Dominant mutations causing alterations in acetyl-coenzyme A carboxylase confer tolerance to cyclohexanedione and aryloxyphenoxypropionate herbicides in maize.

A partially dominant mutation exhibiting increased tolerance to cyclohexanedione and aryloxyphenoxypropionate herbicides was isolated by exposing susceptible maize (Zea mays) tissue cultures to increasingly inhibitory concentrations of sethoxydim (a cyclohexanedione). The selected tissue culture (S2) was greater than 40-fold more tolerant to sethoxydim and 20-fold more tolerant to haloxyfop (an aryloxyphenoxypropionate) than the nonselected wild-type tissue culture. Regenerated S2 plants were heterozygous for the mutant allele and exhibited a high-level, but not complete, tolerance to both herbicides. Homozygous mutant families derived by self-pollinating the regenerated S2 plants exhibited no injury after treatment with 0.8 kg of sethoxydim per ha, which was greater than 16-fold the rate lethal to wild-type plants. Acetyl-coenzyme A carboxylase (ACCase; EC 6.4.1.2) is the target enzyme of cyclohexanedione and aryloxyphenoxypropionate herbicides. ACCase activities of the nonselected wild-type and homozygous mutant seedlings were similar in the absence of herbicide. ACCase activity from homozygous tolerant plants required greater than 100-fold more sethoxydim and 16-fold more haloxyfop for 50% inhibition than ACCase from wild-type plants. These results indicate that tolerance to sethoxydim and haloxyfop is controlled by a partially dominant nuclear mutation encoding a herbicide-insensitive alteration in maize ACCase.     

Long-term results of homograft valves in extracardiac conduits

Between 1971 and 1986, 335 patients received various extracardiac valved conduits between one of the heart chambers and the pulmonary arteries. The group of patients who received aortic homograft conduits and survived the operation were analysed in detail. The age varied between 9 days and 18 years (mean 7.1 ± 0.7 years), weight 2.4 kg–63.5 kg (mean 17.8 ± 10.8 kg). The diameter of the conduit used was 10–30 mm (mean 20.8 mm). Multivariate analysis revealed a highly significant model (P < 0.005) which showed that the time interval between harvesting and use of the homograft (P < 0.02) and the earlier date of operation (P < 0.05) were the major risk factors for obstruction. Homografts used within 3 weeks of harvesting had freedom from obstruction of 79% at 8 years; homografts used between 3–6 weeks had freedom from obstruction of only 55% at 8 years. Homografts used alone performed significantly better than those extended with woven Dacron tubes. At 10 years, 93% of homografts used alone were free of obstruction compared to 52% of homografts extended with a Dacron tube. We conclude that aortic homografts used within 3 weeks of harvesting provide a reasonably durable conduit for a period of 12 years. Longer storage, and extension of the homograft with a woven Dacron tube should be avoided.     

Spondylometaphyseal dysplasia, corner fracture type: a heritable condition associated with coxa vara

The authors present the radiographic features of a previously incompletely delineated bone dysplasia, which they call spondylometaphyseal dysplasia, corner fracture type. This is a dominant heritable condition associated with short stature and developmental coxa vara. The progressive hip deformity usually causes significant disability requiring surgical correction. Developmental coxa vara, simulated corner fractures of long tubular bones, and vertebral body abnormalities result in a diagnostic constellation. Knowledge of these distinctive radiologic features allows accurate diagnosis, which in turn should lead to appropriate genetic counseling and possibly to earlier, more efficacious surgical treatment of the coxa vara.     

Tyrosine promotes oxidative stress in cerebral cortex of young rats

Tyrosine accumulates in inborn errors of tyrosine catabolism, especially in tyrosinemia type II, where tyrosine levels are highly elevated in tissues and physiological fluids of affected patients. In tyrosinemia type II, high levels of tyrosine are correlated with eyes, skin and central nervous system disturbances. Considering that the mechanisms of brain damage in these disorders are poorly known, in the present study, we investigated whether oxidative stress is elicited by l-tyrosine in cerebral cortex homogenates of 14-day-old Wistar rats. The in vitro effect of 0.1-4.0mM l-tyrosine was studied on the following oxidative stress parameters: total radical-trapping antioxidant potential (TRAP), total antioxidant reactivity (TAR), ascorbic acid content, reduced glutathione (GSH) content, spontaneous chemiluminescence, thiobarbituric acid-reactive substances (TBA-RS), thiol-disulfide redox state (SH/SS ratio), protein carbonyl content, formation of DNA-protein cross-links, and the activities of the enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glucose-6-phosphate dehydrogenase (G6PDH). TRAP, TAR, ascorbic acid content, SH/SS ratio and CAT activity were significantly diminished, while formation of DNA-protein cross-link was significantly enhanced by l-tyrosine in vitro. In contrast, l-tyrosine did not affect the other parameters of oxidative stress evaluated. These results indicate that l-tyrosine decreases enzymatic and non-enzymatic antioxidant defenses, changes the redox state and stimulates DNA damage in cerebral cortex of young rats in vitro. This suggests that oxidative stress may represent a pathophysiological mechanism in tyrosinemic patients, in which this amino acid accumulates.     

