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Biomedical subjects

M Hofmann

Publications and source records attributed to M Hofmann.

At least 199 records · Page 11Linked to original sources
PubMed1990

Primary structure and functional expression of the alpha-, beta-, gamma-, delta- and epsilon-subunits of the acetylcholine receptor from rat muscle.

The isolation and characterization of five clones carrying sequences of the alpha-, beta-, gamma-, delta- and epsilon-subunit precursors of the rat muscle acetylcholine receptor (AChR) are described. The deduced amino acid sequences indicate that these polypeptides contain 457-519 amino acids and reveal the structural characteristics common to subunits of ligand-gated ion channels. The pattern of subunit-specific mRNA levels in rat muscle shows characteristic changes during development and following denervation, suggesting that innervation of muscle reduces the expression of the alpha-, beta- and delta-subunit mRNAs, suppresses the expression of the gamma-subunit mRNA, and induces expression of epsilon-subunit mRNA. Subunit-specific cRNAs generated in vitro were injected into Xenopus laevis oocytes, resulting in the assembly of two functionally different AChR channel subtypes. The AChR gamma, composed of the alpha-, beta-, gamma- and delta-subunits, has functional properties similar to those of the native AChRs in fetal muscle. The AChR epsilon, composed of alpha-, beta-, delta- and epsilon-subunits, corresponds to the end-plate channel of the adult muscle. Thus in rat skeletal muscle the motor nerve regulates the expression of two functionally different AChR subtypes with different molecular composition by the differential expression of subunit-specific mRNAs.

Amino Acid Sequence↗
PubMed1990

[Isocyanate-induced respiratory tract diseases in Switzerland].

From 1980 to 1986 the Swiss National Accident Insurance Company (SUVA) recognized isocyanate-induced airway diseases as an occupational illness in 245 cases, which are presented retrospectively. Since isocyanates are widely used they are found at a large variety of workplaces. At present, isocyanates are the most frequent cause of occupational asthma in the Swiss industrial field. After complete avoidance of any further exposure respiratory symptoms persisted or airway obstruction could still be documented in one third of patients. An unfavourable prognosis is significantly associated with the following factors: (1) bronchial obstruction (FEVl/VC) at first pulmonary function test; (2) RAST positive for isocyanates; (3) long latency period between onset of symptoms and end of exposure. Therefore, individuals with isocyanate-induced airway diseases must be immediately removed from any further exposure to these substances.

Adolescent↗
PubMed1990

[Treatment of coronary heart disease in the aged. When balloon dilatation, when surgery?].

Data from 3029 consecutive patients (2474 men, 555 women, mean age 59 [20-88] years) in whom coronary heart disease had been diagnosed by coronary angiography were studied with the object of identifying those patients in the older age group who are suitable for treatment by balloon angioplasty. There were 884 patients with a mean age of 70 (65-88) years, and 2145 patients with a mean age of 54 (20-64) years. Single vessel disease was less common in older patients (30% vs 44%; P less than 0.001), double vessel disease was equally common in both groups (28% vs 30%) and triple vessel disease was commoner in the elderly group (42% vs 26%; P less than 0.001). For elderly patients with single vessel disease conservative treatment was chosen in 50%, angioplasty in 49% and operative treatment in only 1%. Of elderly patients with involvement of two arteries, 44% were treated conservatively, 40% by angioplasty and 16% surgically. Of elderly patients with triple artery disease, 23% were treated conservatively, 8% by angioplasty and 69% operatively. This pattern was similar to that among younger patients. The success rate and the incidence of complications after percutaneous transluminal coronary angioplasty were similar in both age groups. In elderly patients with disease of only one or two coronary arteries the prospects of success and the risks are comparable to those in younger patients, but patients with triple artery disease often need bypass surgery.

Adult↗
PubMed1990

Ultrastructural localization of WGA, RCA I, LFA and SBA binding sites in the seven-day-old mouse embryo.

In the present investigation we localized binding sites for the lectins WGA (wheat germ agglutinin), RCA I (Ricinus communis agglutinin), LFA (Limax flavus agglutinin) and SBA (soya bean agglutinin) in the 7-day-old mouse embryo at the ultrastructural level. Lectin binding sites were localized on formaldehyde fixed embryos, embedded in LR-Gold, using gold-labelled lectins. Binding sites for WGA and RCA I were observed at the surface of the embryonic ectoderm oriented towards the proamnion cavity and the outer surface of the extraembryonic and the embryonic endoderm. Staining for SBA and LFA binding sites was seen in the basement membrane of the ectoderm. Moreover, binding sites for LFA were observed in the nucleoli of cells of the ectodermal, the mesodermal and the endodermal layer and in free ribosomes located in the cytoplasm of these cells.

