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Biomedical subjects

R D Allen

Publications and source records attributed to R D Allen.

At least 163 records · Page 9Linked to original sources
PubMed1986

Analysis of antibodies against mouse spermatozoa using an enzyme-linked immunosorbent assay (ELISA).

Conventional techniques used for the analysis of antisperm antibodies are not suited to the mouse model because of their requirements for relatively large amounts of serum and their inability to handle large numbers of samples. This has inhibited use of the mouse as an experimental model in areas involving antisperm immunity. As the ELISA technique has been successfully applied to analysis of antisperm antibody in human sera, we investigated its use as an assay for screening antisperm antibody in mouse serum. This report describes a simplified version of the ELISA technique that we have found to be successful for this purpose. The assay described can assess levels and classes of antisperm antibody in mouse serum and can also be used as a screening assay for monoclonal antibodies to mouse sperm. It should facilitate use of the mouse in experimental work in areas involving assessment of immunity to sperm.

Animals↗
PubMed1986

The relationship between the immunosuppressive and cytotoxic effects of human seminal plasma.

This report describes the cytotoxic properties of human seminal plasma and demonstrates that the inhibition of response to mitogens shown by murine lymphocytes in the presence of whole human seminal plasma can be attributed largely to an effect of seminal components on lymphocyte viability. It is hypothesised that the cytotoxic effect of seminal plasma arises as a result of the oxidation of spermine in seminal plasma by an amine oxidase enzyme present in fetal calf serum. In support of this hypothesis, it was found that seminal plasma cytotoxicity is serum dependent and is inhibited in the presence of the amine oxidase inhibitor hydroxylamine.

Amine Oxidase (Copper-Containing)↗
PubMed1985

Flow birefringence of microtubules and its relation to birefringence measurements in cells.

Understanding the molecular basis of mitotic movements in living cells will require correlative experiments on intact cells, cell models, purified tubulin, and perhaps other biopolymers. Birefringence is one assay that is useful in all of these experimental situations. Heretofore, studies of birefringence changes during mitosis have lacked a quantitative basis for interpretation in terms of microtubule number and packing density. One of the aims of this work was to establish that relationship. Purified calf brain tubulin was polymerized to equilibrium and oriented in the hydrodynamic field of a microcapillary flow birefringence apparatus. The relationship between birefringence and microtubule packing density was determined by a combination of optical, electron microscopic, and biochemical methods. The data correlate surprisingly well with those obtained by others from in vitro measurements on isolated mitotic spindles. Using the flow birefringence data, the sensitivity of polarizing microscopes for detecting microtubules was examined and found to depend on microtubule packing density, object thickness, and instrumental factors that limit both the detection and measurement of weakly birefringent objects. Because of the dependence of measurement sensitivity on object thickness, a method of measuring the thickness of microtubule bundles using the dispersion of birefringence was developed. This method is capable of measuring thickness to within two or three Airy diffraction units and does not require any assumptions regarding object symmetry.

Animals↗
PubMed1985

Video microscopy of fast axonal transport in extruded axoplasm: a new model for study of molecular mechanisms.

The development of AVEC-DIC microscopy and the application of this method to the study of fast axonal transport in isolated axoplasm extruded from the giant axon of the squid Loligo pealei provides a new paradigm for analyzing the intracellular transport of membranous organelles. The size of the axon, the number of transported particles, and the absence of permeability barriers like the plasma membrane in this preparation permit many experiments that are difficult or impossible to perform using other model systems. The use and features of this preparation are described in detail and a number of properties are evaluated for the first time. The process of extrusion is characterized. Particle movement is evaluated both in the interior of extruded axoplasm and along individual fibrils that extend from the periphery of perfused axoplasm. The role of divalent cations, particularly Ca2+, and the effects of elevated Ca2+ on axoplasmic organization and transport are analyzed. A series of pharmacological agents and polypeptides that alter cytoskeletal organization are used to examine the role of microfilaments and microtubules in fast transport. Finally, the effects of depleting ATP and of adding ATP analogues are discussed. The extruded axoplasm preparation is shown to be an invaluable model system for biochemical and pharmacological analyses of the molecular mechanisms of intracellular transport.

Adenosine Triphosphate↗
PubMed1985

Gliding movement of and bidirectional transport along single native microtubules from squid axoplasm: evidence for an active role of microtubules in cytoplasmic transport.

Native microtubules prepared from extruded and dissociated axoplasm have been observed to transport organelles and vesicles unidirectionally in fresh preparations and more slowly and bidirectionally in older preparations. Both endogenous and exogenous (fluorescent polystyrene) particles in rapid Brownian motion alight on and adhere to microtubules and are transported along them. Particles can switch from one intersecting microtubule to another and move in either direction. Microtubular segments 1 to 30 microns long, produced by gentle homogenization, glide over glass surfaces for hundreds of micrometers in straight lines unless acted upon by obstacles. While gliding they transport particles either in the same (forward) direction and/or in the backward direction. Particle movement and gliding of microtubule segments require ATP and are insensitive to taxol (30 microM). It appears, therefore, that the mechanisms producing the motive force are very closely associated with the native microtubule itself or with its associated proteins. Although these movements appear irreconcilable with several current theories of fast axoplasmic transport, in this article we propose two models that might explain the observed phenomena and, by extension, the process of fast axoplasmic transport itself. The findings presented and the possible mechanisms proposed for fast axoplasmic transport have potential applications across the spectrum of microtubule-based motility processes.

