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Biomedical subjects

F A Meyer

Publications and source records attributed to F A Meyer.

14 recordsLinked to original sources
PubMed1990

Synergistic, additive, and antagonistic effects of interleukin-1 beta, tumor necrosis factor alpha, and gamma-interferon on prostaglandin E, hyaluronic acid, and collagenase production by cultured synovial fibroblasts.

The effects of binary combinations of the recombinant human cytokines, interleukin-1 beta (rHuIL-1 beta), tumor necrosis factor alpha (rHuTNF alpha), and gamma-interferon (rHu gamma-IFN) on the production of prostaglandin E (PGE), hyaluronic acid (HA), and collagenase by human synovial fibroblasts in culture were investigated. All 3 were stimulated by rHuIL-1 beta and rHuTNF alpha alone, but not by rHu gamma-IFN. Stimulation with rHuIL-1 beta and rHuTNF alpha occurred at femtomolar and picomolar concentrations, respectively, and maximal stimulation by rHuIL-1 beta was several times greater than that by rHuTNF alpha. Stimulation of PGE and collagenase production with rHuIL-1 beta or rHuTNF alpha was depressed by rHu gamma-IFN, depending on the concentration used. In contrast, stimulation of HA production with rHuIL-1 beta or rHuTNF alpha was unaffected or increased somewhat with rHu gamma-IFN. Combinations of rHuIL-1 beta or rHuTNF alpha had marked synergistic effects on PGE and collagenase production. However, when rHuIL-1 beta effects were maximal, rHuTNF alpha had an additive effect. These cytokines had only additive effects on HA production, however, and when rHuIL-1 beta effects were maximal, rHuTNF alpha produced no further stimulation. These data suggest that the secretory activities of synovial fibroblasts can be influenced by a combination of cytokines and is dependent on the type of cytokine present and its concentration.

Cells, Cultured↗
PubMed1990

Modulation of the effects of interleukin-1 on glycosaminoglycan synthesis by the urine-derived interleukin-1 inhibitor, but not by interleukin-6.

Interleukin-1 (IL-1) has been shown to regulate glycosaminoglycan (GAG) synthesis. We therefore investigated whether an IL-1 inhibitor or IL-6 modulates IL-1 biologic activities in human synovial cells and cultured articular cartilage. We found that in the presence of a constant amount of IL-1 beta, stimulation of hyaluronic acid (HA) synthesis by the IL-1 inhibitor was inhibited in a dose-dependent manner. Similarly, the decrease in sulfated GAG synthesis induced by IL-1 was reversed by the addition of the IL-1 inhibitor. In contrast, IL-6 did not affect the production of HA, prostaglandin E2, or collagenase in synovial cells, nor did it affect GAG in organ cultures when tested in the presence or absence of IL-1 beta. Hence, IL-6 was ineffective in modulating IL-1 bioactivities on HA or sulfated GAG synthesis. These results emphasize the importance of IL-1 and IL-1 inhibitor in connective tissue destruction and raise questions concerning the role of IL-6 in this pathogenesis.

Cartilage, Articular↗
PubMed1979

Mucociliary transference rate and mucus viscoelasticity dependence on dynamic storage and loss modulus.

Various samples of estrous bovine cervical mucus were collected, and their dynamic viscoelastic properties were determined at between 2.7 and 4.4 rad/s. Comparing the loss modulus with the rigidity (storage) modulus for the samples taken, the former was found to increase markedly as the latter increased. Limited exposure of mucus to increased temperatures removed crosslinks, whereas treatment with glutaraldehyde introduced additional ones. In the case of one sample, the number of crosslinks was altered in this way. As the number of crosslinks decreased or increased, the storage modulus decreased or increased, but the loss modulus remained relatively unaffected. The transference (ability to move particle loads) of native and modified samples on the ciliated epithelium of a frog palate depleted of mucus was determined. All data for transference rate correlated against changes in the storage modulus. The rate was maximal for a storage modulus of 1.6 dynes.cm-2 and decreased rather sharply to either side of this value. No such correlation could be found against the loss modulus. In fact, whereas very different values of the loss modulus corresponded to the same storage modulus, the transference rate was the same. Hence, the storage rather than the loss modulus determines transference rate.