Animals↗
PubMed1990

Reaction of mastication to occlusal changes induced by correction of mandibular prognathism.

Incisor-point masticatory movements of 22 patients were recorded before and after correction of mandibular prognathism. Chewing patterns and movement parameters were compared between preoperative and postoperative states and to corresponding quantities of 85 persons with normal dentitions. The prognathism patients most frequently revealed "chopping-type" patterns characterized by nearly vertical closing strokes, whereas mastication in the reference group was dominated by lateral grinding-type movements. There were no significant differences in the pattern distributions and parameter values between the preoperative and postoperative states. An individual assessment, considering random fluctuations of chewing behavior, showed that only five patients had changed their chewing mode possibly because of the treatment. Only a minor part of these changes could be directly related to the altered occlusion. It is concluded that the characteristic chewing mode of persons with mandibular prognathism does not interfere with the occlusal profile, and hence does not react to alterations.

Adult↗
PubMed1990

Enzyme-linked immunosorbent assay for the detection of porcine epidemic diarrhea coronavirus antibodies in swine sera.

An enzyme-linked immunosorbent assay (ELISA) for detecting serum antibodies to the porcine epidemic diarrhea coronavirus (PEDV) was established by using cell culture-grown PEDV as antigen for coating. Ultracentrifugation through 20 and 45% (w/w) sucrose cushions proved to be the best antigen purification method. Examination of 1024 swine sera showed a high specificity and a greater sensitivity of the ELISA, when compared with indirect immunofluorescence. Reference sera with high antibody titers to PEDV originated from two pigs experimentally infected with PEDV. Three different antigen purification methods and the advantages of the ELISA compared with an immunofluorescence test are discussed.

Animals↗
PubMed1990

Effect of head activator on proliferation, head-specific determination and differentiation of epithelial cells in hydra.

In hydra the differentiation of head-specific ectodermal epithelial cells from multipotent stem cells is a multistep process in which cell cycle progression is regulated at three restriction points. Head activator acts as a positive signal at these restriction points. At the G2/mitosis boundary of epithelial stem cells head activator functions as a mitogen, being necessary for cell division. Subsequently, in or before S phase, head activator acts as determinant to ensure commitment of epithelial cells to head-specific determination. This effect of head activator requires hundredfold-higher concentrations, and may also require longer incubation times, than for cell proliferation. Epithelial cells thus committed to head-specific differentiation become arrested in G2 as a third and last restriction point in the cell cycle. They require disinhibition by decapitation and probably the presence of head activator for final differentiation, which then occurs in G2.

Animals↗
PubMed1990

Histological and scanning electron microscopic alterations in ileal conduit depending on the time factor.

Five ileal conduit biopsies, taken after 1-7 years, were examined by light microscopy and scanning electron microscopy. The total height of the lamina mucosa decreased from 700 to 275 microns. The height of the villi diminished from 550 to 50 microns; the depth of the crypts increased from 130 to 244 microns and the villus-crypt index changed from 4.2 to 0.2. Signs of chronic inflammation could be observed. Scanning electron microscopy shows that the number of microvilli per cell was markedly reduced. There was a varied picture of different stages of atrophy. After 3 years microvilli could no longer be observed. In view of the prolonged urinary contamination time, it appears to be imperative to check neobladders with regard to possible carcinoma induction.

Cell Transformation, Neoplastic↗
PubMed1990

[New frontiers in the prosthodontic management of patients with loss of all or most of their teeth].

In view of the increasing life expectancy and the growing number of older people, the conservation of denture bearing tissue will become an essential task in the treatment of edentulous patients. According to a clinical survey it could be proved that about 60% of the female and 40% of the male complete denture wearers had a high degree of bone loss of the lower jaw. The standard factors of function are described, particularly emphasizing the importance of muscular denture stabilization, jaw relation and mode of occlusion. The conservation of remaining single-posted teeth is necessary, not only for psychical reasons, but also with regard to support and function of the dentures. The biomechanical principles of design and approved denture constructions are illustrated. In order to ensure long-term denture function and care for the bearing tissue, it is mandatory that excellent oral hygiene, proper denture care, and periodical recalls, at intervals of 1 year at most, be maintained.

