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Biomedical subjects

D E Mason

Publications and source records attributed to D E Mason.

30 records · Page 2Linked to original sources
PubMed1988

Innervation of crab-eating monkey trachealis muscle determined in vitro.

Strips of smooth muscle from the cervical tracheae of six adult male crab-eating monkeys (Macaca fascicularis) were studied in jacketed 25 ml organ baths filled with Krebs-bicarbonate solution maintained at 37 degrees C and gassed with 5% CO2 in oxygen. Isometric tissue tension increased in response to electrical field stimulation (18 V, 25 Hz, 0.5 msec), norepinephrine in the presence of propranolol, acetylcholine and histamine. Atropine abolished the contractile response to electrical stimulation. Tissues that were contracted with acetylcholine or pretreated with atropine then contracted with histamine relaxed when stimulated electrically. The relaxation was unaffected by propranolol but was abolished by tetrodotoxin. Isoproterenol relaxed tissues that were contracted with histamine, but failed to relax histamine-contracted tissues that had been pretreated with propranolol. Norepinephrine did not change isometric tension in untreated tissues or tissues pretreated with phentolamine. These results demonstrate the presence of excitatory and inhibitory nerves and noninnervated beta-adrenergic receptors in macaque trachealis. The excitatory nerves appear to be cholinergic. The inhibitory response to electrical stimulation is not mediated through muscarinic cholinergic or beta-adrenergic receptors. The inhibitory response to electrical field stimulation was likely mediated through nonadrenergic noncholinergic nerves.

Acetylcholine↗
PubMed1987

Arterial blood gas tensions in the horse during recovery from anesthesia.

The effects of body position and postoperative oxygen supplementation on arterial blood gas tensions (PaO2 and PaCO2) and pH were examined in clinically normal adult horses during recovery from halothane anesthesia. Hypoxemia developed during recovery from anesthesia in spite of adequate alveolar ventilation in horses without postanesthetic oxygen supplementation. Hypoxemia developed in horses positioned in left lateral or right lateral recumbency, and in horses that were rolled to the opposite side during the recovery period. Arterial blood gas tensions were not significantly (P greater than 0.05) different between horses insufflated with 100% oxygen at the rate of 10 L/min during recovery and horses that did not receive oxygen supplementation during the recovery period. Horses that received 100% oxygen at the rate of 50 L/min through a demand valve had arterial blood gas tensions similar to those in standing awake horses.

Adult↗
PubMedDate not supplied

Occult fracture of the calcaneus in toddlers.

Five children 14-33 months of age were treated for calcaneal fractures. All had a history of trauma with limping or refusal to walk. Physical examination could not localize the fracture. Initial radiographs were negative. There were no signs of systemic illness. They were treated with long-leg casts. Radiographs after 2 weeks revealed an arc of sclerosis across the tuberosity of the calcaneus. In no case was a bone scan instrumental in making the diagnosis. Awareness of calcaneal fractures in the child younger than 36 months can prevent the routine use of bone scans to make the diagnosis.

Calcaneus↗
PubMedDate not supplied

Estimation of the lumbar curve magnitude with correction of the right thoracic curve in idiopathic scoliosis.

A simple formula was proposed to estimate the magnitude of the postoperative uninstrumented lumbar curve with correction of the right thoracic curve in idiopathic scoliosis. This formula is as follows: PLC < or = LC - 0.5(TC - BTC) (PLC, predicted postoperative standing lumbar Cobb angle; LC, preoperative standing lumbar Cobb angle; TC, preoperative standing thoracic Cobb angle; BTC, preoperative supine lateral bending thoracic Cobb angle). Sixty-five patients' preoperative and postoperative radiographic measurements were taken, and of these 45 had measurements taken after > or = 12 months of follow-up. Multiple regression (R) value for the proposed formula postoperatively was 0.8048 and at > or = 1 year follow-up was 0.6869.

Adolescent↗
PubMedDate not supplied

Congenital absence of a lumbar pedicle presenting as back pain in children.

Four children with back pain were shown to have a congenital absence of a lumbar pedicle. Computed tomography scanning was the most helpful diagnostic test. A modification of the classification of Tiyaworabun et al. for congenital absence of a pedicle in the cervical spine is suggested.

Adolescent↗
PubMedDate not supplied

Dysplasia epiphysealis hemimelica: diagnosis and treatment.

Clinical features and radiographic findings of eight patients with dysplasia epiphysealis hemimelica are described. In all patients, a single lower extremity was involved. The most common sites of involvement were the distal tibia and the distal femur. Magnetic resonance imaging was beneficial in determining a plane of separation between the accessory ossification center and the normal epiphysis. If the lesion is extraarticular, simple excision of the mass yields favorable results. If the lesion is intraarticular, an osteotomy may be needed to correct an angular deformity. Recurrence of the deformity is common.

