PubMed Health⌕ Search

Biomedical subjects

M Geiser

Publications and source records attributed to M Geiser.

At least 37 records · Page 2Linked to original sources
PubMed1996

Airway surfactant, a primary defense barrier: mechanical and immunological aspects.

Epidemiologic studies have shown strong associations between mortality and morbidity from respiratory and cardiac causes and exposure to fine (PM10), but not coarse, particulates. A plausible mechanistic explanation for these associations is lacking. It has been shown that particles may be retained for an extended period of time in the airways, and that their clearance is inversely proportional to particle size. Such particles are localized in close association with the airway epithelium, and if they consist of low surface energy material, will be coated with an osmiophilic layer, consistent with surfactant. Particles are displaced into this position by surface and line tension forces exerted by the surfactant film at the air-aqueous interface. Particle displacement due to line tension is much greater for smaller particles in the micrometer range. The surface forces acting on the particles leave deep indentations on the epithelial cells. During the displacement process they may come into contact with airway macrophages in the mucous layer and/or dendritic cells situated in the airway epithelium. The smallest particles may even penetrate the mucosa to enter the interstitial compartment. In addition to altering the physical properties of particles, surfactant coatings reduce particle toxicity and enhance phagocytosis by opsonization. We speculate that surfactant acts as a primary defense barrier and plays a role in antigen presentation and elimination at the air-mucus interface of the airways.

Air Pollutants↗
PubMed1995

Paradoxical effects of bleomycin and heavy water (D2O) in mice.

Bleomycin (BLM) lacks many side effects of other cytostatic drugs. Pulmonary toxicity is the major dose-limiting effect of BLM. This is based in part on generation of free radicals. It is conceivable that deuterium in body fluids lessens the production of free radicals, thus preventing or diminishing the morphologic expression of pulmonary BLM toxicity. We therefore studied the effect of moderate deuteration of body fluids on BLM-induced lung damage in BALB/c-mice. In addition to conventional histopathological methods, we used a vertical sectioning design for stereological estimation of pulmonary volumes and surface areas. BLM (low/medium/high dose: 25/50/75 IU/kg body weight) was injected i.p. once a week for 6 weeks. Half the mice drank deuterated water before, during and after BLM treatment. Three weeks after the last injection, the lungs were fixed by airway instillation. Deuterated animals treated with BLM lacked signs of irreversible BLM-induced pulmonary damage. Conversely, focal sub-pleural fibrosis and fibrosing alveolitis were present in BLM-treated mice drinking tap water. Deuterated mice had stereological values for almost all lung parameters that were lower than in non-deuterated mice. The organ-specific advantage of deuteration was offset by marked enhancement of systemic toxicity of BLM. We conclude that (1) moderate concentrations of deuterium may prevent the development of fibrosing alveolitis in BLM-treated mice, possibly by reducing proliferation of alveolar fibroblasts, and, less probably, by impairing generation or enhancing capture of free radicals; (2) the toxicity of BLM was enhanced by ingestion of deuterium, resulting in morphological liver alterations and increased mortality.

Animals↗
PubMed1995

Evaluation of antibodies fused to minor coat protein III and major coat protein VIII of bacteriophage M13.

A gene coding for an anti-(2-phenyl-5-oxazolone) single-chain Fv antibody (Ab) fragment (anti-phOx scFv) was cloned in-frame into phagemid vectors upstream from genes encoding (i) the wild-type (wt) minor coat protein (cp) III of the filamentous bacteriophage M13 of Escherichia coli, (ii) a truncated version of cpIII (amino acid (aa) positions 198-406), (iii) the wt major cpVIII, or (iv) a hybrid of interleukin-1 beta (IL-1 beta; aa 10-152) and wt cpVIII. Recombinant (re-) phage obtained by phagemid rescue were examined for the efficiency of displaying these various anti-phOx scFv::cp hybrids with commercially available anti-M13 enzyme-linked immunosorbent assays (ELISA), by immunoblotting with an anti-c-myc Ab, and by selection experiments. We found that the highest ELISA signals were obtained with the cpIII constructs and also that more immunoreactive material was detected by blotting than with Ab::cpVIII fusions. Consequently, more scFv::cpIII than scFv::cpVIII phage could be recovered in micropanning experiments with the antigen phOx as target.

