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D H Noyes

Publications and source records attributed to D H Noyes.

15 recordsLinked to original sources
PubMed1992

An electromechanical spinal injury technique with dynamic sensitivity.

Over the past decade, our laboratory has attempted to create a simple, accurate device that could be used to produce reliable and quantifiable spinal cord injuries in the rodent. We report here on our latest of several modifications of a spinal cord impactor that has allowed us to meet these design criteria. The impactor uses the dynamic capacity of an electromagnetic driver (Ling shaker) and a unique pattern generator to briefly compress the dorsal surface of the spinal cord at velocities that may mimic compression injuries seen in the human. Calibrated, independent transducer systems provide open-loop output of the precise movement (displacement) of the impactor probe and the force necessary to achieve a given displacement. Touch sensitivity is accomplished by vibrating the probe slightly as it approaches the dural surface. This also allows a known biomechanical starting point. This combination of improvements in sensitivity and ability to measure all components of the dynamic compression has allowed us to determine detailed biomechanical descriptors of these impact injuries with low coefficients of variation. Furthermore, such descriptors correlate highly with histopathologic and behavioral outcome measures in animal populations with a variety of injury severities.

Animals↗
PubMed1987

Correlation between parameters of spinal cord impact and resultant injury.

It is difficult and expensive to produce and maintain animals with experimental spinal cord injuries. In order to reduce the expenditure of time, money, and animals, a method of predicting the final neurologic deficit from the mechanical parameters of the initial injury is needed. An attempt was made to ascertain the mechanical parameter(s) of a spinal cord injuring impact which best predict(s) the extent of the subsequent injury. Twelve rats were laminectomized and the spinal cords contused with an impactor which recorded force and cord surface displacement. Spinal cord lesion volume was measured after killing at 21 days. The records of displacement and force were used to generate velocity, momentum, power, and energy. The maximum values of the six descriptors of the impact were checked for linear statistical correlation with lesion volume. The nonparametric correlations of the impact descriptors with gait scores from other work were also examined. All descriptors correlated at the 1% level many times; force and displacement correlated at the 1% level most of the time. The displacement of one cord surface with respect to the other was judged to be the most useful parameter because it correlated very nearly as well as force with the subsequent measures of trauma and better than the others (but perhaps not significantly better), and because it is technically easier to measure and control.

Animals↗
PubMed1987

A behavioral and anatomical analysis of spinal cord injury produced by a feedback-controlled impaction device.

In order to provide a reproducible experimental spinal cord injury with immediate feedback on the mechanical properties of the impact, we have developed an electro-mechanically driven, feedback-controlled impaction device. The device is sensitive to the characteristics of the injured tissue and allows continuous manipulation of impact force or tissue displacement. The current study describes the anatomical and behavioral outcomes of a range of impacts and examines the ability of the device to produce a consistent traumatic injury. Rats were subjected to spinal cord trauma at the midthoracic level. Group II received a wide range of impacts that were preset at a desired force level and group III received impacts preset for a constant displacement of the spinal cord surface. Group I served as laminectomy controls. Behavioral testing included assessments of general and fine locomotor skills (open field and grid walking) and postural adjustment to displacement (inclined plane). Lesion volumes and percentage area of the cord occupied by the lesion were assessed postmortem. For group II, significant correlations between the physical descriptors of the impact and the behavioral measures were observed early during the postoperative period for open field and inclined plane performance and later in the recovery period for grid walking. Lesion measures correlated significantly with impact descriptors and with behavioral measures as well. Group III showed consistent behavioral deficits which partially recovered in the postoperative interval. The behavioral results correlated well with the lesion measures for this group also. The results indicate that it is possible to produce an intermediate lesion in the rat which results in consistent recovery with a residual deficit 3 weeks postoperatively, using a device that allows for immediate assessment of the physical descriptors of impact trauma.

Animals↗
PubMed1977

Elastic response of the temporo-mandibular joint to very small forces.

The mechanical mobility of the temporo-mandibular joint (TMJ) was measured by applying small sinusoidal forces at different frequencies to the teeth and measuring the resultant motion of the teeth. Velocity/force ratios were recorded versus frequency at maxillary and mandibular teeth and the results were interpreted in terms of linear spring-mass-dashpot models. Differences in results obtained at maxillary and mandibular teeth indicate that the TMJ has an effective spring constant of 9 X 10(7) dynes/cm when excited by forces of approximately 2 X 10(3) dynes. Displacements occurring in the TMJ due to orthodontic elastics will be in the order of 20 mum which is between one and two orders of magnitude smaller than could be detected by radiography.

Adult↗
PubMed1975

Anesthesia of marmots with sodium pentobarbital, ketamine hydrochloride, and a combination of droperidol and fentanyl.

Three different anesthetics were tried on wild marmots to immobilize them sufficiently for intra-oral physiologic measurements and dental examination. Essentially the same procedure was performed or attempted on 15 animals. The droperidol (20 mg/ml) and fentanyl (0.4 mg/ml) combination gave better results than sodium pentobarbital or ketamine hydrochloride and was therefore used in most instances. We concluded that the dose rate should be adjusted to the nutritional state of the animal as well as to the absolute weight.

Anesthesia↗