ECG of the month.
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Anesthesia, Inhalation↗
Biomedical subjects
D E Mason
Publications and source records attributed to D E Mason.
Spinal decompensation in Cotrel-Dubousset instrumentation.
Forty-one patients with idiopathic scoliosis having a primary right thoracic and a compensatory left lumbar curve underwent posterior spinal fusion of the primary curve only. Twenty-four patients had instrumentation with a Harrington rod or variant, and 17 patients underwent Cotrel-Dubousset instrumentation. Decompensation occurred postoperatively when the apex of the thoracic curve was located on or to the left of the center sacral line. There was no statistically significant change in the lumbosacral portion of the lumbar curve from the apex to the lumbosacral junction in both groups. Curve correction occurred cephalad to the apex of the lumbar curve, and not along the center sacral line. The decompensation rate was 4% for Harrington rod instrumentation and variants and 41% for Cotrel-Dubousset instrumentation. Cotrel-Dubousset instrumentation translated the apex of the thoracic curve 1.5 cm farther to the left than Harrington rod instrumentation and variants. When the apex of the lumbar curve is 2 cm or greater to the left of the center sacral line, the patient's spine will decompensate to the left, centered over the apex of the lumbar curve.
Arthrodesis↗
Occipito-atlantal translation in Down's syndrome.
Several cases of occipito-atlantal instability have been reported in patients with Down's syndrome. However, standards for radiographic measurement and normal values for translational motion at the occiput-C1 level have not been established for the Down's patient. A retrospective analysis of 102 flexion and extension lateral cervical spine radiographs of 73 patients with Down's syndrome was performed. Patients with congenital cervical spine anomalies, C1-C2 instability, or previous neck surgery were excluded. Occiput-C1 translation was measured by the technique described by Wiesel and Rothman. In normal adult patients, occiput-C1 translation should be no more than 1 mm by this method. Analysis of the data demonstrated a range of 0 to 10 mm, with a mean of 2.62 mm and a standard deviation of +/- 1.94 mm. Only 30 sets of films (29%) representing 27 patients (37%) showed anteroposterior translation of 1 mm or less. This laxity was not dependent on patient age in the current study group. A review of these patients' medical records did not disclose any evidence of impaired neurologic function related to cervical spine instability. The authors' data suggest that the prevalence and magnitude of occipito-atlantal instability in Down's syndrome is greater than previously appreciated.
Adolescent↗
Side effects of etomidate in dogs.
Intravenous administration of etomidate, a nonbarbiturate sedative hypnotic, induced excitement, myoclonus, pain on injection, vomiting, and apnea during induction of anesthesia in 20 experimental dogs and 70 hospitalized dogs. The dogs had excitement and purposeless muscle movements during recovery from anesthesia. The frequency and severity of the side effects were markedly attenuated or eliminated by the administration of diazepam, acepromazine, or morphine prior to etomidate administration.
Acepromazine↗
Identical achondroplastic twins born to normal parents: a case report and review of the literature.
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Achondroplasia↗
Isoproterenol- and salbutamol-induced relaxation of acetylcholine- and histamine-induced contraction of equine trachealis muscle in vitro.
Strips of trachealis muscle were dissected from the midcervical portion of the trachea of horses that were free of respiratory tract disease, and the overlying epithelium and mucosa were removed. Muscle strips were suspended in tissue baths that were filled with Krebs-bicarbonate solution, aerated with 5% CO2 in oxygen and maintained at 37 C. Isometric tension was continuously recorded. The increase in active isometric tension was concentration dependent when acetylcholine (10(-9) to 10(-4) M) or histamine (10(-9) to 10(-4) M) was added to the tissue baths in 0.5-logarithmic increments. When the tissues were contracted with acetylcholine (3.1 x 10(-6) M) or histamine (10(-4) M), the decrease in active isometric tension was concentration dependent when isoproterenol (10(-9) to 10(-4) M) or salbutamol (10(-9) to 10(-4) M) was added to the tissue baths in 0.5-logarithmic increments. There was no difference between the response to isoproterenol and salbutamol when tissues from the same horses were compared whether the tissues were contracted in response to acetylcholine (3.1 x 10(-6) M) or histamine (10(-4) M). Relaxation was antagonized by 10(-6) M propranolol. The degree of relaxation obtained in these muscle strips was considerably less than that reported from other species' tracheal muscle strips that had the epithelium and mucosa intact. We concluded that equine tracheal smooth muscle contains beta-adrenoceptors that can be stimulated by either a mixed beta-1, beta-2 agonist or a selective beta-2 agonist.
