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Biomedical subjects

M Hauser

Publications and source records attributed to M Hauser.

At least 127 records · Page 7Linked to original sources
PubMed1988

The effects of drugs on the formation of Theileria annulata merozoites in vitro.

The effects of colchicine, taxol, dinitrophenol, sodium azide, TLA-144, and obioactin on Theileria annulata schizonts were tested in vitro and studied by means of light and electron microscopy. Colchicine (0.001-5 microM) and taxol (1 microM) completely inhibited the mitosis of the host cell. This resulted in higher numbers of schizont nuclei after 96 h, since the division of the parasites was apparently not affected. Increasing numbers of schizont nuclei were also obtained after incubation of parasitized lymphocytes for 7 day at 41 degrees C with a daily medium exchange.

Alkaloids↗
PubMed1987

Age-dependent changes in fluorescent neurons in the brain of Notoplana acticola, a polyclad flatworm.

The formaldehyde-glutaraldehyde-sucrose (FGS) method for in situ localization of catecholamines has been applied to the nervous system of the marine polyclad flatworm Notoplana acticola. This histochemical fluorescence technique revealed the presence of a small population of fluorescent cells within the brain. The number and positions of these neurons were constant in animals of the same size, but varied with the size of the worm. The brains of small animals (8 mm in length) were found to contain 20 fluorescent cells, whereas the largest animals studied (30 mm in length) were found to have 28 such cells. Various intermediate cell numbers were found in animals between these two sizes. The origin of the newly added fluorescent cells is uncertain. Peripheral fluorescence was found in association with the tentacular ocelli (eyespots) and interneurons within the ventral submuscular nerve plexus. The fluorescent spectrum from these cells measured in situ had a lambda max of 526 nm. Treatment with HCl shifts this peak to 530 nm. L-dopamine fluoresces with a similar peak emission before HCl treatment (525.5 nm) and shifts to the appropriate longer wavelength (530 nm) following acidification. This strongly suggests that the fluorescent substance in the neurons is dopaminergic in nature.

Aging↗
PubMed1986

Studies of enzyme-ligand complexes using dynamic fluorescence anisotropy. II. The coenzyme-binding site of malate dehydrogenase.

The coenzyme-binding site in mitochondrial malate dehydrogenase from pig heart was studied using dynamic fluorescence anisotropy decay. The dynamics of the fluorescent ligands NADH and 6-cyano-7-hydroxy-4,8-dimethylcoumarin were used to detect conformational changes at the dihydronicotinamide-and at the adenosine-binding sites, respectively. Addition of the natural substrate L-malate to the complex from enzyme and NADH does not influence the complete immobilization of the dihydronicotinamide group, whereas the stereoisomer D-malate and the substrate-analogue hydroxymalonate form ternary complexes with highly mobile dihydronicotinamide. The dynamics of the fluorescent adenosine-analogue are not influenced by formation of complexes with substrate and substrate-analogues. Thus the conformational changes at the dihydronicotinamide-binding site remain local and are not transmitted to the adenosine-binding site.

Adenosine↗
PubMed1986

Studies of enzyme-ligand complexes using dynamic fluorescence anisotropy. I. The substrate-binding site of malate dehydrogenase.

The substrate binding site of pig mitochondrial malate dehydrogenase was characterized using complexes of the enzyme with the substrate analogue 8-hydroxypyrene-1,3,6-trisulfonate with and without the addition of coenzymes. The rotational mobility of the fluorescent dye within the binding site was examined with the aid of a multi-frequency phase-fluorimeter. Together with absorption, circular dichroism and fluorescence spectroscopy, conformational changes of the substrate binding site could be defined. The dye was generally found to be immobilized in the binding site. Addition of NADH to the binary complex caused strengthening of a hydrogen bond and further loss of mobility, whereas NAD enlarged the space available for motion of the dye with concomitant loss of the hydrogen bridge.

Animals↗
PubMed1986

Taxol affects both the microtubular arrays of heliozoan axonemes and their microtubule-organizing center.