Amino Acid Sequence↗
PubMed1995

Selection procedures for nonmatured phage antibodies: a quantitative comparison and optimization strategies.

Libraries of peptides and proteins can be displayed on the surface of filamentous bacteriophage. The efficient capturing of phage recognizing a defined target molecule remains a serious obstacle, in particular when the phage are present at a low frequency or have a reduced affinity like nonmatured phage antibodies and when the availability of target molecules is limited. We present theoretical considerations and experimental data which allowed us to substantially improve microselection under these conditions. We used a model phage displaying an anti-(2-phenyl-5-oxazolone) single-chain Fv antibody fragment. Following standard protocols and aiming at a low nonspecific binding, only 3.6 x 10(-3)% of the phage input could be recovered from a single round of selection performed in the wells of a microtiter plate. Our results explain why this often employed panning in wells is not efficient, especially with high-molecular-weight target molecules. We devised a procedure which increased the probability of microselection by a factor of 34. An alternative capturing method using immunotubes with a new protocol decreased the amount of required work by a factor of 30. In the case of a nonlimited supply of target molecules, column-affinity chromatography is recommended.

Antibodies, Viral↗
PubMed1995

Efficiency of airway macrophage recovery by bronchoalveolar lavage in hamsters: a stereological approach.

Macrophages play a central role in the defence of the respiratory tract against deposited particles. In addition to the well-studied alveolar macrophages, airway macrophages have been recognized as an important clearance factor. Bronchoalveolar lavage (BAL) has been used for functional and morphological investigations of macrophages in vitro, assuming that all macrophages are removed with equal probability from the lung surface. Airway macrophages have been found in close contact with the epithelial cells. These macrophages may not be easily removed by lavage, and they might constitute a functionally different macrophage population. We have tested the hypothesis that there exists a population of macrophages in the conducting airways that resists removal by lavage. We lavaged the lungs of four hamsters and fixed the lungs, thereafter, by intravascular perfusion. The number of macrophages in the intrapulmonary conducting airways was estimated with an unbiased stereological technique, the fractionator, and compared to the number of macrophages in the airways of four hamsters whose lungs had not been lavaged prior to fixation. This in situ study revealed that, in hamster lungs, 42% of the airway macrophages were not removed by BAL and that about 5% of all macrophages in the BAL fluid were airway macrophages. Additionally, ultrastructural alterations of the airway epithelium were found. It is concluded that there exists a population of airway macrophages that resists lavage. This is an aspect which has to be considered in studies performed with macrophages obtained by BAL, since they could represent a functionally different macrophage population.

Animals↗
PubMed1994

[Schizophrenia from the viewpoint of family members].

After a short history of the origin of Schizophrenia Fellowships throughout the world, the difficulties besetting an efficient management of the disease are mentioned. Some of them arise from the characteristic features of the disease and the still awaited understanding of the etiology. Further serious obstacles arose from the century-old discrimination against the mentally ill, simplistic theories on the etiology of the disease, misuse and discouragement of drug treatment, discrediting of psychiatric hospitals and the lack of legislation to provide the patient with the right to competent treatment and rehabilitation. The families of schizophrenic patients expect maximum help from humane caring for the patient, with absence of psychological theories, intensive research into the biological causes of the disease, and a change in legislation respecting the possibilities of modern treatment. Families are not in need of treatment but of proper information, practical advice, unflagging support and cooperation between patients, family members, therapists and psychiatric institutions. As a compensation for their contribution to caring for the patient they would appreciate a well functioning emergency service to manage critical situations and the abolition of unnecessary obstacles to competent treatment. Only successful investigation of the causes of the disease can bring a fundamental therapeutic improvement.

Counseling↗
PubMed1994

The effect of particle inhalation on macrophage number and phagocytic activity in the intrapulmonary conducting airways of hamsters.

