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C A Munro

Publications and source records attributed to C A Munro.

23 records · Page 2Linked to original sources
PubMed1998

End-Organ reinnervation does not prevent axonal degeneration in nerve allografts following immunosuppression withdrawal.

Previous work indicated that appropriate end-organ reinnervation fails to influence axonal degeneration in nerve allografts following immunosuppression withdrawal. In the present study, we examined if differences existed in axonal degeneration when axons regenerated across nerve allografts are allowed or completely denied end-organ reinnervation. Two ACI rat nerve allografts (3 cm long) were sutured into gaps created in both peroneal nerves in Lewis rats. In the right leg, the distal end of the graft was connected to the distal host nerve stump to allow end-organ reinnervation. In the left leg, the distal end was turned back and double ligated (unconnected) to prevent end-organ reinnervation. Rats received Cyclosporin A daily for 12 weeks to allow for regeneration and were sacrificed at 16 (n = 5) or 18 (n = 5) weeks following engraftment to assess axonal degeneration following immunosuppression withdrawal. Five Lewis rats receiving autografts served as control and were sacrificed at 12 weeks. Morphometric analysis was performed. In the control group (autografts) the cross-sectional area of and the number of myelinated fibres in the unconnected grafts was double that of the connected grafts, suggesting a sprouting effect. There was a tenfold reduction in the mean number of fibres at weeks 16 and 18 in the allografts compared to controls, without any significant differences in the connected versus unconnected sides. End-organ reinnervation decreases sprouting of axons within the graft but does not protect axons from degeneration following immunosuppression withdrawal.

Journal Article↗
PubMed1997

Motor and sensory specificity of host nerve axons influence nerve allograft rejection.

Previous studies have shown both survival and loss of regenerated host axons within nerve allograft segments after withdrawal of Cyclosporin A (CsA) immunosuppression. We hypothesized that the nature of end-organ reinnervation may influence the response of the axon, with survival of axons for appropriate innervation vs degeneration for inappropriate innervation. The rat femoral nerve model was chosen, as it has approximately equal sensory (S) and motor (M) divisions. Four ACI rat peroneal nerve allografts were sutured in straight (right leg: MM and SS) or switched (left leg; MS and SM) orientation in each femoral nerve transection gap in each Lewis rat recipient. Rats received CsA for 8 weeks to allow end-organ reinnervation, after which immunosuppression was discontinued. Rats were killed at various times thereafter, and underwent histologic and morphometric analysis of the graft segment axons. The regenerated axon population in the allograft reflected the nerve of origin: significantly more but smaller fibers when the proximal nerve was sensory and fewer but larger fibers when the proximal nerve was motor. After CsA withdrawal, there was a marked decrease of host axons as part of an ensuing rejection episode. The overall proportional decrease of axons was similar across all nerve orientation groups and, therefore, did not appear to be influenced by the nerve of origin or by the end-organ. However, the sensory proximal groups (SS and SM) contained more mature, noninjured fibers, while the motor proximal groups (MM and MS) contained significantly more degeneration and newly regenerating axons. We conclude that the motor or sensory nerve origin of the host axon, rather than the end-organ, influences axon survival after immunosuppression cessation. It is hypothesized that sensory axons may be more resilient while motor axons are selectively vulnerable to this second injury.

Animals↗
PubMed1978

Application of curve regeneration to the determination of electrolytes by the Flame IV Auto-Analyser using a mini-computer.

Curve regeneration is applied to the continuous-flow determination of serum Na +, K +, Cl- and CO2 by the Flame photometer IV (Technicon Corp.). A Hewlett-Packard 2100 A mini-computer is used for data acquisition. The continuous-flow parameters of both rise and fall curves are estimated from computer sampled voltage outputs over the standard profile. An additional interaction correction variable designated as Beta (beta) is described and applied to the regenerated peaks of the cresol red CO2 procedure. The phenolphthlalein CO2 methodology, showing improved flow parameters over those for the cresol red procedure is adapted for the Flame IV system. The basic program design is briefly outlined. Typical computer determined calibration curves (linear regression) and sample peak tracings for both the basic and regenerated techniques are illustrated.

Autoanalysis↗
PubMed1976

Curve prediction in automated analyses in routine laboratories.

1. The hydraulics of first- and second-generation AutoAnalyzers introduce lag and exponential deformations of the square wave signal expected from the colorimeter. These factors limit sampling rates by causing sample interaction. Curve regeneration carried out on Technicon Flame IV modules, using a digital approach, with a Hewlett-Packard 2100A computer, has successfully compensated for exponential deformation of sodium, potassium, chloride and carbon dioxide channels in routine laboratory use for one year. A sampling rate of 138/hr has been used; faster rates are possible. 2. Reduced sample and reagent consumption are benefits in addition to the increased analysis rate.

Autoanalysis↗