Short and long-term effects of the antitumor drug taxol on the microtubular axonemes and on the microtubule-organizing centroplast of the centrolhelidian Heterophrys marina have been investigated. Short-term treatment reveals that general aspects of cell structure remain substantially unaffected and that additional microtubule (MT) assembly in individual axonemes is accompanied by disassembly in others. However, the interaction between MTs, via cross-bridging associated proteins, is seriously affected as indicated by the numerous softly-bent axopods with disturbed arrays of the normally hexagonal pattern. Stabilization of MTs becomes evident by the reexpansion of axopods during low temperature incubation and also by the rapid inhibition of the saltatory movement of the extrusive organelles. Rapidly reexpanding axonemes of cells incubated at higher temperatures and in high taxol concentrations arise asymmetrically from the microtubule-organizing centrosomal structure (centroplast) and form a single thick and thorn-like axopodium, indicating a certain disarrangement of the centrally located microtubule-organizing center (MTOC), which obviously is severely damaged after long-term treatment. With increasing disorganization of the centroplast's structure, these cells reveal themselves unable to sustain their regular microtubular axonemal cytoskeleton. Paradoxically, polymerization of free microtubules from the tubulin pool does not take place. Instead, paracrystalline arrays of twisted filaments appear within the cytoplasm. It is concluded that heliozoan MTs can only persist if stabilized by additional factors, such as permanent interaction with the intact centroplast, and that even in the presence of taxol, MTs unattached to such an MTOC will be intrinsically unstable.

Alkaloids↗
PubMed1984

Impaired natural killer cell function in hemophiliacs with or without continuous substitution.

In the present study, 28 hemophiliacs substituted continuously and 5 hemophiliacs who had received almost no blood products were investigated. Cells of OKT 3+, OKT 4+, and OKT 8+ subsets were counted. Percoll separated fractions of peripheral blood mononuclear cells were examined by morphological criteria and were tested for NK cell activity. We found that the NK cell activity of both groups of hemophiliacs was decreased on testing Ficoll separated cells or low density Percoll separated cells. Normal NK cell activity was found in medium density cells of hemophiliacs. Two possible explanations are discussed: first, the NK cell activity may be suppressed in hemophiliacs and secondly, there may be a block in maturation of NK cell activity. It is unlikely that chronic substitution by blood products counts for these alterations. The possible role of chronic infections is discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Transrectal real-time ultrasound scanning of the cow reproductive tract.

A transrectal real-time ultrasound scanning of the cow reproductive tract allows the operator to view images of structures which normally can be only palpated. The device used in these studies allowed exact evaluation of the cow reproductive tract for position, size and consistency of ovaries, uterus and fetuses; these parameters cannot be described to this level of exactness even by the most skilled palpators. This paper describes real-time ultrasound scanning of an ovary containing a cystic corpus luteum and several follicles and ofa nonpregnant and a pregnant tract at different stages of gestation. The device may be expected to aid both the researcher and the practicing veterinarian considerably in the future.

Journal Article↗
PubMed1982

Electron microscopic localization of ATPase activity in the cytopharyngeal basket of the ciliate Pseudomicrothorax dubius.

The cytopharyngeal basket of Pseudomicrothorax dubius is used to ingest filamentous blue-green algae. The basket has three main components: a sheath of microfilaments, bundles of microtubules (the nemadesmata), and ribbons of microtubules. The ribbons of microtubules (nemadesmal lamellae) are adpressed to the food vacuole during ingestion. Cytochemical techniques show that both the lamellae and the microfilamentous sheath possess ATPase activity, but the reaction product appears under different conditions in the two cases. The presence of ATPase activity within the microtubular lattices of the feeding organelle suggests the capacity for active motility. Consequently the basket seems to have two motile systems, one may be used to constrict and dilate the cytopharynx while the other is used in the inward propulsion of the forming food vacuole.

Adenosine Triphosphatases↗
PubMed1980

Comparison of measured and calculated colloid osmotic pressure of serum and pulmonary edema fluid in patients with pulmonary edema.