The number and functions of macrophages in the lungs are crucial factors for prevention and development of lung disease caused by inhaled particles. To examine whether airway macrophages are attracted to the site of particle deposition and what proportion of these macrophages is involved in phagocytosis, aerosols of 6-microns polystyrene particles (PSP) were inhaled by Syrian Golden hamsters under controlled conditions through an inhalation tubule and their lungs were fixed by intravascular perfusion within 20 min (PSP-1, PSP-1a), 40 min (PSP-2), and 24 h (PSP-3) after the beginning of the inhalation. The number and the phagocytic activity of airway macrophages were studied in situ with a fractionator, a stereologic method, on light microscopic sections. No significant increase in macrophage number was detected for the groups PSP-1 and PSP-1a. The increase for group PSP-2 was, however, between 2- and 3-fold, whereas for group PSP-3 the increase was between 1.5- and 2.5-fold with respect to control animals, which had inhaled ambient air through an intubation tubule (C-2) and whose lungs had been fixed after 40 min. There were no significant differences among the four groups with respect to the proportion of airway macrophages that had phagocytized polystyrene microspheres. Twelve to fifteen percent of the macrophages were found to be involved in phagocytosis. In the case of the mean number of particles per phagocytizing macrophage, there was a significant decrease for the PSP-3 group with respect to the pool of the three groups PSP-1, PSP-1a, and PSP-2 taken together. These studies demonstrate (1) that airway macrophages are rapidly recruited to the sites of particle deposition and (2) that only a small proportion of very active macrophages contributes to the clearance of particles, suggesting a great potential of airway macrophages to interact with many more particles than the hamsters were exposed to in this study.

Administration, Inhalation↗
PubMed1993

Surfactant and inhaled particles in the conducting airways: structural, stereological, and biophysical aspects.

We have investigated the displacement into the sol phase of inhaled particles deposited in the intrapulmonary conducting airways. Hamsters inhaled an aerosol of monodisperse polystyrene particles of 6 microns diameter. Their lungs were fixed by intravascular perfusion, and light and electron microscopy was used to study the epithelial coating. The surfactant film at the wall-air interface was investigated by measuring its surface tension. The number of particles retained was determined stereologically. In addition we investigated the displacement of spherical particles in vitro on a DPPC monolayer in a Langmuir-Wilhelmy surface balance and determined the surface tension in vivo in the horse trachea by video bronchoscopy, applying the droplet spreading method. We found that particles deposited onto a surfactant film were pulled into the aqueous subphase, and we concluded that surface forces due to the airway surfactant likely displace deposited particles into the periciliary fluid (sol phase). Comparing lungs fixed immediately after inhalation with lungs fixed 24 hr after inhalation revealed that 86% of the particles retained in the intrapulmonary conducting airways immediately after inhalation had been cleared within 24 hr. One-third of the particles of the lungs fixed immediately after inhalation was phagocytized. The combination of structural and stereological analyses with in vitro and in vivo measurements has led to new insights into the role of airway surfactant with respect to the fate of inhaled particles, which may have important consequences regarding the effects of hazardous particles. These studies may also help to evaluate the deposition pattern and clearance of therapeutic particles, with important implications for their therapeutic use.

Administration, Inhalation↗
PubMed1993

[Forgotten expertise about chiropractic].

Two forgotten experts on chiropractic are revived to expose the lack of scientific foundation of osteopathy, chiropractic and manual medicine. It is reemphasized that for the majority of patients with back complaints a precise and tangible pathologic finding explaining the pain can not be established. Likewise the correlation between radiologic, tomographic and patho-anatomic alterations with the patients complaints leaves much to be desired, particularly for the spinal column. Back ailments plagued humanity already in ancient times, their crippling effects seem, however, to be of iatrogenic origin originating in the 20th century. To explain the success stories of manual healers it is important to distinguish between medical science and the actions of the healer.

Chiropractic↗
PubMed1993

[Whiplash injury--a confusing concept].

The functional anatomy of the cervical spine, the biomechanics of lesions due to rear end collisions, the human behaviour of victims of these collisions and the influence of insurance, legislation, court decisions and the modalities and duration of treatment are discussed in a survey of the literature on lesions of the cervical spine due to rear end collisions. The problems posed by changed court rulings on lesions of the cervical spine due to rear end collisions are mentioned, as well as the danger of producing a "whiplash" compensation epidemic. It appears that immediate treatment of the lesion avoiding manipulation, long immobilization and delay in decisions on compensation may reduce the frequency, intensity and duration of symptoms. The symptoms usually remit after settlement of compensation and seldom give rise to substantial disability. The prevention of lesions of the cervical spine and head due to rear end collisions will only be possible if car safety engineers succeed in preventing rear end collisions and/or in ending hyperextension by appropriate devices. The head supports in use today are not sufficient to prevent hyperextension of the cervical spine.

