Scanning electron microscopy of the myosin-coated surface of polystyrene beads in a force-movement assay system for ATP-dependent actin-myosin sliding

An outbreak of Cryptosporidiosis occurred over three months in a British Columbia community, peaking in December 1990. Results of the case-control study and illness surveys support the hypothesis that transmission occurred in a public children's pool at the local recreation centre. Analysis using lab-confirmed cases revealed a matched odds ratio of 4.5 [95% CI 0.97, 20.83], and using clinical cases an unmatched odds ratio of 12.8 [95% CI 3.68, 46.77], associated with swimming in the children's pool within two weeks prior to onset of illness. Other risk factors were not significant. Attack rates in various groups of children's pool users ranged from 8% to 78%. The children's pool was closed for steam cleaning and disinfection. Unusually frequent defecations including liquid stools had occurred before and during the outbreak. Improvements were instituted for removal of feces and superchlorination of pool water.     

Assembly and function of the actin cytoskeleton of yeast: relationships between cables and patches

Actin in eukaryotic cells is found in different pools, with filaments being organized into a variety of supramolecular assemblies. To investigate the assembly and functional relationships between different parts of the actin cytoskeleton in one cell, we studied the morphology and dynamics of cables and patches in yeast. The fine structure of actin cables and the manner in which cables disassemble support a model in which cables are composed of a number of overlapping actin filaments. No evidence for intrinsic polarity of cables was found. To investigate to what extent different parts of the actin cytoskeleton depend on each other, we looked for relationships between cables and patches. Patches and cables were often associated, and their polarized distributions were highly correlated. Therefore, patches and cables do appear to depend on each other for assembly and function. Many cell types show rearrangements of the actin cytoskeleton, which can occur via assembly or movement of actin filaments. In our studies, dramatic changes in actin polarization did not include changes in filamentous actin. In addition, the concentration of actin patches was relatively constant as cells grew. Therefore, cells do not have bursts of activity in which new parts of the actin cytoskeleton are created.     

Tropomyosin-containing actin cables direct the Myo2p-dependent polarized delivery of secretory vesicles in budding yeast

The actin cytoskeleton in budding yeast consists of cortical patches and cables, both of which polarize toward regions of cell growth. Tropomyosin localizes specifically to actin cables and not cortical patches. Upon shifting cells with conditionally defective tropomyosin to restrictive temperatures, actin cables disappear within 1 min and both the unconventional class V myosin Myo2p and the secretory vesicle-associated Rab GTPase Sec4p depolarize rapidly. Bud growth ceases and the mother cell grows isotropically. When returned to permissive temperatures, tropomyosin-containing cables reform within 1 min in polarized arrays. Cable reassembly permits rapid enrichment of Myo2p at the focus of nascent cables as well as the Myo2p- dependent recruitment of Sec4p and the exocyst protein Sec8p, and the initiation of bud emergence. With the loss of actin cables, cortical patches slowly assume an isotropic distribution within the cell and will repolarize only after restoration of cables. Therefore, actin cables respond to polarity cues independently of the overall distribution of cortical patches and are able to directly target the Myo2p-dependent delivery of secretory vesicles and polarization of growth.     

Modification of the bi-directional sliding movement of actin filaments along native thick filaments isolated from a clam

A reliable viability assay for Giardia is required for the development of disinfection process design criteria and pathogen monitoring by water treatment utilities. Surveys of single-staining nucleic acid dyes (stain dead parasites only), and double-staining vital dye kits from Molecular Probes (stain live and dead parasites) were conducted to assess the viability of untreated, heat-killed, and chemically inactivated Giardia muris cysts. Nucleic acid staining results were compared to those of in vitro excystation and animal infectivity. Nucleic acid stain, designated as SYTO-9, was considered the best among the single-staining dyes for its ability to stain dead cysts brightly and its relatively slow decay rate of visible light emission following DNA binding. SYTO-9 staining was correlated to animal infectivity. A Live/Dead BacLight was found to be the better of 2 double-staining viability kits tested. Logarithmic survival ratios based on SYTO-9 and Live/Dead BacLight were compared to excystation and infectivity results for G. muris cysts exposed to ozone or free chlorine. The results indicate that SYTO-9 and Live/Dead BacLight staining is stable following treatment of cysts with chemical disinfectants.     

