lesion. The volume of ischemic damage increased rapidly between 1 and 24 h after the ischemic insult and decreased between 24 and 168 h. The lesion at 168 h was significantly larger than that following 1 h of ischemia and similar to that obtained at 4 h, suggesting that the maximum extent of tissue damage (without the involvement of significant edema) was reached within the first 4 h in this model. The enlargement of the lesion after 4 h correlated closely with changes in brain water content.

Animals↗
PubMed1988

Isolation of immunoglobulins and their use in immunoaffinity HPLC.

For the isolation of monoclonal and polyclonal antibodies different high performance liquid chromatography (HPLC) and high performance affinity chromatography (HPAC) methods were investigated. Specially designed "mixed-bed" ion-exchange and hydroxylapatite columns as well as hydrophobic interaction columns were efficiently applied to the isolation of monoclonal antibodies. When these methods are used for the isolation of polyclonal antibodies from antiserum, the sample has to be pre-treated, e.g. by removal of serum albumin. Protein A HPAC is an easy method and quick to handle, especially for the preparative isolation of antibodies. The antibodies that do not bind to protein A, can be purified by protein G HPAC. If this method cannot be used because of the rather extreme elution conditions, hydroxylapatite, ion-exchange or hydrophobic interaction HPLC have to be considered as alternatives. We further concentrate on immunoaffinity HPLC with immobilized antibodies. This method has proved to be very effective for one-step isolation of antigens, even from very complex samples such as plasma membrane extracts. The problem with immunoaffinity HPLC is the quick deterioration of the columns, caused by increasing denaturing of the immobilized antibodies during elution. In order to solve this problem, an indirect method is recommended for analytical immunoaffinity HPLC. For this purpose, the antibodies are bound to a protein A HPAC column. The solution containing the antigens is then applied. After washing, the antigen-antibody complex is eluted from the column.

Animals↗
PubMed1988

[Accumulated occurrence of lipomatosis in a cattle herd in Assiut (Egypt)].

A total number of 30 native breed cows were used in this investigation. Ten animals were clinically healthy and kept as control, while 20 diseased cows were selected according to rectal findings. At the beginning of the disease, the cows appeared obese with marked deposition of fat in the subcutaneous tissue at the lumbosacral area, later on they became emaciated. Additional signs were digestive disturbance in form of diarrhea or constipation and tympany. Rectal examination revealed hard irregular masses of various size which were palpated in the pelvis, the perirenal area around the colon and the rectum. More information about the nature and character of the lesions were taken from slaughtered cows. Biochemical analysis, including total lipids, cholesterol triglycerides and creatine kinase, were carried out in both healthy and diseased cows. In advanced cases of bovine lipomatosis hyperlipemia and hypercholesterolemia as well as increased creatine kinase values were constant findings. The aetiology of this disease is still unknown.

Animals↗
PubMed1987

Carcinoid tumors of the thymus. An immunohistochemical study.

Five carcinoid tumors of the thymus were screened immunohistochemically for the occurrence of neuropeptides (ACTH, calcitonin, calcitonin gene-related peptide, cholecystokinin, gastrin, neurotensin, somatostatin, substance P), as well as of serotonin, chromogranin A, and neuron-specific enolase. Most of the patients exhibited local symptoms evoked by growing tumor masses in the upper mediastinum without any clinical evidence of endocrine activity. Light and electron microscopic examination showed characteristic uniform large epithelial cells in polar or palisade arrangement, containing variable amounts of electron-dense secretory granules. Only a few of the tested neuropeptide antisera reacted with the investigated tumors. Cholecystokinin-immunoreactive cell populations were seen in all tumors. Expression of neurotensin could be observed in three neoplasms, two of which also exhibited ACTH immunoreactivity. Chromogranin A-immunoreactive cells were found in two neoplasms. Neuron-specific enolase showed strong staining in three tumors, one of the tumors also being immunoreactive for calcitonin. The results were confirmed by control reactions. Apart from the demonstration that conventional marker proteins are not reliable in identifying all carcinoid tumors, the present study proves that the visualization of neuropeptide-immunoreactive cells in thymus carcinoids does not necessarily correspond to the manifestation of the clinical symptoms. Furthermore, each of the investigated neoplasms, as also known from other carcinoid tumors, appears to be able to produce more than one hormone.

Carcinoid Tumor↗
PubMed1987

[Detection of nephrotoxicity of human alpha 2b interferon with special reference to the analysis of urine enzymes in patients with chronic myeloid leukemia].

The nephrotoxic potential of alpha-interferon (IFN alpha-2b) was analysed in 21 patients with chronic myeloid leukemia. As particularly sensitive parameters in the detection of subclinical renal injury we measured the excretion of the following urinary enzymes: lactate dehydrogenase (LDH), gamma-glutamyltransferase (GGT), leucine arylaminidase (LAP), beta-galactosidase (GAL) and N-acetyl-beta-glucosaminidase (NAG). Additionally, protein excretion and urinary sediment were analysed. In 18 of 21 patients a significant increase in the excretion of LDH, LAP, GGT and NAG was found, in 6 patients there was an additional rise in the output of GAL. Eleven patients developed proteinuria up to 2 g/l, one patient excreted up to 9 g/l. Enzymuria and protein excretion decreased in all patients after reduction of the IFN alpha-2b dosage and disappeared in two patients following cessation of therapy. The high incidence of nephrotoxic events in patients with CML during IFN alpha-2b therapy might be mostly due to immunological or substance-specific effects.

Adolescent↗
PubMed1987

High-performance liquid affinity chromatography of liver plasma membrane proteins.

Plasma membrane proteins from liver were analysed by concanavalin A affinity and immunoaffinity high-performance liquid chromatography. In the method, four peptide bands with apparent molecular weights of 140,000, 120,000, 80,000 and 60,000 could be isolated. In the second method, with two immobilized monoclonal antibodies, two corresponding antigens--the membrane proteins dipeptidyl-peptidase IV and GP 110--could be highly purified from plasma membrane extract with good yield in only one step.

Animals↗