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M I Ryder

Publications and source records attributed to M I Ryder.

33 records · Page 2Linked to original sources
PubMed1986

The cytoskeleton of the cynomolgus monkey trabecular cell. I. General considerations.

Many cellular functions involve the complex network of actin filaments, microtubules, and intermediate filaments collectively known as the cytoskeleton. Stereo transmission electron microscopic observations of whole cynomolgus monkey trabecular cells, which were extracted, S-1 labeled, and critical-point dried, were employed to simultaneously identify these three major cytoskeletal systems and visualize their three-dimensional nature. A double fluorescence technique for actin and microtubules was used to provide a broad view of cytoskeletal relationships within the cell. Actin microfilaments were the most prominent elements of the cytoskeleton. They appeared as bundles in stress fibers. Between stress fiber bundles, a continuous meshwork of microfilaments and intermediate filaments could be seen. Numerous microtubules radiated from the centriole region to the cell periphery. This comprehensive overview of the cytoskeleton of the cynomolgus monkey trabecular cell can be used to understand structure-function relationships of the trabecular cell cytoskeleton and its influence on outflow facility.

Actins↗
PubMed1986

The cytoskeleton of the cynomolgus monkey trabecular cell. II. Influence of cytoskeleton-active drugs.

The effects of cytochalasin B (10(-6) M and 10(-5) M), taxol (10(-5) M), and colchicine (10(-5) M) on the cytoskeleton of cynomolgus monkey trabecular cells were examined with Nomarski observations, fluorescent labeling as well as extraction, S-1 labeling, and critical-point drying. Changes in actin, microtubules, and intermediate filaments, the three major cytoskeletal systems, were correlated with changes in the overall shape and organization of the monkey trabecular cell. Incubation with cytochalasin B caused a marked alteration on actin filament structure, as well as cell shape and cytoskeletal organization. Effects on microtubule structure were noted with taxol, nocodozole, or colchicine; however, no marked changes in overall cell shape or other cytoskeletal structures were observed. These studies demonstrate the importance of actin filaments in regulating the shape and cytoskeletal organization of cynomolgus monkey trabecular cells.

Actins↗
PubMed1985

Angiotensin-converting enzyme activity in human aqueous humor.

We measured aqueous angiotensin-converting enzyme (ACE) activity in 37 patients. Patients with granulomatous uveitis and probable sarcoidosis (based on increased serum ACE activity or characteristic radiologic findings) had a significant increase in aqueous ACE activity compared with normal subjects. Aqueous ACE activity was also significantly elevated in patients with sarcoid who had normal serum ACE activity. We believe that measurement of aqueous ACE activity should be considered in patients with uveitis who have normal serum ACE activity and are suspected of having sarcoidosis.

Adult↗
PubMed1984

The organization of actin filaments in human polymorphonuclear leukocytes.

Actin constitutes a major component of the cytoskeleton of human polymorphonuclear leukocytes (PMNs). In this study, we present a comprehensive view of the organization of actin in various PMN regions and functional states. Transmission electron microscopic observations were made on whole mount, migrating, and phagocytizing PMNs. Positive identification of actin filaments was made through S-1 myosin subfragment labeling. In all PMNs studied, actin filaments were primarily organized as a three-dimensional meshwork. The density of this meshwork was greatest within the cell cortex. At peripheral regions of nonpolarized (viz., no distinct head or tail region) and polarized PMNs, actin filaments organized into parallel bundles or overlapping arcs. These bundles or arcs were oriented either perpendicular or parallel to the cell periphery. At the base of the PMN, actin filaments converged upon dense, plaquelike condensations. This latter pattern of actin organization was also observed in some pseudopods at the cell front and in phagocytic processes engulfing bacteria. In areas of internalized bacteria, the surrounding actin appeared as a loose meshwork. Treatment of PMNs with the antiactin drug, cytochalasin B, revealed shearing of the peripheral actin meshwork, condensation of the meshwork around the nuclear region, and dissolution of the basal plaquelike condensations.

Actins↗
PubMed1984

Bactericidal action of bicarbonate ion on selected periodontal pathogenic microorganisms.

Organisms representative of soil, skin and fecal flora and of supragingival and subgingival flora were tested for inhibition of growth and killing by various salts (NaHCO3, NaCl, MgSO4). The antimicrobial activities of KHCO3, NaF, sodium lauryl sulfate (SLS) and chloramine T were also compared with that of NaHCO3, and the rate at which NaHCO3 exerts its bactericidal effect was studied. Suspected periodontal pathogens were more susceptible to salts than were control non-oral bacteria. Supragingival plaque organisms showed intermediate susceptibility. Periodontal pathogens were more susceptible to NaHCO3 than to NaCl; NaHCO3 and KHCO3 showed similar activity against all strains tested. Accordingly, the antibacterial activity of NaHCO3 is not simply an osmotic effect and is due to the bicarbonate ion. NaF, SLS and chloramine T had greater antimicrobial activity than NaHCO3. Supragingival bacteria required at least 6-hour exposure to 1.0 M NaHCO3 to produce 99% lethality (decrease colony-forming units by 2 log10), whereas selected periodontal pathogens were killed more rapidly (30-120 minutes). The higher the concentration of bicarbonate, the faster the lethality. Morphologic examination by transmission electron microscopy of organisms exposed to bactericidal salt concentrations revealed marked fibrillar condensations within the cytoplasm and shrinkage of the cytoplasm from the outer membrane. For NaHCO3 to be clinically effective, a high concentration must be introduced into the periodontal pocket and maintained there long enough to kill periodontal pathogens. Furthermore, NaHCO3 must be reapplied often enough to prevent recolonization by these pathogens. An advantage of NaHCO3 over NaF, SLS and other antimicrobial agents is its safety, availability and low cost.