Ulnar nerve injuries of the hand producing intrinsic muscle denervation on magnetic resonance imaging

Muscle and nerve injuries in the hand may be difficult to detect and diagnose clinically. Two cases are reported in which magnetic resonance imaging showed ulnar nerve injury and intrinsic hand muscle denervation. The clinical, anatomical and radiological features of injury to the deep motor branch of the ulnar nerve and associated muscle denervation are discussed and illustrated.     

Indium-111 labeled platelet deposition following transfemoral angiography

The incidence of thromboembolitic events in patients undergoing transfemoral angiography was examined using indium-111 labeled platelets. Twenty-seven patients received approximately 300 muCi of autologous labeled platelets at least 3 hours before angiography and were scanned with a gamma camera immediately before and after angiography. All patients were free of clinically obvious complications in the 1-2 day period after angiography. Our results showed evidence of platelet deposition at 21 sites other than the puncture site in 12 (44%) patients. Most platelet deposition (54%) occurred along the region between the puncture site and the aortic bifurcation; 24% occurred at sites not traversed by the catheter. At the puncture site itself, there was substantial platelet uptake in 44% of patients. This study indicates the need for further work in determining the most suitable catheter material and in assessing the efficacy of other measures such as anticoagulant or antiplatelet therapy.     

Thoracic outlet syndrome: evaluation with CT

Diagnosis of the thoracic outlet syndrome is often difficult, particularly in patients without osseous abnormalities on plain radiographs. The radiographic and computed tomographic (CT) findings were reviewed from 27 patients with thoracic outlet syndrome and 21 normal subjects. The plain radiographs and CT scans were assessed by two independent observers without awareness of the clinical history. Fifteen patients with thoracic outlet syndrome had osseous abnormalities (anomalous cervical ribs; abnormally long, drooping C-7 transverse processes) identifiable on plain radiographs. CT did not provide further diagnostic information in the patients with abnormal radiographs. Eight of 12 patients (66%) with normal plain radiographs had abnormal findings on CT scans, consisting of impingement of the C-7 transverse process on the scalene triangle or anteromedial aspect of the middle scalene muscle. Only two of 21 control patients (9.5%) displayed this CT abnormality (P less than .01). CT may be useful in patients with symptoms suggestive of thoracic outlet syndrome and no osseous abnormalities on plain radiographs.     

Incidence and management of airway problems in the CHARGE Association

The airway problems associated with anaesthesia in patients with the CHARGE Association have been underreported. We undertook a retrospective review of 50 cases, of which anaesthetic records were available for 37 patients. Apart from choanal atresia and cleft lip and palate, 56% of patients has some other upper airway abnormality. There appeared to be greater difficulty in tracheal intubation with increase in age in four patients. The incidence and management of airway abnormalities are discussed.     

Tongue and oropharynx: findings on MR imaging

Ten healthy subjects and 44 patients with diseases of the tongue or oropharynx were studied with magnetic resonance (MR) imaging. Axial, coronal, and sagittal images with a thickness of 4 mm were obtained with a pixel size of 0.75 X 0.75 mm on a 256 matrix. Nineteen of the patients underwent computed tomography (CT). Nine of those patients later had surgery, and the specimens were obtained for organ sectioning. These three studies as well as clinical history and physical examination findings were correlated. MR imaging was equal to or better than CT in those patients having both examinations. However, neither CT nor MR allowed recognition of histologic features or detection of microscopic spread of disease. Direct coronal and sagittal imaging planes on MR imaging allowed visualization of intrinsic tongue musculature, not possible with CT; this was important in recognizing subtle tumor extension. For these reasons, MR is the imaging method of choice for studying diseases of the tongue and oropharynx.