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Biomedical subjects

A E Graves

Publications and source records attributed to A E Graves.

4 recordsLinked to original sources
PubMed2000

Older adults use a unique strategy to lift inertial loads with the elbow flexor muscles.

The purpose of this study was to determine the effect of age on the ability to exert steady forces and to perform steady flexion movements with the muscles that cross the elbow joint. An isometric task required subjects to exert a steady force to match a target force that was displayed on a monitor. An anisometric task required subjects to raise and lower inertial loads so that the angular displacement around the elbow joint matched a template displayed on a monitor. Steadiness was measured as the coefficient of variation of force and as the normalized standard deviation of wrist acceleration. For the isometric task, steadiness as a function of target force decreased similarly for old adults and young adults. For the anisometric task, steadiness increased as a function of the inertial load and there were significant differences caused by age. Old adults were less steady than young adults during both shortening and lengthening contractions with the lightest loads. Furthermore, old adults were least steady when performing lengthening contractions. These behaviors appear to be associated with the patterns of muscle activation. These results suggest that different neural strategies are used to control isometric and anisometric contractions performed with the elbow flexor muscles and that these strategies do not change in parallel with advancing age.

Adult↗
PubMed1997

Tracheostomy tube occlusion protocol predicts significant tracheal obstruction to air flow in patients requiring prolonged mechanical ventilation.

OBJECTIVE: This study was undertaken to test the hypothesis that a tracheal tube occlusion protocol predicts clinically important obstruction to air flow in patients requiring prolonged mechanical ventilation, making routine bronchoscopy unnecessary. DESIGN: A prospective evaluation of 75 patients who were clinically ready to be decannulated. All patients underwent the tracheal tube occlusion protocol followed by bronchoscopy. SETTING: Three hospitals affiliated with a college of medicine. PATIENTS: Over a 24-month period, 52 males and 23 females were enrolled in the study. Mean age was 55 yrs (range 25 to 85). Mean endotracheal/tracheostomy time was 2.4/8.9 wks (range 1 to 4/5 to 14). All patients were mechanically ventilated for at least 4 wks and were successfully weaned from the mechanical ventilator for at least 48 hrs. During spontaneous breathing, these data were observed: minute ventilation of < 10 L/min; resting respiratory rate of < 18 breaths/min; and arterial oxygen saturation of > 90% on 40% oxygen tracheal collar mask. The tracheal tube occlusion protocol consisted of deflating the cuff on the fenestrated tracheal tube and occluding the tube. INTERVENTIONS: Patients who developed respiratory distress when the tracheal tube was occluded were deemed to have failed the protocol. At bronchoscopy, the patients were asked to cough and hyperventilate in an attempt to forcibly reduce the cross-sectional area of the trachea. A sustained, subjectively assessed decrease of > or = 50% of the effective cross-sectional area of the trachea was considered to be an indication for intervention. MEASUREMENTS AND MAIN RESULTS: Sixty-three (84%) of 75 patients tolerated the tracheal tube occlusion protocol. Twelve (16%) of 75 patients developed signs of respiratory distress and showed decreased oxygen saturation values necessitating uncapping of the tracheal tube. All patients had some degree of tracheal injury. However, those patients who failed to tolerate the tracheal tube occlusion protocol had clinically important tracheal obstruction to air flow. CONCLUSION: A tracheal tube occlusion protocol can predict clinically important obstruction to air flow after prolonged mechanical ventilation.

Adult↗
PubMed1988

Scanning electron microscope studies of Agrobacterium tumefaciens attachment to Zea mays, Gladiolus sp., and Triticum aestivum.

Scanning electron microscope studies demonstrated that cells of Agrobacterium tumefaciens strains attach to cells on the cut surfaces of corn and wheat seedlings and to gladiolus disks. Bacterial cells attached to these monocots in the same manner as they attached to the dicots tested. Of the strains tested, A66 and T37 covered more of the cut surfaces of these monocots in a nonrandom fashion than did cells of other isolates. These bacteria attached to cells of intact monocotyledonous plants and had the greatest affinity for tissues located within the vascular bundles. They attached in large numbers to cells in these areas in all three monocots tested.

Bacterial Adhesion↗