Aged↗
PubMed1990

[Studies on canine guidance in complete dentures].

The effect of canine guidance with guiding angles of 70, 55 and 30 degrees in relation to the median sagittal plane and balanced occlusion on the kinetics of upper complete dentures was investigated both in an in-vitro-experiment and in patients. It appeared that canine-guided dentures led to considerable dislocations during tooth-guided lateral movements, whereas balanced occlusion caused only minor movements, which were always directed toward the alveolar ridge.

Cuspid↗
PubMed1990

[Electronic measurements of the masticatory muscles. 1: Methods of recording].

The application of surface electromyography as an aid in diagnosing craniomandibular dysfunction requires that pathological or treatment-induced changes of the EMG be distinguished with sufficient probability from random variations due to methodological or biological reasons. It was the aim of this study to determine the range of variability of elevator muscle EMG, to find experimental methods for improving reproducibility, and to establish evaluation procedures that allow the recognition of treatment-induced effects in the EMG even in the presence of great random variations. For this we measured the voltage/tension relation of the elevator muscles of 42 persons in the range of 20 to 500 N on up to 20 different days under constant experimental conditions. The majority of measurements revealed a non-linear correlation between EMG activity and resulting force, hence second order polynomials proved to be more appropriate than straight lines for representing the activity/tension correlation. Muscle activity was found to vary randomly from day to day within each individual. These fluctuations appeared as varying axis intersections, initial slopes and curvatures which are the determinants of the voltage/tension curves. In ten selected subjects random fluctuations were significantly higher when electrodes were repositioned by palpation of the muscle belly than with the aid of tattoos.

Bite Force↗
PubMed1990

[Electronic measurements of the masticatory muscles. 2: Interpretation of activity changes in the masticatory muscles].

In part II, a method is described which reduced the variations of the three determinants of the voltage/tension curves to the fluctuation of only one three dimensional variable. A way to estimate three dimensional regions for the fluctuations is shown. For a given level of significance, limits can be calculated that allow us to decide whether differences between post- and pre-treatment measurements are random or due to treatment.

Electromyography↗
PubMed1990

Amiodarone--efficacy and late potentials during long-term therapy.

This prospective study was intended to examine the influence of long-term amiodarone therapy on the parameters of the signal averaged ECG and their relation to simultaneously derived Holter monitoring data. For this purpose 27 patients with angiographically confirmed dilated cardiomyopathy or coronary heart disease and highgrade ventricular arrhythmias, in whom an average of four class I antiarrhythmic drugs had proven ineffective, were stabilized on amiodarone. Before the beginning of therapy, as well as after two months and subsequently every three months if possible, a resting ECG, a signal averaged ECG by the method of Simson and Holter monitoring were performed. Compared to the initial measurement we found a significant increase in the duration of the total filtered QRS complex, while the change in the voltage did not reach the significance level. The incidence of late potentials remained largely constant under amiodarone. In the long-term follow up Holter monitoring showed a relatively high responder rate of between 46 and 81% under amiodarone. No relation could be detected between the results of the signal averaged ECG and those of 24-h Holter monitoring.

Amiodarone↗
PubMed1989

Synthesis and secretion of plasminogen activators and plasminogen activator inhibitors in cell lines of different groups of human lung tumors.

Several human lung tumor cell lines derived from large cell, squamous cell, and small cell carcinomas, as well as from mesotheliomas of the lung have been investigated for their gene expression and secretion of urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA), and plasminogen activator inhibitors 1 and 2. All bronchogenic non-small cell carcinoma-derived cell lines studied could produce either plasminogen activators, their inhibitors, or both components, whereas in small cell lung carcinoma cell lines and cell lines derived from mesothelioma of the lung, no substantial amounts of any of these substances were synthesized. In detail, a large cell carcinoma-derived cell line, LCLC 97TM1, constitutively secreted large amounts of plasminogen activator. Northern blot analysis revealed RNA specific for u-PA and t-PA. Another large cell carcinoma-derived cell line, LCLC 103H, secreted smaller amounts of plasminogen activator and, additionally, plasminogen activator inhibitor. Specific mRNAs for u-PA and plasminogen activator inhibitors 1 and 2 were found in this cell line. In contrast, squamous cell carcinoma-derived cell lines secreted plasminogen activator only after treatment with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate; enhanced levels of u-PA, t-PA, and plasminogen activator inhibitor 1 mRNAs could then be demonstrated. The different expression of the plasminogen activator enzyme system distinguishes cell lines derived of non-small cell lung carcinoma from those of small cell lung carcinoma and may also reflect significant differences in the biological behavior of these tumor types.