Serum and pulmonary edema fluid samples of 26 patients with pulmonary edema were examined. The correlation coefficient comparing measured colloid osmotic pressure (COPm) to calculated colloid osmotic pressure (COPc) (Landis and Pappenheimer equation) was 0.84. Significant differences between COPm and COPc were noted when total protein (TP) concentrations were less than or greater than 5 g/dl (p < 0.001 and p < 0.01, respectively). Twenty-one of 69 samples (30%) had a greater than 4 mm Hg difference between measured and calculated values. COP should be measured rather than calculated for accurate determinations.

Adult↗
PubMed1979

Helically twisted filaments in giant neurons of a whip spider.

In giant neurons of whip spider legs several filament types are detectable: filaments of 5 to 6 nm thickness as dense masses within the soma of the neuron, an intermediate-sized filament type limited to the dendritic processes forming irregularly wound bundles and finally twisted double filaments in the soma as well as in peripheral regions. The latter are usually aggregated in paracristalloid lattices of different length and diameter.

Animals↗
PubMed1978

Demonstration of membrane-associated and oriented microfilaments in Amoeba proteus by means of a Schiff base/glutaraldehyde fixative.

After fixation with a reaction product of glutaraldehyde and spermidine phosphate Amoeba proteus cells show a network of cortical microfilaments and oriented bundles of thick and thin filaments. The cortical filament network appears to be membrane-attached and extends beneath the whole cytoplasmic membrane surface. In the uroid region and in retracting pseudopods the cortical layer is thicker than in advancing cell regions. The filament bundles are located predominantly in the ectoplasmic tube within the cortical network. They strictly parallel the cell surface contours.

Amoeba↗
PubMed1976

Microtubules and associated microfilaments in the tentacles of the suctorian Heliophrya erhardi Matthes.

At the ultrastructural level length changes accompanying linear movements of resting (non-feeding) tentacles of the suctorian Heliophrya involve not only altered microtubule numbers, but also marked changes in the specific microtubule pattern of cross-sectioned tentacles. These changes in number and pattern indicate a sliding between axonemal microtubules. The visualization of microfilaments in the cytoplasm at the tentacle base and in the knob region could shed new light on the problem of whether microtubular sliding is an active or passive process. At the tentacle base, microfilaments are either arranged in a ring-shaped configuration around the axoneme, or they run parallel to the axonemal microtubules, whereas at the tentacle tip during the resting state, microfilaments are closely associated with the plasma membrane of the knob. They form a filamentous reticular layer, which is continuous at the anchorage site of axonemal microtubules with the dense epiplasmic layer of the tentacle shaft. Obiously, this filamentous layer is engaged in positioning the haptocysts at the plasma membrane and in holding the membrane itself under tension. The putative contractile nature of microfilaments and the epiplasmic layer is argued from ATP-sensitive glycerol models of tentacles and from the results of halothane treatment of native tentacles. Halothane treatment of resting tentacles also gave indications of the presence of differentially stable intermicrotubule-bridges. The role of micro-filaments and halothane-resistant dynein-like inter-row bridges in tentacle movement is discussed. As soon as the plasma membrane of the knob is 'sealed' with the prey pellicle during feeding, the microtubules of the sleeve region slide into the knob where they bend back and outwards. The microtubules now appear decorated and sometimes cross-connected by microfilaments which adhere closely to the plasma membrane- now acting as a peritrophic membrane-lining the prey cytoplasm against the microtubules of the inner tube. These microfilaments which show a close association with the microtubules of the active knob area, are thought to be engaged in microtubular bending and stretching during feeding. They may also be involved in the transport of the peritrophic membrane in distal tentacle regions. Microinematographically recorded oscillations in tentacle diameter in these regions are in agreement with the electron-microscopic findings of various states of collapsed tentacle axonemes. These observations, as well as the occurrence of helically twisted tentacles during feeding, suggest microfilament mediated sequential back and forth movements of sleeve microtubules in the knob region which generate a proximally migrating helical wave.

Adenosine Triphosphate↗