Animals↗
PubMed1985

Identification and characterization of latex-specific proteins in opium poppy.

Latex from the opium poppy, Papaver somniferum L., was analyzed by polyacrylamide gel electrophoresis (PAGE). Two latex-specific bands were identified in protein samples of poppy latex using one-dimensional native PAGE. Second dimension analysis with SDS-PAGE indicates that these proteins have a relative molecular weight of approximately 20 kilodaltons. We have termed these polypeptides the major latex proteins (MLPs). Polyclonal antibodies prepared against the MLPs were used to probe protein gel blots of latex and poppy tissues known to lack laticifers. Laticifer-free tissues showed no reaction with anti-MLP immunoglobulin G indicating that MLPs are found only in poppy latex. MLP distribution was also examined in mature opium poppy tissues by immunocytochemistry. Laticifers were differentially labeled by fluorescein isothiocyanate secondary labeling of anti-MLP immunoglobulin G and could easily be identified in both transverse and longitudinal section. Fractionation studies of isolated latex showed that MLPs are concentrated in the latex cytosol and not in alkaloidal vesicles. Analysis of latex proteins by conventional two-dimensional electrophoresis indicates that the two MLP bands are composed of several distinct polypeptides with similar relative molecular weights. The pIs of these molecules range from 6.0 to 3.5. The role(s) of MLPs in laticifer metabolism has not been determined.

Journal Article↗
PubMed1985

Laser scanning phase modulation microscope.

We describe the concept and first implementation of an innovative new instrument for quantitative light microscopy. Currently, it provides selective imaging of optical path differences due to birefringence; with further development, it is also possible to selectively image several optical properties, including refractive path differences, optical rotation, and linear and circular dichroism, all with diffraction-limited resolution. An image consists of a 512 X 512 element array, with each pixel displaying one of 256 grey levels, linearly proportional to the specific optical property being observed. Additionally, conventional brightfield and polarized light microscopy are available, with the accompanying advantages of laser scanning and digital image processing. The microscope consists of three subsystems, representing three distinct technologies. The laser scanning subsystem moves a focused microspot across the specimen; the output of a photodetector is an electric signal corresponding to a scanned image. The image display subsystem digitizes this signal and displays it as an image on a video monitor. When used in conjunction with a phase modulation feedback loop, the image formed is of the specimen's birefringent retardation or other selected optical property. The digitized images are also available for computer enhancement.

Animals↗
PubMed1985

Modulation of the digestive lysosomal system in Paramecium caudatum. II. Physiological effects of cytochalasin B, colchicine and trifluoperazine.

The heterophagic pathway of the digestive lysosomal system in Paramecium caudatum includes at least four steps: digestive vacuole (DV) formation, acidification-condensation, lysosomal fusion-digestion, and defecation. The second and the third require about 20 min, during which DVs are not egested. Because these steps occur at predictable intervals, the mechanism for each can be explored by exposing labeled DVs to different drugs prior to each step. In this study the effects of cytochalasin B (CB), colchicine and the calmodulin antagonist, trifluoperazine (TFP), were studied. All three drugs inhibited DV formation in a dose-dependent manner when cells were pulsed with latex beads and a drug simultaneously. TFP was cytotoxic above 5 microM. Vacuole formation was completely shut down when cells were pre-exposed to 5 microM TFP for 13 min. At this level, the duration of the acidification step was lengthened, and the rate of defecation decreased with increasing exposure. These results suggest that these inhibitory effects may be more related to TFP's cytotoxicity than to its action on calmodulin-mediated process. Colchicine at 1 mM had no effect on the third or fourth step, but inhibited the acidification step so that DVs were egested later and at a slower rate. Exerting a differential effect on all four steps, CB inhibited DV release from the cytopharynx, egestion of defecation-competent DVs at the cytoproct and lengthened the duration but did not block the lysosomal fusion-digestion step of the acidic DVs; it was most potent in blocking acidification, which prevented both lysosomal fusion with the labeled DVs as well as DV egestion, the latter for more than 50 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Modulation of the digestive lysosomal system in Paramecium caudatum. III. Morphological effects of cytochalasin B.

Morphological explanations for the effects of cytochalasin B (CB) on the digestive vacuole system of Paramecium caudatum were sought using electron-microscopic studies. Cytochalasin B (0.3 mM) essentially stopped vacuole release without stopping vacuole growth. Acidosome fusion with the new vacuoles was inhibited and was accompanied by the formation of discoidal vesicle-lined clumps of microfilament-like material next to these vacuoles. Vacuole membrane retrieval at the open cytoproct was inhibited and was accompanied by the loss of the microfilament network typical of this region. At 0.15 mM CB vacuole release and fusion of the acidosomes and lysosomes with the vacuoles were not stopped, but membrane retrieval at the cytoproct was affected. Cytochalasin B at the higher concentration also affected the movement of the horseradish peroxidase (HRP)-labeled vesicles away from the nascent vacuole. Membrane retrieval by the formation of tubules of 35 to 50 nm diameter from membrane of early and late vacuole stages was also affected by CB. It is conceivable that all of these effects were the result of the disruption of membrane associated actin networks. By contrast, several highly organized microfilamentous systems in the cortex and oral region of these cells appeared to be unaffected by CB or dimethyl sulfoxide (DMSO) at the concentrations used. These results show that CB-susceptible structures assume a key role in the normal functioning of the digestive vacuole system and in vacuole membrane retrieval and reutilization in Paramecium.

Animals↗