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Biomedical subjects

T H Moss

Publications and source records attributed to T H Moss.

At least 37 records · Page 2Linked to original sources
PubMed1981

A comparative scanning electron-microscopical study of endoneurial collagen around normal mouse nerve fibres, nerve fibres following crush injury and nerve fibres of the dystonic mouse mutant (dt/dt).

The endoneurial collagen sheath around teased nerve fibres following crush injury was studied by scanning electron microscopy and compared with uninjured sciatic nerve fibres and with fibres from the dystonic mutant mouse. Following crush injury the endoneurial collagen became more abundant than seen in untreated nerve fibres and formed large, seperate and longitudinally oriented bundles. However, by four weeks post injury the sheath regained a normal external appearance. Mutant nerve fibres were also associated with more than the usual amount of collagen, but the sheaths were more disorganised, with a marked disorientation and irregular aggregation of collagen, and these abnormalities were not confined to obviously degenerating or demyelinated regions of the fibres. The dystonic abnormalities of the endoneurial sheath may be important in the mechanism of the neuropathy.

Animals↗
PubMed1981

Segmental demyelination in the peripheral nerves of mice affected by a hereditary neuropathy (dystonia musculorum).

A teased fibre and electron-microscopical study was carried out on the sciatic nerves of mice affected with the peripheral neuropathy in dystonia musculorum. Widespread segmental demyelination was present in all the nerves. Focal axon swellings were also seen, but were relatively scarce and similar in appearance to post-traumatic reactive swellings. The variability of dystonic internodal lengths was indicative of segmental demyelination rather than axonal degeneration. The largely motor fibres of the phrenic nerve were seen to undergo a similar degenerative process, but with a later onset and more gradual progression. Segmental demyelination was found to be present before axon swellings and other degenerative changes became visible in developing phrenic nerve. Demyelination is thus an important pathological process in dystonia musculorum, and the present observations are consistent with a primary segmental demyelinating disorder in dystonic peripheral nerve.

Animals↗
PubMed1981

Schwann cell involvement in the neurological lesion of the dystonic mutant mouse. A nerve grafting study.

Schwann cell function in the dystonic mutant mouse was studied by grafting peripheral nerve from normal into affected littermates of a C57/BL (Fa.) dt dystonic mouse colony and vice versa. In a control experiment, only unaffected animals of the colony were used, and nerve isografts were found to be ultrastructurally indistinguishable from normal nerve autografts. In addition, the isografts showed no features of the lymphocytic inflammatory rejection reaction observed in normal nerve allografts, and there was evidence that donor Schwann cells remained viable and were active in all isografts examined. When nerve isografts from affected dystonic mutants were implanted into normal littermate nerves, the normal host axons regenerating through the grafted region acquired degenerative changes characteristic of naturally occurring dystonic peripheral nerve. These changes were not seen in the host axons regenerating either outside the dystonic graft regions, or more distally in the host nerve stumps. When normal nerve isografts were implanted into affected dystonic mutant nerves, the dystonic axons regenerated through the normal graft region and became normally myelinated. It is concluded that an underlying Schwann cell defect may be responsible for the abnormalities of the dystonic mouse peripheral neuropathy.

Animals↗
PubMed1978

The magnetic susceptibility of cytochrome oxidase in the 4.2-1.5 K range.

Sixteen low temperature measurements on eight independent cytochrome oxidase samples from two separate laboratories have yielded magnetic susceptibility data compatible with a model of spin-coupled iron and copper ions, as presented in the preceding paper (Tweedle, M.F., Wilson, L.J., García-Iñiguez, L., Babcock, G. T., and Palmer, G. (1978) J. Biol. Chem. 253, 8065-8071). The data in the 1.5-77 K range match those attained at higher temperatures and the predictions of the spin-coupled model. Measurements on reduced samples confirm the high spin nature of one iron atom. No obvious uncoupling of the antiferromagnetic Fe-Cu interaction is detected in partly reduced samples.

Copper↗
PubMed1977

A focus for biophysical research in energy problems.

There is widespread agreement that solar energy is the most promising long-range energy source. However, contemporary technology for bulk energy storage is so primitive that full use of the inevitably erratic solar energy flux is severely limited. Biological systems have perfected methods of storing solar energy for later use in periods of darkness, and it is argued in this symposium presentation that there are many frontiers in biophysics related to the solar energy storage problem. Moreover, the conceivable biological storage systems span a wide range of technology, with appropriate applications in societies of widely varying degrees of industrial development. Use of biological systems to produce hydrogen from solar energy may be among the most versatile of these applications. The entire problem of bioconversion of solar energy presents an excellent example of how the needs for basic scientific understanding and application engineering can be very tightly interwoven.