Insolubilization of protein antigens on polyacrylic plastic beads using poly-L-lysine

A new model system for quantitation of immunofluorescence on single cells is described using poly-L-lysine (PLL) coated polyacrylic plastic beads of approximately cell sizes as carriers for protein antigen. By increasing PLL concentration on the beads increased amounts of 125I labeled antigen were attached to the particles. Excess binding sites of PLL could be completely blocked by unrelated proteins. After staining with FITC-conjugated antibodies and quantitative fluorescence measurements of individual beads using a microspectrofluorimeter, strong correlations were found between antibody and antigen concentration on the beads. Neither repeated washings with PBS nor storage of the beads for two months caused detectable shedding of antigen-antibody complexes. There was a strong linear correlation between fluorescence intensity and the volume of beads, but the correlation between surface area and fluorescence was nonlinear. The described procedure was shown to be a simple method for quantitative and stable coating of particles with proteins. It can be applied as a useful model system for quantitative immunofluorescence studies on intracellular antigens.     

Effect of periodic "head-foot" G-forces in a short-radius centrifuge on human cardiovascular system responses

During 3- and 6-day immersion studies test subjects were two or three times a day (60 min each time) exposed to head-to-feet acceleration of 1-2 G in a 2 m arm centrifuge. In 297 runs cardiovascular reactions were compared with respect to their adaptation or cumulation. The results showed that the principle of periodic application of acceleration in a short-arm centrifuge as a countermeasure against cardiovascular deconditioning can be complemented by the principle of cyclic exposures. The study demonstrated that 3-day cycles including 60 min exposures to 1-2 Gz twice a day were most efficient.     

Study of aseptic inflammation using the scanning electron microscope

A focus of inflammation in the subcutaneous connective tissue in white rats was investigated in a scanning electron microscope. Lymphocytes, polyblasts, macrophages, fibroblasts, collagenous fibres, gigantic multinuclear cells, vessels are described. Similiarity in the form and structure of the surface in agranulocytes of the blood, polyblasts and macrophages was established. A considerable change in morphology of fibroblasts, particularly in the period of synthesis os of the cell, was observed. Collagenous fibres and fibroblasts played a leading role in the creation of the supporting-mechanical carcass and in spatial structure of the regenerating connective tissue.     

Reconstruction of the lateral ligaments of the ankle using a regional periosteal flap

We have treated 94 patients with chronic instability of the lateral side of the ankle by reconstruction of the ligaments with local periosteal tissue. We reviewed 90 cases after a mean follow-up of 2.8 years (2 to 9) using a questionnaire, clinical examination and radiography. The results on a 100-point ankle score indicated that 81% had a good or excellent result. The periosteal flap-replacement technique allows anatomical reconstruction and does not sacrifice other ligaments or tendons in the foot.     

Effect of the deformation parameters on the forces in the tool during wire-drawing

An estimate is given of the magnitude of the radial forces acting on the working cone and sizing section of a draw plate in relation to the values of the main parameters in the shaping operation (the draft and friction’ the angle of the working cone’ counter-tension’ and the strain-hardening coefficient of the metal being processed).     

Effect of selected movement skills on positive self-concept

36 boys and 36 girls in 4 fourth grades were exposed to basketball movement conditions which included the skills of dribble, chest pass, lay-up, pivot, guarding, and two-hand set shot. Eight 1/2-hr. treatment periods were spread evenly over 4 wk. and took place within the regularly assigned school physical education period. Two class groups, which included 9 boys and 9 girls each, were randomly assigned by class to an experimental group which received treatment while two class groups were assigned by class to the control group. No differences between changes in self-concept as estimated by the Piers-Harris scale for treatment and control conditions were significant.     

Effect of coating of aluminum carboxymethylcellulose beads on the release and bioavailability of diclofenac sodium

Menière's disease and fluctuating hearing loss are related to labyrinthine fluid pressure variations. The development of a new indirect method of analysis of the tympanic membrane displacement during the stapedial reflex, using the Marchbanks Measurements System (MMS 10), allows us to study inner ear fluid pressure during these pathological conditions. In this study, measurements with this method were made in four groups of patients: a control group with normal hearing (n=7), stable sensorineural hearing loss (n=9), fluctuating hearing loss (n=8), and Menière's disease (n=25). Results show, first, a good relationship between the recording of negative curves, suggesting a high pressure, and the acute episodes of fluctuating hearing loss; and, secondly, in the case of Menière's disease two types of situation: positive and negative curves suggesting normal and high pressures, respectively.