Acetylcholine↗
Epithelium- and mucosa-dependent relaxation and contraction of normal equine trachealis muscle in vitro.
Strips of trachealis muscle were dissected from the mid-cervical portion of the trachea from horses that were free of respiratory tract disease. The epithelium and mucosa were removed from one group of tissues and were left intact in a second group of tissues. Each tissue was suspended in a bath filled with Krebs-bicarbonate solution that was aerated with 5% CO2 in oxygen and maintained at 37 degrees C. Isometric tension was continuously recorded. The contractile response to square-wave electrical stimulations increased as frequency (3, 5, 10, 15, 20, 25, and 30 Hz), voltage (10, 15, 18, and 25 V), and pulse duration (0.2, 0.5, 1.0, 1.5, and 2.0 ms) increased in tissues with the epithelium and mucosa intact. A stimulus of 18 V, 20 Hz, and 0.5 ms induced maximal contraction. Atropine (10(-6) M) abolished the response to 18 V and 0.5 ms at all frequencies. The increase in active isometric tension was concentration dependent when acetylcholine (10(-9) to 10(-4) M) was added to the baths in 0.5-logarithmic increments. Tissues that were contracted in response to acetylcholine (10(-5) M) had a concentration-dependent decrease in active isometric tension when isoproterenol was added to the baths in 0.5-logarithmic increments (10(-9) to 10(-4) M). The contraction and relaxation curves were qualitatively similar, but quantitatively different in tissues with and without the epithelium and mucosa. Removing the epithelium and mucosa increased the contractile response to acetylcholine at bath concentrations of 3.1 x 10(-7) M and 10(-6) M. The presence of epithelium and mucosa enhanced the magnitude of isoproterenol-induced relaxations.(ABSTRACT TRUNCATED AT 250 WORDS)
Acetylcholine↗
Response of equine airway smooth muscle to acetylcholine and electrical stimulation in vitro.
Smooth muscle strips from the midcervical portion of the trachea and bronchial smooth muscle strips from third-generation airways of horses were placed in tissue baths, and isometric contractile force was measured. Active force was measured in response to electrical stimulation and exogenous acetylcholine. Square-wave electrical stimuli were applied at various voltages (10, 12, 15, 18, 20, 25 V), frequencies (3, 5, 10, 15, 20, 25, 30 Hz), and pulse durations (0.2, 0.5, 1.0, 1.5, 2.0 ms). Isometric contractile force increased as voltage, frequency, and pulse duration increased. Maximal contractile response to electrical stimulation was obtained at 18 V, 25 Hz, and 0.5 ms. Atropine (10(-6)M) or tetrodotoxin (3 x 10(-6)M) blocked the contraction, indicating that the contractile response was attributable to the release of neurotransmitter from cholinergic nerves. Cumulative concentration-response curves to acetylcholine (10(-9)M through 10(-4)M) were determined. Isometric contractile force increased as acetylcholine concentration increased. There was a significant (P less than 0.05) difference in the 50% effective dose for acetylcholine in tracheal smooth muscle and bronchial smooth muscle. The mean (+/- SD) contractile response to maximal electrical stimulus was 89% (+/- 7.4%) of that in response to 10(-4)M acetylcholine in tracheal smooth muscle and was 68% (+/- 10.4%) of the response to 10(-4)M acetylcholine in bronchial smooth muscle.
Acetylcholine↗
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↗
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↗
Sinusitus with a behavioral presentation.
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Child↗
A method for the short-term in vitro cultivation of the chick embryo on liquid media.
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Animals↗
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↗
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↗