Autoradiography↗
PubMed1989

Conformation of secretin in dimethyl sulfoxide solution. NMR studies and restrained molecular dynamics.

The solution conformation of the 27-residue polypeptide hormone secretin in dimethyl sulfoxide has been determined on the basis of 1H-NMR measurements. The experimental data set used in the structure determination consisted of 98 nuclear-Overhauser-enhancement-derived interproton and dihedral angle restraints from coupling constants. The NH-NH and H alpha-NH NOEs were determined from build-up rates, while the remaining distances were classified in a qualitative manner. The structure calculations consisted of two phases. First, dynamical simulated annealing calculations were carried out to find conformations of the peptide which satisfy NOE and phi dihedral restraints. The convergence of ten calculated structures was good except for those regions of the molecule where NOE data were not unambiguous. From the calculated set another initial structure was built which was again minimized in several 5-ps calculations now employing the full empirical energy function. The resulting structures of secretin reveal conformationally well-defined regions, but not a single uniform secondary structure. The structure is different from the calculated structure from trifluoroethanol/water measurements.

Dimethyl Sulfoxide↗
PubMed1989

Quantitation, biological and physicochemical properties of cell culture-adapted porcine epidemic diarrhea coronavirus (PEDV).

The porcine epidemic coronavirus (PEDV), tentatively classified as a coronavirus, was adapted to Vero cells and a plaque test developed for infectivity titration, allowing us to test the biological and biophysical properties of the virus. Growth kinetics showed peak titers of 10(5.5) plaque-forming units ml-1 15 h after infection. Filtration experiments and electron microscopy revealed a particle diameter between 100 and 200 nm. The buoyant density of the virus was 1.18. The particle lost its infectivity on treatment with lipid solvents. Virus replication could not be inhibited by 5-iodo-2'-deoxyuridine. PEDV was moderately stable at 50 degrees C, but heat sensitivity was not altered by divalent cations. At 4 degrees C, the virus was stable between pH 5.0 and 9.0, but at 37 degrees C stability was restricted to the pH range 6.5-7.5. Viral infectivity was not impaired by ultrasonication or by multiple freezing and thawing. PEDV was not neutralized by transmissible gastroenteritis virus antiserum. On the basis of the tests carried out, PEDV is a pleomorphic, enveloped RNA virus with a particle diameter of approximately 150 nm and a buoyant density of 1.18. Infectivity depends on the presence of trypsin, and infected cells show a tendency to fuse and to form syncytia. All of these properties, as well as its physicochemical characteristics, allow PEDV to be classified as a coronavirus.

Animals↗
PubMed1989

[Experimental infection of calves and sheep with bovine Giardia isolates].

9 Giardia-free calves were artificially infected with 1.5-5.1 x 10(6) Giardia cysts originating from Swiss cattle ("bovine isolates"). In 4 of these animals the course of infection was examined. After prepatent periods of 7-8 days all calves excreted high numbers of Giardia cysts for 60-112 days. During patency on 44% of the examination days Giardia cysts and antigen could be detected simultaneously in faecal samples using the flotation method and a sandwich-ELISA, respectively. With the exception of light diarrhoea lasting only for some days at the beginning of patency no other symptoms occurred. Further 5 artificially infected calves were submitted to autopsy. Giardia trophozoites were detected in 4 calves in the jejunum and in 1 animal in the ileum (peroxidase-antiperoxidase method). All animals were simultaneously infected with Campylobacter spp. and/or Rota- and Corona-virus. Electronmicroscopically mucosal attachment sites of Giardia trophozoites had intact microvilli and enterocytes. In various parts of the intestine blunting and flattening of the villi and cellular infiltrations of the mucosa were present. These alterations in calves are generally associated with bacterial and/or viral infections of calves. A Swiss bovine Giardia cyst-isolate was transmitted to 4 Giardia-free conventionally maintained lambs which excreted Giardia cysts after prepatent periods of 10-21 days for 31-61 days.

Animals↗