Bacteria↗
PubMed1975

Magnetic studies of the four-iron high-potential, non-heme protein from Chromatium vinosum.

Extensive EPR studies on high-potential, iron-sulfur protein from Chromatium vinosum indicate that the singular spectrum of this four-iron, non-heme protein consists of a superposition of three distinct signals; namely, two principal signals of equal weight, one reflecting axial and the other rhombic symmetry, and a third nearly isotropic minority component. In addition, magnetic susceptibility experiments on two oxidation states of the protein from 4.2 to approx. 260 degrees K indicate antiferromagnetic exchange coupling between iron atoms. Possible origins of the complex EPR signals are discussed, and a preferred model that is consistent with EPR, magnetic susceptibility, NMR, X-ray, and Mössbauer data is presented.

Bacterial Proteins↗
PubMed1975

The copper coordination group in "blue" copper proteins: evidence from resonance Raman spectra.

Tunable dye laser excitation in the intense similar to 600-nm absorption band of azurin, plastocyanin, and ceruloplasmin provides resonance enhanced Raman spectra. They consist of a complex set of bands, at least three or four in number, between 350 and 473 cm-1, which are assignable to Cu-N or Cu-O bond stretching, and a weak band near 270 cm-1, which probably arises from Cu-S stretching. A weak band at 765 cm-1 found in plastocyanin may arise from C-S stretching. Analysis of the Raman intensity pattern, as well as of the nature of the resonant electronic transition, leads to a model of the "blue" copper site involving approximately trigonal-bipyramidal coordination, with a sulfur and two nitrogen ligands in the equatorial plane, and less strongly bound nitrogen or oxygen ligands at axial positions. This arrangement would be well poised for stabilization of Cu(I) upon reduction.

Azurin↗
PubMed1975

The magnetic susceptibility of reduced cytochrome P-450-cam.

The primary electron acceptor of Photosystem II has a midpoint oxidation-reduction potential of +95 mV at pH 7.0 in Photosystem II chloroplast fragments prepared by digitonin treatment. The midpoint potential of the acceptor has a pH dependence of -60 mV/pH unit. At concentrations that inhibit oxygen evolution, o-phenanthroline shifts the midpoint potential of the primary acceptor by +70 mV. The shifted potential retains the same dependence on pH. The effect of o-phenanthroline suggests that it interacts directly with the primary electron acceptor of Photosystem II in a manner similar to that reported previously for the primary electron acceptor in purple photosynthetic bacteria.

Binding Sites↗
PubMed1975

Magnetic and spectroscopic probes for FeOFe linkages in hemin systems.

Magnetic and spectroscopic properties of mu-oxo-bis-hemins from natural and structurally related porphyrins were investigated as probes for ascertaining the presence or absence of FeIII-O-FeIII linkages between hemin moieties of hemeproteins. Magnetic susceptibilities of solids from 2.2 to 293 degrees K were investigated. The data fit the temperature variations expected for a pair of antiferromagnetically coupled S = 5/2, iron (III) porphyrins with J values of 175, 190, 195, 205, and 210 degrees K for deuterohemins with hydrogen, vinyl, 2'-ethoxycarbonylcyclopropyl, acetyl, propionyl, and ethyl 2,4-substituents, respectively. This magnetic character is reflected in PMR spectra that exhibit resonances with far less broadening and paramagnetic shift than is the case for monomeric high-spin hemins. Only impurities are seen in EPR spectra, which serve effectively in monitoring the magnetic purity of preparations. An infrared active asymmetric stretching frequency characteristic of the FeOFe linkage can be identified by substitution of 160 by 180. Electronic spectra are highly characteristic with poorly resolved absorption bands. The substituents on the porphyrin ring exert significant, but usually not large, electronic and steric effects on these properties. Solvent effects were relatively small and no firm evidence for binding of ligands trans to bridging oxygen was found. The uniqueness of these physical properties and their low sensitivity to changes in porphyrin structure or medium facilitates the identification of mu-oxo linkage in hemins or oxidized hemeproteins.

Binding Sites↗