Anti-Infective Agents, Local↗
PubMed1982

The cytoskeleton of human polymorphonuclear leukocytes: phagocytosis and degranulation.

Current evidence indicates that polymorphonuclear leukocyte (PMN) chemotaxis and phagocytosis are effected by an actin-myosin contractile system. However, the structural relationship of the contractile cytoskeleton to cell motility is still in question. In addition, while evidence suggests that microtubules are responsible for orientation during chemotaxis, the role of microtubules in degranulation is unresolved. To determine the organizational relationship between these cytoskeletal elements and phagocytosis, we examined whole-mount preparations of PMNs engulfing bacteria. These preparations were examined in the transmission electron microscope (EM) and photographed as stereo pairs. Two important observations were made. First, there was an increased density of cytoskeletal elements in the pseudopod surrounding bacteria. Second, microtubule elements were intimately associated with lysosomal granules, vesicles, and phagosomes. Lysosomal granules and vesicles aligned along microtubules and clustered around phagosomes. This suggests that the microtubules may provide a tracking mechanism whereby lysosomes are specifically parceled out to phagocytic vacuoles. These results also suggest that phagocytosis and degranulation may involve different effector mechanisms.

Cell Movement↗
PubMed1981

The adherence to bone by cytoplasmic elements of osteoclast.

The intimate association observed between osteoclasts and bone has suggested that these cells may be adherent to the bony surface. We investigated this cell-surface relationship in parathyroid hormone-stimulated bone explants following applications of biophysically-induced cell detachment forces. Bone surfaces adjacent to disrupted osteoclasts were examined with transmission electron microscopy for the presence of residual cell membrane elements. Results of this study provide evidence for the adherence of osteoclasts to bony surfaces and implicate elements of both clear zone and ruffled border as cell-membrane bonded sites.

Animals↗
PubMedDate not supplied

Nicotine effects on neutrophil F-actin formation and calcium release: implications for tobacco use and pulmonary diseases.

Alterations in neutrophil functions by tobacco components may play a pivotal role in pulmonary emphysema. This study examined the role of nicotine in altering F-actin formation and calcium (Ca2+) release (two early events in neutrophil motility). The effects of these alterations on the motile function of phagocytosis were also examined. Human peripheral neutrophils from medically healthy nonsmoking subjects were incubated with nicotine at concentrations normally encountered during acute exposure to cigarette smoke (10(-2) to 10(-5) M) and/or the chemotactic peptide FLPEP (10(-7) M). Relative F-actin stain was determined by NBD phallacidin staining followed by flow cytometry. Intracellular Ca2+ was determined by INDO-1 AM loading followed by emission ratio quantitation by fluorometry. Phagocytosis was determined by the % phagocytic cells with carboxylated microspheres. Incubation of neutrophils with varying concentrations of nicotine resulted in a significant elevation of the relative F-actin stain at 30 s at 10(-2) and 10(-3) M (p < .05, ANOVA) and at 30 min at 10(-2) to 10(-4) M (p < 0.05). In time course studies with 10(-7) M FLPEP stimulation, there was a approximately 325% rise in relative F-actin stain at 30-60 s, followed by a gradual decrease to near baseline levels. There was an immediate rise in Ca2+ to approximately 150% over baseline values, followed by a gradual decrease to baseline. By contrast, stimulation with nicotine demonstrated a approximately 105% increase in relative F-actin staining at 10(-2) M (p < .001, ANOVA) and a smaller increase at 10(-3) M, which remained elevated up to 600 s. Intracellular Ca2+ levels also rose in a dose-dependent manner with an increased of 700% over baseline with 10(-2) M nicotine, and remained elevated up to 600 s. Coincubation with both FLPEP and nicotine demonstrated additive effects in relative F-actin staining at both maximal and submaximal concentrations. Preincubation with 10(-2) or 10(-3) M nicotine suppressed the % phagocytic cells by 32% and 16%, respectively (p < .001, ANOVA) with only a 1-4% reduction in cell viability (trypan blue exclusion). The results demonstrate that the concentration of nicotine during acute cigarette exposure can directly stimulate neutrophil F-actin formation and intracellular Ca2+ release by a mechanism different from peptide stimulation. The alteration of these two pivotal neutrophil signaling events by nicotine may in turn alter other neutrophil functions in tobacco-related pulmonary emphysema.

Actins↗