Automobiles↗
PubMed1993

Immunologically unrelated Heliothis sp. and Spodoptera sp. midgut membrane-proteins bind Bacillus thuringiensis CryIA(b) delta-endotoxin.

The Bacillus thuringiensis toxins, CryIA(a), CryIA(b), CryIA(c) and CryIC were used in a ligand-blot assay to detect specific toxin-binding proteins in the brush-border membranes of Heliothis virescens, Helicoverpa zea, Spodoptera littoralis, Spodoptera exigua and Spodoptera litura. While CryIA(a) and CryIA(b) always recognize the same protein(s) in a given species, CryIA(c) and CryIC were found to bind to other proteins. Polyclonal antibodies directed against the CryIA(b) binding protein of H. virescens and polyclonal anti-idiotype antibodies recognizing some determinants of the CryIA(b)-binding protein involved in the interaction with the toxin, were used to analyse immunological relationships among the toxin-binding proteins. The results showed that the 170-kDa toxin-binding proteins from the H. virescens and H. zea are immunologically related. However, the toxin-binding proteins from the Spodoptera species did not cross-react with either type of antibodies. Therefore, we conclude that the CryIA(b) toxin has different binding determinants on the toxin molecules itself which can interact with specific binding sites on the toxin-binding proteins from Heliothis sp. and Spodoptera sp.

Animals↗
PubMed1991

Identification and characterization of Heliothis virescens midgut membrane proteins binding Bacillus thuringiensis delta-endotoxins.

To investigate the specificity of Bacillus thuringiensis var. kurstaki strain HD1 insecticidal crystal proteins (ICP), we used membrane preparations obtained from the midgut of Heliothis virescens larvae to perform separate ligand-blot experiments with the three activated CryIA toxins. The CryIA(a) and the CryIA(b) toxins bind the same 170-kDa protein, but most likely at two different binding sites. The CryIA(c) toxin binds two proteins of molecular masses 140 kDa and 120 kDa. We also demonstrate that the binding proteins for each of the B. thuringiensis toxins are not part of a covalent complex. Although the 170-kDa protein is a glycoprotein, endoglycosidase treatment does not prevent the binding of the CryIA(a) or CryIA(b) toxin. This indicates that the sugars are not important for the binding of these toxins. A model for a protein complex binding the B. thuringiensis HD1 ICPs is presented. Our results support the idea that binding proteins on membranes of the gut epithelial cells of H. virescens larvea are important for the specificity of the bacterial toxins.

Animals↗
PubMed1990

[Particle retention in the intrapulmonary conducting airways in hamsters].

Inhalation and the subsequent deposition, retention and clearance of particles play a pivotal role in pulmonary medicine. It has been widely accepted that inhaled insoluble particles which are deposited in the conducting airways are largely cleared within 24 hours by the mucociliary escalator. Recent reports, however, suggest that this view should be revised. We therefore investigated by light and electron microscopy the number and location of particles retained in the intrapulmonary conducting airways of hamsters as a function of time. The number of retained particles was estimated unbiasedly with a novel stereological method, the fractionator. Seven male Syrian Golden hamsters inhaled an aerosol of 6 microns polystyrene particles under controlled conditions. The lungs of 3 animals were fixed by intravascular perfusion 20 minutes after the inhalation, whereas those of the other 4 animals were fixed 24 hours later. Retained particles were found in all generations of the intrapulmonary conducting airways. They were submerged in the extracellular matrix in close contact with the epithelial cells between the cilia. The particles were coated by a thin layer of osmiophilic material which was interpreted as surfactant. In the lungs fixed immediately after the inhalation, 36% of the retained particles were ingested by macrophages. 24 hours after inhalation we still found 14% of the initially retained particles. 90% of these remaining particles were phagocytized. We conclude that: (1) Surfactant is important for the retention of particles in the intrapulmonary conducting airways of hamsters. (2) There is evidence for the existence of a resident population of very active airway macrophages which play a pivotal role in clearance of the retained particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants↗
PubMed1990

Surfactant displaces particles toward the epithelium in airways and alveoli.