Animals↗
PubMed1978

Structure and function of mucus.

A glycoprotein building block is common to mammalian mucins. This structure is composed of several protein chains having the same sequence. The carbohydrate side chains, which constitute over three-quarters of the weight, coat only some two-thirds of the backbone chain. The bare protein chains are linked by disulphide bridges and can be digested away with trypsin. Either procedure rapidly solubilizes mucus and results in a structural unit of about 500 000 molecular weight. Mucus solubilizes spontaneously. The first size unit which reaches solution is about 15 X 10(6) molecular weight but continues to break down further. Mechanical agitation considerably speeds up this process. The gel-like character which is an essential feature of mucus--which cannot otherwise act as transport coupler--is thus a transient phenomenon. The problem of how such a structure can arise from the building blocks known to be available is discussed.

Amino Acid Sequence↗
PubMed1977

Structural investigation of loose connective tissue by using a series of dextran fractions as non-interacting macromolecular probes.

The ability of the uncharged open-coil dextran molecules to penetrate tissue space, without coil-shape change, was utilized to probe (by partitioning experiments) the structural arrangement of the collagen-fibre network and the proteoglycan system. Hyaluronidase digests most of the proteoglycans away and enables the respective contributions to the exclusion volume to be evaluated by using a series of different-molecular-weight dextrans. It appears that the major part of the exclusion volume is due to the collagen-fibril as a rod and the dextran coil as an impenetrable sphere. The additional exclusion due to the proteoglycans could be accounted for by a set of points (regions of high proteoglycan-segment density) over which the dextran coild cannot pass. These points are an average of 50 nm apart and are indicative of local extensive entanglement of high-molecular-weight proteoglycans with each other. Reasons are given why these entanglements could not act as cross-links in long-term elastic loading of the tissue.

Connective Tissue↗
PubMed1976

Aging and the interstitial content of loose connective tissue. A brief note.

The concentration of hyaluronic acid which is the fixed loose connective tissue component determining water and other potentials in the interstitium remains constant with age. Since the collagen fiber network in the native tissue state is unstressed, changes in collagen fiber morphology and in collagen content with age have no influence.

Aging↗
PubMed1975

On the role of sialic acid in the rheological properties of mucus.

The importance of sialic acid in the rheological properties of mucus has been investigated. Both bovine cervical mucus, which is a gel, and the structural glycoprotein derived from it were studied before and after treatment with neuraminidase which selectively cleaves terminal sialic acid residues. The storage modulus, viscosity and circular dichroism spectrum were all essentially changed after removal of the sialic acid. These results would indicate that removal of sialic acid does not affect the physical structure of the glycoprotein and it is concluded that sialic acid has no significant role in the rheological properties of cervical mucus.

Animals↗
PubMedDate not supplied

Clearance of middle ear effusions by the mucociliary system.

There are two extreme types of middle ear effusion leading to hearing loss (a) a rubber-like effusion seen in secretory otitis media and (b) a water-like effusion seen in serous otitis media. The possibility is considered that the degree of crosslinking in these two extreme cases is the basis of an altered mucus transport rate that leads to an accumulation of effusions and hence impaired hearing. It has been shown (King et al., 1974) that the requisite rheological property for transport activity is not unique to mucus structural macromolecules but is found with other polymeric systems that are loosely crosslinked e.g. guaran, polyacrylamide, gelatin and agarose. Studies on one of these systems guaran, indicate that the transport rate is dependent on the degree of crosslinking with a maximum rate found close to the gel point, i.e. in a region where there are very few crosslinks per macromolecule. The finding that mucus from different mucociliary epithelial sources involves a chemically similar structural glycoprotein suggests that differences observed in transport rate between various mucus samples are more likely due to differences observed in transport rate between various mucus samples are more likely due to differences in crosslinking than chemical variations of the glycoprotein units.

Animals↗