Adolescent↗
PubMedDate not supplied

Excision of herniated nucleus pulposus in children and adolescents.

Eighty-eight patients were treated at the Alfred I. duPont Institute for disc disease from 1940 to 1989. Forty-eight patients, with an average age of 16 years, underwent discectomy. Twenty-three patients were followed for an average of 6 years after initial presentation. Thirteen patients, with an average age of 15 years, and who had radiographic documentation of disc disease, were treated nonoperatively. Eight patients were followed for an average of 6.3 years. The results of discectomy were rated as excellent or good in 91% of the patients, and poor in 9% at follow-up. In the patients treated nonoperatively, the results were rated as excellent or good in 25%, and poor in 75%. Our 6 year follow-up study suggests that discectomy yields excellent to good long-term results in children and adolescents.

Adolescent↗
PubMedDate not supplied

Posterior spinal arthrodesis for atlantoaxial instability in Down syndrome.

Nine children with Down syndrome who had atlantoaxial instability underwent posterior spinal fusion. At follow-up, all patients had stabilization or improvement of their neurologic symptoms. Evaluation of the spine using flexion and lateral radiographs, as well as selective cineradiography, showed no instability over the fused area or adjacent motion segments. Stable fibrous union with no clinical significance was noted in three of the nine patients. We recommend posterior spinal fusion in situ with external immobilization as the safest and most effective means of surgical stabilization in the patient with Down syndrome who has symptomatic atlantoaxial instability.

Adolescent↗
PubMedDate not supplied

Blood gas values during intermittent positive pressure ventilation and spontaneous ventilation in 160 anesthetized horses positioned in lateral or dorsal recumbency.

One hundred sixty horses were anesthetized with xylazine, guaifenesin, thiamylal, and halothane for elective soft tissue and orthopedic procedures. Horses were randomly assigned to one of four groups. Group 1 (n = 40): Horses positioned in lateral (LRG1; n = 20) or dorsal (DRG1; n = 20) recumbency breathed spontaneously throughout anesthesia. Group 2 (n = 40): Intermittent positive pressure ventilation (IPPV) was instituted throughout anesthesia in horses positioned in lateral (LRG2; n = 20) or dorsal (DRG2; n = 20) recumbency. Group 3 (n = 40): Horses positioned in lateral (LRG3; n = 20) or dorsal (DRG3; n = 20) recumbency breathed spontaneously for the first half of anesthesia and intermittent positive pressure ventilation was instituted for the second half of anesthesia. Group 4 (n = 40): Intermittent positive pressure ventilation was instituted for the first half of anesthesia in horses positioned in lateral (LRG4; n = 20) or dorsal (DRG4; n = 20) recumbency. Spontaneous ventilation (SV) occured for the second half of anesthesia. The mean time of anesthesia was not significantly different within or between groups. The mean time of SV and IPPV was not significantly different in groups 3 and 4. Variables analyzed included pH, PaCO2, PaO2, and P(A-a)O2 (calculated). Spontaneous ventilation resulted in significantly higher PaCO2 and P(A-a)O2 values and significantly lower PaO2 values in LRG1 and DRG1 horses compared with LRG2 and DRG2 horses. Intermittent positive pressure ventilation resulted in normocarbia and significantly lower P(A-a)O2 values in LRG2 and DRG2 horses. In LRG2 the PaO2 values significantly increased from 20 minutes after induction to the end of anesthesia. The PaO2 and P(A-a)O2 values were not significantly different from the beginning of anesthesia after IPPV in DRG2 or DRG3. The PaO2 values significantly decreased and the P(A-a)O2 values significantly increased after return to SV in horses in LRG4 and DRG4. The PaO2 values were lowest and the P(A-a)O2 values were highest in all horses positioned in dorsal recumbency compared with lateral recumbency and in SV horses compared with IPPV horses. The pH changes paralleled the changes in PaCO2. Blood gas values during right versus left lateral recumbency in all groups were also evaluated. The PaO2 values were significantly lower and the P(A-a)O2 values were significantly higher during SV in horses positioned in left lateral (LRLG1) compared with right lateral (LRRG1) recumbency.(ABSTRACT TRUNCATED AT 400 WORDS)

Anesthesia, Intravenous↗
PubMedDate not supplied

Age of closure of the neurocentral cartilage in the thoracic spine.

We reviewed magnetic resonance images (MRIs) of 91 patients to estimate the chronologic age of closure of the neurocentral cartilage in the thoracic spine. The neurocentral cartilage on MRI appeared low signal in both T1- and T2-weighted images. It was thick and clearly identified in younger patients but was thin and vague in older patients. The neurocentral cartilage closed at 11-16 years in female patients and at 12-16 years in male patients.

Adolescent↗