This study was designed to investigate the early stages of particle deposition on airway and alveolar surfaces. To do this we used morphometric studies of aerosol deposition, in situ measurements of surface tension, and in vitro assays of particle displacement and mathematical modelling. We observed that latex particles, equal or less than 6 microns in diameter deposited in hamster lungs were submerged in the subphase of the alveolar lining layer and became completely coated with an osmiophilic film. Similar results were obtained for particles deposited in the conductive airways which were also covered with a surface active film, having a surface tension of 32 +/- 2 dyn.cm-1. In vitro experiments showed that pulmonary surfactant promotes the displacement of particles from air to the aqueous phase and that the extent of particle immersion depends on the surface tension of the surface active film. The lower the surface tension the greater is the immersion of the particles into the aqueous subphase. Mathematical analysis of the forces acting on a particle deposited on an air-fluid interface show that for small particles (less than 100 microns) the surface tension force is several orders of magnitude greater than forces related to gravity. Thus, even at the relatively high surface tension obtained in the airways (32 +/- 2 dyn.cm-1) particles will still be displaced into the aqueous subphase. Particles in peripheral airways and alveoli likely are below the surfactant film and submerged in the subphase. This may promote clearance by macrophages. In addition, particle displacement into the subphase is likely to increase the contact between the epithelial cell and particle. Toxic or allergenic particles would be available to interact with epithelial cells and this may be important in the pathophysiology of airway disease.

Administration, Inhalation↗
PubMed1990

Assessment of particle retention and clearance in the intrapulmonary conducting airways of hamster lungs with the fractionator.

A modified version of the fractionator was used to estimate the total number of polystyrene microspheres retained in the airways of hamster lungs at two different time points after inhalation. A systematic three-stage subsampling procedure with known sampling fractions was adopted. First, each lung was cut into slices, from which primary disectors were sampled systematically with a known sampling fraction. From each primary disector, smaller sub-disectors were subsampled, and the corresponding sampling fraction was estimated by point counting. Finally, a few particles were counted at the microscopic level in the sub-disectors, and the final estimate of total particle number (which is unbiased irrespective of any tissue deformations) was easily computed as a product of the counted number times the reciprocal of the successive sampling fractions. The error variance of each estimate was assessed from the data using a new estimator. An average of 6% of the deposited particles were retained on the epithelial surface of the intrapulmonary conducting airways shortly after the inhalation, from which at least one-third was already phagocytosed by macrophages. After 24 h, an average of 87% of the particles retained shortly after the inhalation had been cleared. The proportion of particles ingested by macrophages had increased to at least 87% in three out of four animals studied.

Animals↗
PubMed1989

Efficient transformation of Bacillus thuringiensis and B. cereus via electroporation: transformation of acrystalliferous strains with a cloned delta-endotoxin gene.

Electroporation was used as a method to transform intact cells of Bacillus thuringiensis and B. cereus. With our optimized method a range of plasmid vectors could be transformed into strains of B. thuringiensis at frequencies of up to 10(7) transformants/micrograms DNA. This high frequency allows cloning experiments to be done directly in B. thuringiensis. A bifunctional vector capable of replicating in Escherichia coli and in Bacillus spp. was constructed. The kurhd1 protoxin gene was cloned into this shuttle vector to produce plasmid pX193, then transformed into B. thuringiensis HD1 cryB and B. cereus 569K. The cloned protoxin gene was expressed in sporulating cultures of both strain HD1 cryB (pX193) and 569K (pXI93), producing crystal protein active in biotests against larvae of Heliothis virescens. This demonstrates the usefulness of the electroporation method for the introduction of cloned toxin genes, in either their native or modified form, into a variety of host strains.

Bacillus cereus↗
PubMed1988

Value of computed tomography in the staging of testicular tumors.

To analyze the value of computed tomography (CT) for the exact staging of testicular tumors, 2 groups of 28 patients each were examined. All patients underwent retroperitoneal lymph node dissection in the course of their treatment. Pretherapeutic stages as determined by CT were compared to the histologically verified definite tumor stages. In 68% of the patients, the stage found by CT was correct but 3 (5%) false-positive and 13 false-negative results were obtained. Thus, almost 40% (13/33) of the patients with clinical stage I disease presumably would have had a progression if managed by a surveillance strategy. It can be concluded that this strategy should be restricted to certain centers with guaranteed long-term standardized patient observation and extremely high patient compliance.

Dysgerminoma↗